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![10
BACKGROUND INFORMATION
10
Electricity District heating Direct fuel use
100%
100%
Agriculture
Energy and
waste management
Buildings
Transport
Industry
33
37
6
6
18
7
8
57
41
36
51
Residential buildings
61%
Non-residential buildings
39%
[Breakdown in %]
1025 Million t CO2
equivalent
324 Million t CO2
equivalent
TOWARDS CLIMATE
NEUTRAL BUILDINGS
A DESCRIPTIVE EXAMPLE In Germany, buildings
and their use account for approximately one-third of
total energy consumption and emissions. The majori-
ty of this demand is generated by living in residential
buildings and the remainder by so-called non-resi-
dential buildings, i.e. for commercial uses, trade,
and services. Only half of emissions is generated on
site by fossil fuel combustion. The other half is pro-
duced by power plants and heating stations that
supply buildings with power and district heating [1].
Residential buildings are the clear leader due to
their quantity: they constitute the majority of existing
buildings (Fig. A 1.01).
In existing residential buildings, heating comprises
the highest share of energy consumption. In non-
residential buildings, the impact of electrical power
consumption is growing. Significant energy loads
are caused by lighting, ventilation, and cooling, in
addition to use-specific appliances, such as com-
puters and production machinery (Fig. A 1.02). This
trend is emphasized in new construction, since
heating consumption is significantly lower here than
in existing buildings. As result, electrical power
consumption, particularly of household appliances
(“white goods”), is becoming the dominant factor in
residential buildings as well. Heating has a typically
high impact in central Europe’s climate, leading to a
pronounced seasonal character of energy consump-
tion profiles of buildings: annual electrical power
consumption is contrasted by high heating con-
sumption in winter, (still) predominantly covered by
fossil fuel combustion. This results in a very distinct
seasonal imbalance between consumption and
on-site solar energy provision. Addressing this im-
balance is one of the major challenges on the path
towards climate neutral architecture.
BUILDINGS ENDURE Approximately 70% of exist-
ing residential buildings in Germany are older than
30 years of age. They were built at a time when no
significant energy efficiency or energy savings
requirements were in place [2, 3]. Current annual
renovation rates hardly reach one percent. Without
additional efforts, an energy upgrade of all existing
buildings will take more than 100 years to complete.
From today’s point of view, this is much too long to
deal with finite resources or to turn around climate
change. This is why incentives for increasing renova-
tion rates, such as financial benefits or tax credits,
are of particular interest. Such incentives gain im-
portance due to rising energy costs, since these
lead to renovation measures becoming economically
feasible.
Renovations of high architectural quality can further
drive a related future market. An example for this
is the renovated “Neue Burse” dormitory at the Uni-
versity of Wuppertal. More than 600 students cur-
rently live there. In 2003 the deteriorating, 1970s-era
A 1.01](https://image.slidesharecdn.com/2457252-250606121300-1f4b8548/85/Net-Zero-Energy-Buildings-Karsten-Voss-Eike-Musall-15-320.jpg)
![11
TOWARDS CLIMATE NEUTRAL BUILDINGS
Small appliances
and other
Lighting
Hot water
Space heating
Entertainment
electronics, IT,
communications
Appliances
(white goods)
Hot water
Space heating
Other
Hot water
Space
heating
3 3
4
6
7
13
50
6
1
1
6
Air
conditioning
Cooling (esp. commercial)
Office equipment
Hot water
Process heat
Ventilation
(esp. fans)
Other motors
Lighting
Hot water
Space heating
Hot water
Processing
heat
Space
heating
Space heating
2 3
4
4
6
31
7
7
8
10
1
6
3
8
208 Million t CO2
equivalent 124 Million t CO2
equivalent
[Breakdown in %]
a b
A 1.02
A 1.03
A 1.01 Percentage and breakdown of greenhouse gas emis-
sion as CO2 equivalent in Germany. Approximately
one third of total annual emission of about one million
tonnes is attributable directly or indirectly to the build-
ing sector.
A 1.02 Structure of climate gas emission as CO2-equivalent
forexisting residential and non-residential buildings
in Germany (based on German energy survey 2004
consumption data of the “household” and “commercial,
trade, and services” sectors).
a Residential buildings
b Non-residential buildings
A 1.03 Student dormitory in the ecological model city of
Masdar City, United Arab Emirates (UAE) 2007,
Foster + Partners.
building was renovated in a two-stage approach as
part of a demonstration project. The new building
envelope meets the passive house standard. Heat
recovery ventilation contributed to a reduction of
energy consumption for technical infrastructure,
emissions, and energy costs by more than 50% [4].
The renovated building is currently one of the most
economically efficient dormitory buildings. At this
standard, occupants’ energy consumption for hot
water and electricity comprises the major share of
the energy balance, since the typical rent for student
housing includes a utility flat rate (Figs. A 1.04 and
A 1.05, p. 12).
DIFFERENT CLIMATE, DIFFERENT TASKS The
presented data exemplarily describe the situation
in Germany. This is comparable to the situation in
most central European countries. In regions with
higher annual temperatures and high humidity, air
conditioning comprises the major share of energy
consumption. This results in different consumption
profiles and energy provider structures.
In large parts of Asia and the Arab world, greater
economic dynamics cause extensive new construc-
tion activity at scales unimaginable in the current
European context. Day after day, entire cities and
urban quarters are created out of thin air, and glazed
office towers ascend ever higher into the sky. Grow-
ing prosperity causes an enormous demand for
small air conditioning units and an increase in power
consumption in existing buildings. Low or even no
requirements at all on energy consumption in new
construction constitute a wasted opportunity that
will lead to disproportionately high levels of energy
consumption in upcoming decades. In Asia, blindly
copying European or North American architecture
and construction techniques leads to inadequately
high consumption rates. This sets the wrong tone
in the pioneering spirit of these emerging markets.
Typical office buildings there consume approximate-
ly five times more energy than their average central
European counterparts.
However, the signs of the time are recognized here
as well, as early examples demonstrate: an eco-
logical model city for 50,000 inhabitants is under
construction in the United Arab Emirates as a large
scale model project for the post-oil era (see Masdar
Urban Development Project, p. 108ff.). The first
buildings are already complete (Fig. A 1.03). 2022
World Cup officials plan to build CO2 neutral soc-
cer stadiums. A pilot stadium for 500 spectators
has already been designed and completed in 2010.
Solar cells and parabolic collectors placed along
the stadium perimeter provide solar energy for
cooling. During non-service hours, the photovoltaic
system feeds energy into the power grid. During
service, the grid covers stadium peak demands
(Fig. A 1.06, p.13).](https://image.slidesharecdn.com/2457252-250606121300-1f4b8548/85/Net-Zero-Energy-Buildings-Karsten-Voss-Eike-Musall-16-320.jpg)
![12
BACKGROUND INFORMATION
1
2
3
4
1
2
3
4
1
2
3
4
Electricity
Heat
1 User
3 Hot water
2 Service technology
4 Space heating
Primary
energy
[kWh/m
2
a]
Neue Burse
0
200
250
300
150
50
100
Climate
gas
emissions
[kg/m
2
a]
Neue Burse
0
60
80
40
20
Site
energy
[kWh/m
2
a]
Neue Burse
∅ Dormitory
0
150
200
250
50
100
∅ Dormitory ∅ Dormitory
A 1.04
A 1.05
THE BUILDING SECTOR IN THE SPOTLIGHT OF
ENERGY AND CLIMATE POLICY Many architec-
tural, structural, and technical equipment designs for
constructing new, energy-efficient buildings and for
renovating existing buildings are already tried and
tested. Therefore, it is easy to understand why politi-
cal decisionmakers today particularly emphasize the
relevance of the building sector for energy savings
and climate protection regulations. It seems that
goals are easier to achieve here than in other sec-
tors. In the case of mobility, technological aspects
still dominate discussions on post-oil era sustainable
individual transport. Early electric vehicles display
difficulties, for instance during driving tests, since
currently available battery technology doesn’t yet
permit broad use. Questions on supplying emission-
free electricity at necessary scales are still unan-
swered.
The situation is different in the building sector. At
increasing scales, zero energy buildings, energy
plus buildings, and entire related housing projects
are under construction and in operation in Europe
and worldwide. The project section of this book
will illustrate the various reasons for these develop-
ments. In Europe, zero energy buildings are con-
sidered the logical continuation of a long chain of
developments from low-energy houses towards
passive houses. The claim is made that zero energy
buildings completely balance their annual energy
consumption and related CO2 emissions. Compared
to cars, the technological advantage of buildings
is their connection to the electrical power grid.
AMBITIOUS POLICY GOALS Against the back-
ground of climate change, global population in-
crease, and finite resources, it comes as no surprise
that energy policy goals are so ambitious.
At present, terminology related to net zero energy
buildings is important for strategy papers on energy
policy in many countries. This is partly due to posi-
tive connotations of the term “zero energy”. In the
context of finite resources and increasing energy
costs, it suggests independence, no costs, or an
orientation towards the future. Also, “zero” leaves
no room for discussion on quantification of suitable
parameters. The interpretation of energy parameters
as quantitative target definitions remains the domain
of experts and offers no real basis for communica-
tion with the general public. However, at first glance,
“zero” seems to doubtlessly demand highest possi-
ble standards regardless of building type or climate,
only to be superseded by the term “plus”.
EUROPEAN UNION The amendment to the EU
Energy Performance in Buildings Directive (EPBD)
prominently addresses the related subject matter.
The first directive in 2002 initiated the introduction
of integrated energy balancing methods throughout
Europe. These were required to take air condition-
ing, lighting, and use of renewable energy into
account [5]. In the 2010 recast the European Com-
mission introduced the term “near zero energy build-
ing” and specified timeframes for the implementation
of related construction standards within its member
states:
• “Article 2(2): Definitions:
Nearly zero-energy building means a building
that has a very high energy performance …. The
nearly zero or very low amount of energy required
should be covered to a very significant extent
by energy from renewable sources, including
energy from renewable sources produced on-site
or nearby.
• Article 9: Nearly Zero Energy Buildings:
Member States shall ensure that:
a) by 31 December 2020, all new buildings are
nearly zero-energy buildings; and
b) after 31 December 2018, new buildings occu-
pied and owned by public authorities are
nearly zero-energy buildings.
Member States shall draw up national plans for
increasing the number of nearly zero-energy
buildings. These national plans may include tar-
gets differentiated according to the category of
building.” [6]](https://image.slidesharecdn.com/2457252-250606121300-1f4b8548/85/Net-Zero-Energy-Buildings-Karsten-Voss-Eike-Musall-17-320.jpg)
![TOWARDS CLIMATE NEUTRAL BUILDINGS
13
A 1.06
“zero emission” or “climate neutrality.” However, this
can’t hide the fact that the focus is on energy sav-
ings, at least until an affordable, climate-neutral
energy source available on a broad scale is in sight.
The 2010 energy concept of the German federal
government states:
• “The central goal is a long term reduction of heat-
ing demands of existing buildings, in order to
attain a nearly climate-neutral stock of existing
buildings by 2050. Climate neutrality entails that
buildings have very low energy demands and that
remaining energy demands are predominantly
covered by renewable energy sources [...]
• The amendment of the Energy Savings Directive
of 2012 introduces the concept of “climate-neutral
building” as standard for all new construction until
2020 on the basis of primary energy parameters.
The related renovation roadmap for existing build-
ings set up in this amendment begins in 2020 and
leads to a step-by-step target of reducing primary
energy demands by 80% until 2050. Maintaining
cost-efficiency is required […]
• The federal government will assume a pioneering
role in reducing energy consumption for its exist-
ing and future new construction stock.” [10]
INCENTIVE CONCEPT FOR ENERGY-OPTIMIZED
CONSTRUCTION Within the Research Focus
Energy Optimized Construction, or “Energieopti-
miertes Bauen” (EnOB), the German Federal Min-
istry of Economics and Technology (BMWi) has
continually addressed energy research since 1995,
among others via multi-faceted demonstration
projects [11]. Initial zero energy and zero emis-
sion buildings can be found among numerous
administration buildings, schools, production facili-
ties, and residential buildings. This activity also
includes the successful participation of student
teams in the Solar Decathlon program in America
and Europe (see Solar Decathlon Europe, p.168ff.).
For 2011, climate neutrality and energy efficiency
are keywords for the “Architecture with Energy” prize
of the BMWi, awarded for the second time since
2009 [12].
SWITZERLAND Since 2009 the “Energieleitbild
Bau” (guiding energy paradigm for construction) of
the Swiss Association of Engineers and Architects
(Schweizerischer Ingenieur und Architektenverein, or
SIA) demands a sustainable basis for Switzerland’s
building stock as well as intelligent handling of ener-
gy resources [13]. Its implementation is based on
SIA’s “Effizienzpfad Energie” (efficiency path for en-
ergy) [14, 15] that, due to clearly specified limits and
targets, supports quantitative definition and imple-
mentation of energy-related goals for the “2000-watt
society” in the building categories of housing, office,
and education [16, 17].
As is typical in such strategy papers, interpreting
the implementation of measures and methods of
calculation are left to member states. How close
“nearly zero” to “zero” should be remains unan-
swered. The draft of the directive still contained the
phrase ”zero energy buildings”, but this was appar-
ently considered too ambitious as a goal. A provision
on the passive house standard already effectively
implemented in European countries such as Austria,
Germany, and Switzerland (there comparable with
the “MINERGIE-P” standard), was discussed, yet
rejected. While the passive house standard is de-
fined by a method of calculation [7], the concept
of a “near zero energy building” lacks authority,
while further procedures are open to interpretation
by each respective nation. Despite numerous efforts
to streamline construction standards internationally,
the respective national planning and policy context
remains decisive for related definitions. In 2011 this
process is only in its beginnings. The chapter “Ener-
gy Balancing: Practice, Standardization, and Legis-
lation” (pp. 40ff.) reflects on this subject in detail.
GERMANY The currently ongoing energy research
program [8] and the German federal government’s
energy concept, agreed upon in September 2010,
particularly address the building sector. It is remark-
able that, in both cases, the main focus is climate
protection: not “zero energy buildings,” but instead
A 1.04 The “Neue Burse” student dormitory, an award-winning
application of the passive house strategy in the renova-
tion of a 1970s-era building. University of Wuppertal,
Germany, 2003, Architect: Contor Müller Schlüter.
A 1.05 Comparison of consumption characteristics of 24 student
dormitories, 2005 to 2008 mean values in Germany
(total values) with metered values of the “Neue Burse”
dormitory from 2007 (partial target values). Typical for
residential use, thermal energy consumption for hot
water is high, and user demands dominate electricity
consumption. Primary energy factors and emission
factors according to A 2.07, p. 31.
A 1.06 CO2-neutral 500-seat model stadium for the 2022 soccer
World Cup in Qatar, 2010, Arup Associates. Solar cells
and collectors adjacent to the stadium supply energy for
solar cooling.](https://image.slidesharecdn.com/2457252-250606121300-1f4b8548/85/Net-Zero-Energy-Buildings-Karsten-Voss-Eike-Musall-18-320.jpg)
![BACKGROUND INFORMATION
14
Interim goal:
Reduce
fossil fuels
by 50% by 2050
Non-fossil fuels
Fossil fuels
Foreign energy supply
[W/Person]
2150
2100
2000 2050
1950
1900
0
4000
5000
6000
8000
3000
1000
2000
[W/Person]
USA
Western
Europe
Africa Switzerland
Bangladesh
World
0
8000
10000
12000
14000
6000
2000
4000
2000-WATT SOCIETY The 2000-watt society is a
strategy developed in the late 1990s at the Swiss
Federal Technical University in Zurich (ETH). Since
then it has become the official planning paradigm
not only of various Swiss cities and communities,
but also the federal government and several mu-
nicipalities [18]. It aims at sustainability as well
as just and balanced consumption of global re-
sources and addresses all aspects of life: consum-
er behaviour, mobility (Fig. A 1.11), recreation,
and of course, construction and housing as well.
In the 2000-watt society, 2000 W (primary energy)
of continuous power will be available per person,
which corresponds to current global average fig-
ures (Fig. A 1.07). Of this, a maximum of 500 W
may be provided by fossil fuel sources (Fig. A 1.08).
This policy entails that greenhouse-gas emissions
equivalent to one ton of CO2 [19] annually are per-
missible per person. This represents an implemen-
tation of the Intergovernmental Panel on Climate
Change (IPCC) recommendation for limiting global
warming at 2°C [20]. Swiss rates will lead to a re-
duction of the total energy consumption per person
from approximately 6500 W today to 2000 W, and
of CO2 emissions from 8.5 tons to 1 ton by 2150.
For this purpose, three-quarters of the 2150 demand
are supposed to be covered by renewable energy
sources. To reach these goals, total energy con-
sumption must be reduced by half and greenhouse-
gas emissions must be reduced by a factor of four
by 2050. The comparatively long time frame reflects
the large scale of required changes.
The 2000-watt society has found broad acceptance
in Switzerland as a concept within political programs
and within institutional documents on target specifi-
cations. The SIA has made the 2000-watt society the
basis of its “Efficiency Path for Energy.”
A PATH TOWARDS ENERGY EFFICIENCY The
Efficiency Path for Energy (“Effizienzpfad Energie”)
sets target specifications for primary energy and
for greenhouse gas emissions [21]. The targets are
set to meet preconditions for reaching the 2050 in-
terim goal of the 2000-watt society. They comprise
target values for three usage types: production
(embodied energy for production/replacement and
A 1.07
A 1.08
A 1.07 Comparison of continuous power consumption per
person.
A 1.08 2000-watt society as strategic goal.
A 1.09 The canopy structure of an open-air ice skating rink next
to the UPC Arena in Graz, Austria, features 1400 m2
of
solar collectors that have supplied over 500 MWh of
climate neutral heat into the district heating grid since
2002.
A 1.10 Various neologisms represent comparable goals in a
national context.
A 1.11 Mobility and buildings
disposal of building materials), operation (air-con-
ditioning, hot water, lighting and equipment) and
building-induced mobility (everyday mobility). Here,
production, mobility, and energy for service and op-
erations as classic use type receive equal emphasis.
The Efficiency Path for Energy permits calculation
of total energy consumption and corresponding
greenhouse gas emissions for these three use types
already at early planning phases.
AUSTRIA In Austria, the term “energy plus build-
ing” is much more prevalent than the term “zero-
energy building,” which has received attention only
since the “Energy Strategy” was presented in March
2010 [22]. One of the three pillars of this strategy
aims at the “nearly zero energy building” standard.
This standard originates in the “Building of Tomor-
row” technology program and was used as basis for
the further development of the energy plus building
concept [23].
STRATEGY PROCESS ENERGY 2050 The “Strate-
gieprozess Energie 2050” (Strategy Process Energy
2050) project initiated by the Austrian Federal
Ministry for Transport, Innovation and Technology
(BMVIT) aims at identifying possible future develop-
ments within a long-term perspective as basis for
targeted research and development projects. The
focus is on energy efficiency, renewable energy
sources, and intelligent energy systems. One of
seven focal subjects involves “Energy in Buildings”;
it envisions an integration of buildings into both
electrical and heating grids [24].
District heating in Austria dates back 60 years.
However, by 1982, supply only reached 2%. The
completion of the 1982 Act Promoting District Heat-
ing triggered growth in the development of heating
grids. A number of large projects and approximately
7400 smaller systems contributed to district heating
or local heating grids providing 19% of heating in
Austria in 2008. District heating boomed particularly
in urban areas: as the “district-heating city” of Aus-
tria, Linz boasts a supply rate of 60%, while Vienna
achieved “only” 34%. In rural areas, grid energy
sources are primarily based on regionally available
biomass [25]. Many of these regional and local](https://image.slidesharecdn.com/2457252-250606121300-1f4b8548/85/Net-Zero-Energy-Buildings-Karsten-Voss-Eike-Musall-19-320.jpg)
![TOWARDS CLIMATE NEUTRAL BUILDINGS
15
A 1.09
A 1.10
A 1.11
heating grids are also powered by large scale solar
systems. The largest feed into a heating grid in Aus-
tria takes place in Graz [26]. More than 10,000 m2
of
collectors feed approximately 4 GWh annually into
the district heating grid (Fig. A 1.09).
BUILDING OF TOMORROW For more than ten
years, the “Building of Tomorrow” research and tech-
nology program of BMVIT in Austria has been a driv-
ing force for innovation in the construction sector
[27]. This was made possible by a combination of
research grants and economic subventions. The first
program phase between 1999 and 2007 focused on
the passive house standard and low-energy solar
houses. The pioneering effect of these demonstra-
tion projects significantly contributed to Austria,
in comparison to other states of the EU, currently
having the highest density of completed passive
houses, equalling a total usable area of 3.2 million
square meters. The second phase, Building of To-
morrow Plus, started in 2008. It now concentrates
more on technologies and the implementation of
energy plus buildings and residential areas.
USA In the United States, the focus is on signifi-
cantly reducing the energy consumption of build-
ings to the point that renewable energy can meet
remaining loads. These efforts are implemented by
the Department of Energy (DOE [28]). Other organi-
zations actively pursue this goal as well, including
the American Society of Heating, Refrigeration &
Air-Conditioning Engineers (ASHRAE), the Ameri-
can Institute of Architects (AIA), and the U.S. Green
Building Council (USGBC). These energy policies
are related to the goal of increasing independence
from energy imports (Fig. A 1.07). In 2007, Congress
passed the Energy Independence and Security Act.
DOE’s current building technologies program states
[29]: “The long-term strategic goal is to create tech-
nologies and design approaches that lead to mar-
ketable zero-energy buildings by 2020 and to zero-
energy commercial buildings by 2025.” Definitions
for Net Zero Energy have been established to in-
clude all building laods and a hierarchy of energy
supply after energy efficiency has been maximized
[30, 31].
Four critical metrics have been established as part
of the definition:
• Net Zero Site Energy
The control boundary is established around
the site and includes purchased energy crossing
the boundary at the site. It includes all building
loads.
• Net Zero Source Energy
Even though the measurement point is at the
site, these values are scaled to account for ineffi-
ciencies in the supply system and reflect energy
consumption at the primary or source energy.
Currently these source-to-site weighing factors
are fixed annually and don’t account for seasonal
or time-of-day dependencies [32].
• Net Zero Emission
The balance is based on emission factors and not
primary energy.
• Net Zero Site Energy Cost
Buildings with no energy costs: consumption costs
don’t exceed income from feeding electricity into
the grid.
The new building of the Research Support Facility
completed in 2011 for the National Renewable Ener-
gy Lab (NREL) in Golden, Colorado, is currently the
largest structure claiming to be a net-zero energy
building (Fig. A 1.13, p. 16).
CANADA Canada lacks an official roadmap for
the building sector addressed towards Net ZEB.
In 2006, the Canadian government, through its Can-
ada Mortgage and Housing Corporation (CMHC),
announced the launch of the EQuilibrium Housing
Initiative (formerly known as the Net Zero Energy
Healthy Housing initiative). In the EQuilibrium hous-
ing initiative, the private and public sectors are
supposed to jointly develop homes that address
occupant health and comfort, energy efficiency,
renewable energy production, resource conserva-
tion, reduced environmental impact, and affordabili-
ty. EQuilibrium housing integrates a wide range of
technologies, strategies, products, and techniques
to reduce the environmental impact of homes to an
absolute minimum. At the same time, EQuilibrium
housing also features commercially available, on-site
renewable energy systems to provide clean energy
INFOBOX MOBILITY AND BUILDINGS Building induced
mobility is the sum of all distances travelled on foot, by vehi-
cle or aircraft and induced by a building in use. In addition
to energy used for driving vehicles, embodied energy that is
expended for the manufacture and upkeep of vehicles and
traffic infrastructure in use is taken into account. Differentia-
tion takes place between daily mobility – all distances in
connection to daily activities with maximum transit times
of three hours within typical surroundings – and non-daily
mobility – all distances in connection to day trips (transit time
of more than three hours and beyond typical surroundings)
as well as trips that include overnight accommodation. The
definition is based on Swiss average values and takes into
account the influences of different location-dependent as-
pects, or how the availability of cars or public transport fees
influence basic mobility, with correction factors. The refer-
ence values featured in the Efficiency Path for Energy apply
to daily mobility [33].
D Nullenergiehaus, Plusenergiehaus,
Nullemissionshaus
E net zero energy building, equilibrium
building, nearly zero energy building,
carbon neutral building
F bâtiment zéro énergie, les maisons
equilibrium, bâtiment à énergie positive,
bâtiment zéro émission](https://image.slidesharecdn.com/2457252-250606121300-1f4b8548/85/Net-Zero-Energy-Buildings-Karsten-Voss-Eike-Musall-20-320.jpg)
![BACKGROUND INFORMATION
16
Necessary savings [%]
0 20 40 60 80 100
59
67
6
43
44
53
54
32
73
90
91
64
77
62
43
80
96
58
Mean value
Offices
Storage (non-cooled)
Education
Retail
Exhibitions
Services
Churches
Lodging
Restaurants
Healthcare (inpatient)
Healthcare (outpatient)
Public safety
Grocery store
Nursing care
Laboratories
Storage (cooled)
5
Unoccupied
Other
A 1.12
A 1.13
and to help reduce annual consumption and costs.
The ultimate goal is a highly energy efficient build-
ing with low environmental impact that provides
healthy indoor living for its occupants and produc-
es as much energy as it consumes annually [34].
The initiative is intended to significantly increase
consumer interest in and awareness of the impor-
tant role that solar and other renewable energy
technologies can play in meeting Canada’s com-
mitment to a clean energy future and healthy com-
munities. By the beginning of 2011, there were
fifteen approved EQuilibrium projects in Canada
(see Ecoterra Home, p. 60 ff.).
ZERO ENERGY BUILDINGS ARE ENERGY-
EFFICIENT Regardless of the sources, the ener-
gy efficiency of buildings is covered – the reduction
of energy demands – is a central element of any
sustainability strategy. Even if energy demands
were covered in a climate-neutral way by renewable
energy,
• the basically finite availability of many renewable
energy sources
• often variable temporal availability (sun, wind,
water)
• manufacturing expenditure of energy converters,
and
• economic considerations
lead to a clear recognition: net zero energy buildings
are primarily energy-efficient buildings!
One American study shows this in an impressive
way [35]. If the total annual electricity consumption
of existing buildings were to be covered solely
by solar electricity generated by available rooftop
areas, an average reduction in electricity consump-
tion of almost 60% would be necessary (Fig. A 1.12).
Predominantly single-story construction prevalent in
the United States is suited for this comparison, since
the ratio of roof area per usable floor area is high.
Heating consumption isn’t even taken into account
here. Conclusion: without a consistent efficiency
strategy, a path towards net zero energy buildings
isn’t available!](https://image.slidesharecdn.com/2457252-250606121300-1f4b8548/85/Net-Zero-Energy-Buildings-Karsten-Voss-Eike-Musall-21-320.jpg)
![TOWARDS CLIMATE NEUTRAL BUILDINGS
17
District heating feed-in 0.3 kWh/m2
a
Solar yield
2.4 kWh/m2
a
District heating supply
6 kWh/m2
a
Waste heat of refrigeration
1.4 kWh/m2
a
Losses 0.3 kWh/m2
a
Heating including circulation losses
2.6 kWh/m2
a
Space heating
including distribution losses
6.6 kWh/m2
a
THE PASSIVE HOUSE In terms of energy efficien-
cy, the passive house (Passivhaus) concept has
assumed a leading position in Europe, especially
in the sector of residential construction [36]. In late
2010, this type of construction comprised build-
ings with over seven million square meters of usable
area in all of Europe. In Switzerland, the passive
house has become known under the “MINERGIE-P”
label [37]. With the development of high-perfor-
mance thermal insulation components for building
envelopes, as well as energy-efficient heating,
ventilation, and air-conditioning units, important
incentives have been set for new construction and
renovation in the past 20 years. Updating of legal
requirements will lead to components and systems
that are currently still considered special features
of passive house construction becoming future
standards for new construction and energy-related
building renovations.
Following an initial focus on a target figure for heat-
ing power and space heating demands [38], the
passive house concept for central European climates
aimed at a uniform primary energy parameter of
120 kWh/m2
[39] early on. This reflects the fact that,
if heating demands are very low, energy demands
are dominated by hot water supply and particular-
ly by the electricity consumption of household
appliances. According to the passive house plan,
more than 40% of primary energy is consumed by
household appliances (recommended PHPP value:
< 50 kWh/m2
a) [40]. Since, in most cases, more
than only electrical power is used in buildings, pri-
mary energy is more suitable as an indicator than
the sum of electricity and other energy sources such
as natural gas, oil, etc. The advantage of conversion
into primary energy is that varying energy expendi-
ture for providing electricity and heat is taken into
account. However, conversion factors aren’t physi-
cal constants, but differ according to the structure
of national electricity-generating systems (see
Fig. A 2.08, p. 31).
THE SEARCH FOR SIMPLE RULES DESPITE COM-
PLEX REQUIREMENTS In practice, the transition
to calculating energy demands based on primary
nergy is already increasing complexity for practical
applications in residential buildings. Prior to this,
specifications for maximum permissible heat transfer
coefficient values of components or of area-related
heating demands were easily comprehensible. In
contrast, interpreting primary energy limit values to
produce clear recommendations is only possible in
the context of on-site energy supply systems and
based on experience. The data in the project exam-
ples in this book provide actual and practical solu-
tions to abstract requirements (see Projects and
Experiences, p. 56ff.).
Target definitions and energy demand calculations
for non-residential buildings are even more complex.
According to the first building directive of the EU
in 2002 [41], all member states are obligated to
adapt their national standardisation and legislation
so that electrical energy demands of lighting and
air conditioning are also taken into account within
mandatory total energy parameters. For the first
time, clients and system manufacturers have an in-
centive to consider energy efficiency as a decisive
developmental aspect in these sectors. Such a pa-
rameter system has been in place only in Switzer-
land since the beginning of the 1990s: the SIA 380-4
– Electrical Energy in Building Construction directive
[42]. Due to the diversity of uses, the total energy
parameters for non-residential buildings are differen-
tiated to varying degrees according to type. For
mixed use, total energy parameters are determined
from data for individual building parts, emphasized
according to area.
Against this background, demonstration projects
play an important pioneering role. Beyond calcu-
lation results, they offer a basis for defining total
energy target values for national standards via
operative performance. One excellent example is
the Forum Chriesbach research and administrative
building, completed in late 2006 in the Swiss munici-
pality of Dübendorf and awarded numerous prizes
(Figs. A 1.14 and A 1.15, p. 17) [43, 44]. The waste
heat recovery from commercial chillers and the
output of a 50 m2
tube collector system cover ap-
proximately 40% of heating demands. The roughly
12,000 m2
building draws just under 6 kWh/m2
a heat
from the district-heating grid. Through an earth-air
A 1.12 Necessary reduction in electricity consumption of exist-
ing buildings in the United States if corresponding roof-
mount photovoltaic systems are to annually balance
consumption.
A 1.13 The 1.6-MWp photovoltaic systems of the 20,500 m2
“Research Support Center” of the National Renewable
Energy Laboratory (NREL) in Golden, Colorado, USA
2011, RNL Design, aim at a zero-energy balance.
A 1.14 Energy flow diagram for the heat supply of Forum
Chriesbach based on metered values from 2007 (values
refer to a heated floor area of 11,170 m2
)
A 1.15 The Aquatic Research Institute of ETH Zurich (Eawag)
is located in the Forum Chriesbach office and research
building, conceived as a passive house building
(MINERGIE-P). Dübendorf, Switzerland 2006, Architect:
Bob Gysin + Partner, Energy planner: 3-Plan Haustech-
nik AG.
A 1.14
A 1.15](https://image.slidesharecdn.com/2457252-250606121300-1f4b8548/85/Net-Zero-Energy-Buildings-Karsten-Voss-Eike-Musall-22-320.jpg)
![BACKGROUND INFORMATION
18
Lighting
Use-specific electricity consumption
Space heating
Heat pump
Ventilation
Cooling
Primary
energy
[kWh/m
2
a]
0
600
500
100
200
300
400
A B C D E F G H I J K L M N O P Q R
Institute Production Administration
A 1.16
heat exchanger and passive cooling, the build-
ing interiors require almost no active cooling. The
power demand without central servers is just below
17 kWh/m2
a. In comparison, the output of the 77 kWp
photovoltaic system is at 6.4 kWh/m2
a annually.
For some building types, comparative studies al-
ready provide sufficient results. Primary energy
parameters of energy efficient office and adminis-
trative buildings in central European climates today
are of the order of 80 to 100 kWh/m2
a without appli-
ances and equipment. Including equipment, values
of 120 to 190 kWh/m2
a are attained during service
(Fig. A 1.16) [45, 46], as in approximately half of
typical new construction. Individual projects can
be even significantly more efficient. Economic com-
parisons of demonstration buildings show that their
investment costs are no more than 5% above those
of comparable buildings, while energy costs com-
prise only half the average value [47].
ZERO ENERGY EXTREME: SELF-SUFFICIENT
BUILDINGS At first glance, and considering these
degrees of energy efficiency, a building that can
supply its own energy seems to be just a step away.
A self-sufficient building, i.e. a building that isn’t
connected to energy infrastructure, guarantees
continuous energy supply based on the size of the
building’s own, typically solar energy system, and
particularly of energy storage devices, without re-
verting to other, external resources. Particularly in
European climates, the seasonal balance between
energy supply and demand requires significant
technical investment in energy storage. In climates
without pronounced seasonal differences, signifi-
cantly simpler concepts are possible. Designs at
scales of complex solutions for multiple buildings
and for entire residential areas are easier as well.
The aim isn’t the sum total of self-sufficient build-
ings, but instead the self-sufficiency of the entire
complex. The temporal and structural differences
in energy demands of individual buildings permit
time-related compensation, and thus, reduction of
storage volume.
SELF-SUFFICIENT HEATING SUPPLY – POSSI-
BLE, BUT BETTER NOT ENTIRELY The interior
temperature of a solid-construction passive house
typically doesn’t fall below 10 °C in central European
climate, even without any heating (Figs. A 1.17 and
A 1.18) [48]. This temperature is the result of ba-
lancing heat gains from the use of solar energy and
waste heat generated by individuals and devices
with heat losses from transmission and ventilation.
Heat storage capacity of building construction en-
sures, even during longer phases of absence of use
and at lower heat gains, that interior temperatures
don’t decline drastically or rise to extremely high
interior temperatures when solar gains are high. In
A 1.16 Measured primary energy parameters for the demon-
stration building of the EnOB development programme
(data are standardized according to heated net floor
area). For the administrative building, mean primary
energy target values are 98 kWh/m2
without and
188 kWh/m2
with use-specific consumption.
A 1.17 Adobe construction office building as passive house,
Tattendorf, Austria, 2006, Architekturbüro Reinberg
A 1.18 Cooling curve for the Tattendorf passive house. In late
2007 and early 2008 the building wasn’t occupied.
practice, interior temperatures have upper limits
based on user behaviour (window ventilation, sun
protection), so that during times of high solar intake
unlimited storage charging isn’t possible. Neverthe-
less, would it be possible to increase heat storage
capacity of necessary structural elements of a build-
ing to such a degree that interior temperatures no
longer fall below 20 °C solely by passive use of solar
energy?
PHASE CHANGE MATERIALS Phase change ma-
terials (PCM) in the form of micro-encapsulated par-
affins can be added to mineral materials of walls and
ceilings. Such paraffins (waxes) absorb heat within a
defined temperature range, such as from 21 to 22°C
during the melting process, and discharge this heat
again during solidification. Special salt hydrates
have even higher heat storage capacities and are
being processed as components e.g. in suspended
ceilings. Calculations show, however, that even if all
available surfaces in a building were improved in
this way or an extremely solid construction type was
selected, the resulting storage capacity would in-
deed contribute to a further reduction of heating de-
mands, but would not make heating systems redun-
dant. In summer, in connection with sun screens and
nighttime ventilation, more significant effects and
even entirely avoiding active cooling systems are
possible (see company headquarters in Kemptthal,
p. 120ff.). This is primarily because heat is stored](https://image.slidesharecdn.com/2457252-250606121300-1f4b8548/85/Net-Zero-Energy-Buildings-Karsten-Voss-Eike-Musall-23-320.jpg)
![TOWARDS CLIMATE NEUTRAL BUILDINGS
19
19.12. 23.12. 27.12. 31.12. 04.01. 08.01.
Temperature
[°C]
-10
-5
0
5
10
15
20
25
30 Exterior temperature
Interior temperature
A 1.17
A 1.18
and discharged only in daily cycles. These systems
don’t permit buffering of longer heating phases.
SOLAR COLLECTORS AND HOT-WATER STORAGE
DEVICES In active solar energy use via collectors,
a water tank serves as heat storage. As result, the
maximum acceptable interior temperature isn’t appli-
cable as the upper limit for storage temperature,
while the heat insulation of water tanks permits
longer storage phases.
A simple example, the full heating supply of a 150 m2
house for four occupants, indicates the dimensions
required [49]. This system is based on optimally
oriented flat tube collectors and a large-volume
water storage tank within the building (Figs. A 1.19
and A 1.20, p. 20). If both hot water heating and the
entire space heating demands (25 kWh/m2
a) are to
be covered by solar energy, then the required col-
lector area needs to be at least 30 m2
. Even more
importantly, the storage volume needs to be at least
50 m3
. Together with the necessary heat insulation of
the storage device, required space equals 5–10%
of the building volume. Geometric optimization is, in
practice, a very significant factor in determining how
much usable space is actually needed.
In Europe, the pioneer of self-sufficient system con-
cepts was the Jenni house in 1991 in the Swiss mu-
nicipality of Oberburg. The 200 m3
house has a col-
lector surface area of 84 m2
and a thermal energy
storage device holding 118 m3
[50]. The storage
device proved much too big. The numerous follow-
up projects mainly in Switzerland and Austria oper-
ate successfully with significantly smaller systems
supplemented by wood furnaces. Advantageously,
smaller storage devices also require lower em-
bodied energy. Considering the limited number of
charge/discharge cycles, this comprises a signifi-
cant parameter in the life cycle balancing of large
metal storage devices. Large water storage devices
made of plastic, however, haven’t proven effective
to date in terms of long-term stability, due to occa-
sionally high summer storage temperatures.
One example for solar heating with high solar frac-
tion is the residential system for the Samer Mösl
passive house residential complex in the Austrian
city of Salzburg (Figs. A 1.22 and M 1.23, p. 21) [51].
The 60 residential units were completed in 2006 by
Heimat Österreich (public housing and residential
development corporation) as public housing. The
climate-neutral heating supply is based on a solar
system with 200 m2
flat tube collectors mount on the
building’s flat roof and a 21 m3
buffer storage device
connected to a 100 kW pellet boiler. The 11 m tall
storage tank with a diameter of 1.6 m (measured
without insulation) is integrated vertically in the stair-
case and extends across all three stories plus the
basement. The solar energy system covers approxi-
mately half of heating demands.
When a system is designed to cover demands to
100% according to a location’s average climate
data, experience has shown that, depending on
actual weather patterns, energy is sufficient in one
year (no additional heating demand). However, in
the following year there can be a shortfall [52]. This
is primarily due to the sequence of sunny and cloudy
days. Long-lasting periods of bad weather or fog
are critical. Many successful projects are located in
mountain regions that experience more sunny winter
days. To omit any service gaps, the required storage
volume increases significantly. This effect impacts
hot water use first, since higher temperatures are re-
quired here than for space heating. In general, heat
storage devices for large buildings or residential
areas show better results, because the ratio of area
loss to storage volume is significantly improved.
STORAGE WITH HIGHER HEAT CAPACITY In the-
ory, alternatives to large water storage tanks exist
with higher storage densities and lower heat losses.
If one cubic meter of water is heated or cooled by
30°C, this corresponds to an energy content of
30 kWh. Such a heating process increases the heat
energy in a 50 m3
storage tank by only 1500 kWh. In
contrast, a suitable phase-change material, such as
sodium sulphate, stores approximately 100 kWh/m3
when melting at a temperature of around 30 °C and
releases this heat again during solidification. Storage
devices with thermo-chemical substances may be](https://image.slidesharecdn.com/2457252-250606121300-1f4b8548/85/Net-Zero-Energy-Buildings-Karsten-Voss-Eike-Musall-24-320.jpg)
![[Metropolia Student Project Seminar 24.5.] Zero Energy Buildings, Group B](https://cdn.slidesharecdn.com/ss_thumbnails/zeroenergybuildingsgroupb-120529021343-phpapp01-thumbnail.jpg?width=640&height=640&fit=bounds)
![[Metropolia Student Project Seminar 24.5.] Zero Energy Buildings, Group A](https://cdn.slidesharecdn.com/ss_thumbnails/zeroenergybuildings-presentation24-5-2012-120528082031-phpapp01-thumbnail.jpg?width=640&height=640&fit=bounds)
Net Zero Energy Buildings Karsten Voss Eike Musall
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- 9. 4 IMPRINT IMPRINT AUTHORS AND EDITORS KarstenVoss, Prof. Dr.-Ing.; Eike Musall, M.Sc.arch. CO-AUTHORS Andreas K. Athienitis, Prof. Ph.D.; Soara Bernard, M.Sc.arch., Dipl.-Ing.; Armin Binz, Prof.; Dylan Brady; Marko Brandes, Dipl.-Ing.; José A. Candanedo, Ph.D.; Arnulf Dinkel, Dipl.-Ing. Architekt; Sabine Erber, DI; Shane Esmore, Director & Principal Sustainability Consultant; Norbert Fisch, Univ.-Prof. Dr.-Ing.; François Garde, Prof.; Sonja Geier, DI; Michael Gies, Dipl.-Ing.; Monika Hall, Dr.-Ing.; Ferdinand Hammerer; Sebastian Herkel, Dipl.-Ing. Maschinenbau; Patrick Jung, Dipl.-Ing., Visiting Prof.; Florian Kagerer, Dipl.-Ing.; Beat Kämpfen, Dipl. Architekt eth/sia, M.A.; Jens Krause, Dipl.-Ing.; Jörg Lange, Dr.; Henrik Langehein, Dipl.-Ing.; Beatrix Lehnert, Design Manager; Aurélie Lenoir; Ingo Lütkemeyer, Prof. Dipl.-Ing. Architekt; Masa Noguchi, Ph.D., Senior Lecturer; Stefan Plesser, Dipl.-Ing. Architekt; Dietmar Riecks, Dipl.-Ing. Architekt; Audrius Ringaila, Invited Designer; Lars Rössing, Dipl.-Ing. Architekt; Tanja Siems, Prof. Dr.-Ing.; Katharina Simon, M.Sc.arch.; Armin Themessl, Ing.; Bert Tilicke, Dipl.-Ing. Architekt/Landschaftsarchitekt; Martin Ufheil, Dipl.-Ing.; David Waldren, Development Manager; Gerhard Zweier, Dipl.Ing. Architekt ASSISTANTS Melina Schulz, B.Sc.arch., M.Sc.arch.cand.; Masato Takagaki, Bachelor of Law, B.Sc.arch.cand.; Dennis Hagen, M.Sc.arch.; Jana Eggermann, B.Sc.arch.cand. FUNDING This publication was produced in the context of collaboration between experts of the International Energy Agency (IEA) in the framework of the programmes Solar Heating & Cooling (SHC, Task 40) and Energy Conservation in Buildings & Community Sys- tems (ECBCS, Annex 52) under the title “Towards Net Zero Ener- gy Solar Buildings”. The official publication is the English edition. This book and the German collaboration in the framework of the IEA were aided as part of the research initiative EnOB – Reseach for Energy-optimised Construction, in accordance with a decision of the Bundestag, by the German Federal Ministry of Economics and Technology. The Austrian collaboration in the framework of the IEA and in the production of this publication was aided by the Austrian Federal Ministry of Transport, Inno- vation and Technology, the Swiss contribution by the Swiss Federal Office of Energy. Partial funding for the translation into English was provided by: • Government of Canada's Program of Energy Research and Development (PERD) under the project management of CanmetENERGY research centre. PERD Is a federal inter- departmental program operated the Department of Natural Resources Canada. • Grocon group of companies, Australia. EDITORIAL SERVICES Editors: Cornelia Hellstern, Dipl.-Ing. (project head); Kim Ahrend, Dipl.-Ing. Architektin; Jana Rackwitz, Dipl.-Ing. Editorial assistants: Katinka Johanning, Dr.; Michaela Linder, State Certified Translator; Jakob Schoof, Dipl.-Ing. Translation into English: J. Roderick O’Donovan, B. Arch., Vienna (A) Premier Focus Inc., Waterloo, Ontario (CDN) Sevag Pogharian Design, Montreal, Quebec (CDN) Proofreading: Mark Kammerbauer, Dipl.Ing., M. Sc., Munich Drawings: Ralph Donhauser, Dipl.-Ing. Graphic design: Michael Vitzthum, Dipl.-Des. (Cover) Cornelia Hellstern, Dipl.-Ing. (Layout) DTP & Production: Roswitha Siegler, Simone Soesters Reproduction: Martin Härtl OHG, Munich Printing and binding: Kösel GmbH & Co. KG, Altusried-Krugzell This work is subject to copyright. All rights reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, recitation, reuse of illustrations and tables, broadcasting, reproduction on microfilm or in other ways and storage in data processing systems. Reproduction of any part of this work in individual cases too, is only permitted within the limits of the provisions of the valid edition of the copy- right law. A charge will be levied. Infringements will be subject to the penalty clauses of the copyright law. Bibliographic information published by the German National Library: The German National Library lists this publication in the Deutsche Nationalbibliograpfie; detailed bibliographic information is available on the Internet http://dnb.d-nb.de. Institut für internationale Architektur-Dokumentation GmbH & Co. KG Hackerbrücke 6, D-80335 Munich www.detail.de © 2013, new edition ISBN: 978-3-920034-80-5
- 10. 5 CONTENTS 5 CONTENTS A BACKGROUND INFORMATION KarstenVoss with contributions by Monika Hall, Sonja Geier and Armin Binz 1 TOWARDS CLIMATE NEUTRAL BUILDINGS 10 2 METHODICAL PRINCIPLES OF BALANCING 28 3 ENERGY BALANCING: PRACTICE, STANDARDISATION, AND LEGISLATION 40 B PROJECTS AND LESSONS LEARNED OVERVIEW OF PROJECTS AND THEIR CHARACTERISTICS – PART 1 50 Eike Musall, Karsten Voss SMALL RESIDENTIAL BUILDINGS 01 RESIDENTIAL HOUSE 56 Monika Hall, Eike Musall 02 ÉCOTERRA HOME 60 Andreas Athienitis, José Candanedo, Eike Musall 03 LIGHTHOUSE 64 Masa Noguchi, Eike Musall 04 HOME FOR LIFE 68 Eike Musall LARGE RESIDENTIAL BUILDINGS 05 KRAFTWERK B 72 Monika Hall, Eike Musall 06 RENOVATION BLAUE HEIMAT 78 Florian Kagerer, Sebastian Herkel 07 KLEEHÄUSER 84 Jörg Lange, Eike Musall, Michael Gies 08 MULTI-FAMILY DWELLING 89 Beat Kämpfen HOUSING DEVELOPMENTS 09 SOLAR COMMUNITY 94 Eike Musall, Karsten Voss 10 ENERGY PLUS COMMUNITY 100 Sonja Geier 11 BEDZED COMMUNITY 103 Masa Noguchi, Audrius Ringaila, Eike Musall CITIES 12 MASDAR URBAN DEVELOPMENT PROJECT 108 Tanja Siems, Katharina Simon, Arnulf Dinkel, Eike Musall OVERVIEW OF PROJECTS AND THEIR CHARACTERISTICS – PART 2 114 Eike Musall, Karsten Voss OFFICE BUILDINGS 13 CORPORATE HEADQUARTERS 120 Monika Hall, Eike Musall 14 WWF HEADQUARTERS 125 Eike Musall 15 OFFICE BUILDING WITH APARTMENT 129 Sonja Geier 16 PIXEL BUILDING 134 Shane Esmore, David Waldren, Dylan Brady, Beatrix Lehnert PRODUCTION AND ADMINISTRATION 17 COMPANY HEADQUARTERS 138 Stefan Plesser, Henrik Langehein, Norbert Fisch 18 ZERO EMISSIONS FACTORY 144 Dietmar Riecks, Eike Musall, Martin Ufheil EDUCATIONAL BUILDINGS 19 SCHOOL RENOVATION 150 Sabine Erber, Gerhard Zweier, Ferde Hammerer, Eike Musall 20 UNIVERSITY BUILDING 154 Aurélie Lenoir, François Garde 21 DAY CARE CENTRE 158 Bert Tilicke, Lars Rössing, Patrick Jung 22 ELEMENTARY SCHOOL 163 Ingo Lütkemeyer, Jens Krause, Marko Brandes EXPERIMENTAL BUILDINGS 23 SOLAR DECATHLON EUROPE 168 Soara Bernard C APPENDIX 178
- 11. 6 PREFACE PREFACE Discussions on theappropriate energy policy for the future and the growing concerns about climate change regularly focus on the built environment in particular. On the one hand, the construction, main- tenance, and operation of buildings throughout their life cycle consumes large amounts of energy and causes emissions. On the other hand, we are al- ready aware of and have tested measures for all kinds of buildings that can dramatically reduce the level of consumption and emissions. However, the net zero energy and plus energy buildings dealt with in this book go further than these concepts. They indicate how an equalised annual energy balance can be achieved by bringing to- gether architectural design, energy efficiency and the local use of renewables. They stand for inde- pendence from finite resources and immunity to fluctuating energy prices. A zero-carbon building does not contribute to climate change. INTERNATIONAL ENVIRONMENT In the new ver- sion of the building guidelines published in 2010 the European Union calls upon member states to introduce the energy standard “Nearly Zero Energy Building” for all new buildings by no later than the end of 2020. The building technology programme of the United States of America formulates the goals of arriving at marketable zero energy residential build- ings by 2020 and non-residential buildings by 2025. Nevertheless, standards that precisely define the goals in relation to the respective national building practice standards do not yet exist. The Swiss MIN- ERGIE-A Certificate, which was released in March 2010, has become a pioneer in this important area of establishing definitions. A proposal towards a calculation process in the context of German standardisation has been formu- lated and accompanied by a relevant calculation tool. The basic material needed to acquire a general understanding of the theme is conveyed in Section A of this book, “BACKGROUND INFORMATION”. CLIMATE NEUTRAL BUILDINGS Under extreme conditions, autonomous buildings point the way. Far removed from any kind of energy infrastructure and without a connection to an energy grid, they are generally entirely self-supplying by means of renewables. But for the broad mass of buildings connected to the grid, this can't represent the model of the future. The long-term storage of energy, in particular of electricity, is a significant technological bottleneck. Equipping buildings to produce their own electricity is not only technologically demanding, the mainte- nance of such systems is complex and expensive, which means that connecting the building to an elec- tricity grid offers a significant advantage. However, a building can only be described as climate neutral if the electricity grids are based to 100% on renewa- bles. But today and in the long term there is too little of this certified green electricity to waste it through inadequate building efficiency. The planned intro- duction of electro-mobility will increase the demand for clean electricity, allowing even less room for wastage. PROJECTS AND LESSONS LEARNED Buildings have sufficient surface area, space, and infrastruc- ture to operate their own plants to generate energy and feed it into grids. Here, photovoltaic systems and (above all, in larger and more energy intensive non-residential buildings) combined heat and power plants integrated in the building and run on biomass are suitable. Many of the projects presented in this book are so-called all-electric houses. This applies in particular to the residential buildings. Their energy systems are restricted to photovoltaic systems and heat pumps, so that electricity is their only energy source. Because net zero energy buildings manage without long-term storage of electrical energy, the national power grid takes on this function and balances seasonal fluctuations in energy generation in relation to varying energy demands. The buildings present-
- 12. PREFACE 7 7 ed in SectionB of this book, "PROJECTS AND LES- SONS LEARNED", differ clearly with regard to the extent to which this “service” for grid based balanc- ing is used and how flexibly the building energy system can react to the demands of the grids. In the future, to ensure an optimally functioning grid infra- structure, also with a substantially higher quota of electricity from renewables (smart grids), buildings will have to be more intensively integrated in genera- tion and load management than has been the case thus far. The case studies show that very high energy effi- ciency is imperative for a realistic chance of achiev- ing an equalised annual energy balance. Through the interaction of architecture, building construction, and energy technology the studies presented utilise diverse possibilities: from the geometry to the U- values of the parts of the building envelope to the performance of combined heat and power units or photovoltaic arrays. The 23 projects selected present buildings of different sizes, typologies, loca- tions, and construction methods, ranging from resi- dential and non-residential buildings to housing developments and even an entire city. Many projects use the passive house standard as their starting point, while the first renovation projects point the way towards zero energy for an existing building fabric. Designing and building a net zero energy building means that from the very start energy demand and energy generation must be consistently kept in bal- ance: If the demand in the annual sum exceeds the possibilities for energy generation, further savings must be implemented. Here, an integrated planning team of architects, structural designers, and energy engineers is the decisive and essential requirement. This book documents in detail the results of energy monitoring and the experience gained from the planning and use phases, as well as the individual steps on the way to an equalised energy balance. The fact that a number of buildings don't achieve this balance in practice emphasises the difficulty of this task and the gap between planning and reality. However, this does not reduce their value. Cross- sectional analyses of more than 50 further projects carried out all around the world supplement the overview and broaden knowledge of possible strate- gies. Research has revealed the dynamics with which the field of zero energy is currently being developed. NETWORK OF RESEARCHERS The collaboration in the international energy agency IEA titled “To- wards Net Zero Energy Solar Buildings” involves representatives of 19 nations who participate in an intensive dialogue on suitable definitions and assessment procedures, discussing the experi- ence they have gained from national demonstration projects, and publishing their findings. These activi- ties also underline the international dimensions of the theme and its growing importance. ACKNOWLEDGEMENTS We thank the numerous authors whose contributions are of such significant importance for the success of this book. With their buildings, committed clients and designers have created the conditions under which net zero energy buildings can become reality. The work on this book was assisted by the German Federal Ministry of Economics and Technology, the Swiss Federal Office of Energy, and the Austrian Federal Ministry of Transport, Innovation and Tech- nology. The English language edition is a slightly modified follow-up of the German language book published in June 2011. The translation was sup- ported by the Government of Canada's Program of Energy Research and Development as well as the Grocon group of companies in Australia. Wuppertal October 2011 Karsten Voss, Eike Musall The editors The IEA joint “Solar Heating and Cooling (SHC) Programme Task 40/Energy Conservation in Build- ings and Community Systems (ECBCS) Programme Annex 52: Towards Net-Zero Energy Solar Build- ings” (NZEBs) is a 5-year international collaboration between approximately 75 national experts from 19 nations in Europe, North America, Oceania, and Southeast Asia. It seeks to study current net-zero, near net-zero and very low energy buildings and to develop a common understanding of a harmonised international definitions framework, tools, innovative solutions and industry guidelines to support the conversion of the NZEB concept from an idea into practical reality in the marketplace. I am pleased to present the English edition of “Net-Zero Energy Buildings”, a major accomplishment in this field, and which encapsulates the many and varied concepts and views of defining net-zero energy buildings by government research organizations, international and regional research centres, academia, and in- dustry that have been discussed in this Task/Annex since its inauguration in the fall of 2008. I am confi- dent this book will find many interested readers. Varennes, Canada October 2011 Josef Ayoub Operating Agent, IEA SHC Task 40/ECBCS Annex 52, CanmetENERGY/Natural Resources Canada
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- 14. 9 CONTENTS A 1 TOWARDSCLIMATE NEUTRAL BUILDINGS 10 A DESCRIPTIVE EXAMPLE 10 AMBITIOUS POLICY GOALS 12 EUROPEAN UNION 12 GERMANY 13 SWITZERLAND 13 AUSTRIA 14 USA 15 CANADA 15 ZERO ENERGY BUILDINGS ARE ENERGY- EFFICIENT 16 ZERO ENERGY EXTREME: SELF-SUFFICIENT BUILDINGS 18 SELF-SUFFICIENT HEATING SUPPLY – POSSIBLE, BUT BETTER NOT ENTIRELY 18 SELF-SUFFICIENT POWER SUPPLY – ONLY IF NECESSARY 20 PRACTICAL APPLICATIONS OF ZERO ENERGY BUILDINGS: MORE OR LESS GRID-BASED 23 A FIRST CONCLUSION 26 A 2 METHODICAL PRINCIPLES OF BALANCING 28 INPUT/OUTPUT BALANCE 28 SOLAR CONCEPTS AND THEIR EXPANSION IN ENERGY-INTENSIVE BUILDINGS 28 MANY DIFFERENCES BETWEEN ZERO ENERGY BUILDINGS ARE HIDDEN BY DETAIL 29 THE BALANCING INDICATORS 30 PRIMARY ENERGY 30 GREENHOUSE GASES 30 ENERGY COSTS 31 DIFFERENT PRIMARY ENERGY FACTORS 31 THE BALANCE BOUNDARY 33 USE-SPECIFIC ENERGY CONSUMPTION 33 ELECTROMOBILITY 33 EXTERNAL ENERGY PRODUCTION SYSTEMS 33 THE BALANCING PERIOD 34 THE GRID OF THE FUTURE 34 THE INFLUENCE OF EMBODIED ENERGY ON THE LIFECYCLE BALANCE 34 LOAD-MATCH AS CRITERION OF DIFFEREN- TIATION 35 THE SELECTION OF BUILDING TECHNOLOGY INFLUENCES LOAD-MATCH 37 ACTUAL LOAD-MATCH IS SMALLER 37 GRID INTEGRATION 37 A 3 ENERGY BALANCING: PRACTICE, STAND- ARDISATION, AND LEGISLATION 40 GERMANY 40 LEGISLATION AND STANDARDISATION 40 CONCEPT FOR REDEFINING THE ZERO ENERGY BUILDING 42 CALCULATION TOOL 42 SWITZERLAND 42 LEGISLATION AND STANDARDISATION 43 THE MINERGIE LABEL 44 MINERGIE-A 45 MINERGIE-P AND MINERGIE-A 45 AUSTRIA 45 LEGISLATION AND STANDARDISATION 46
- 15. 10 BACKGROUND INFORMATION 10 Electricity Districtheating Direct fuel use 100% 100% Agriculture Energy and waste management Buildings Transport Industry 33 37 6 6 18 7 8 57 41 36 51 Residential buildings 61% Non-residential buildings 39% [Breakdown in %] 1025 Million t CO2 equivalent 324 Million t CO2 equivalent TOWARDS CLIMATE NEUTRAL BUILDINGS A DESCRIPTIVE EXAMPLE In Germany, buildings and their use account for approximately one-third of total energy consumption and emissions. The majori- ty of this demand is generated by living in residential buildings and the remainder by so-called non-resi- dential buildings, i.e. for commercial uses, trade, and services. Only half of emissions is generated on site by fossil fuel combustion. The other half is pro- duced by power plants and heating stations that supply buildings with power and district heating [1]. Residential buildings are the clear leader due to their quantity: they constitute the majority of existing buildings (Fig. A 1.01). In existing residential buildings, heating comprises the highest share of energy consumption. In non- residential buildings, the impact of electrical power consumption is growing. Significant energy loads are caused by lighting, ventilation, and cooling, in addition to use-specific appliances, such as com- puters and production machinery (Fig. A 1.02). This trend is emphasized in new construction, since heating consumption is significantly lower here than in existing buildings. As result, electrical power consumption, particularly of household appliances (“white goods”), is becoming the dominant factor in residential buildings as well. Heating has a typically high impact in central Europe’s climate, leading to a pronounced seasonal character of energy consump- tion profiles of buildings: annual electrical power consumption is contrasted by high heating con- sumption in winter, (still) predominantly covered by fossil fuel combustion. This results in a very distinct seasonal imbalance between consumption and on-site solar energy provision. Addressing this im- balance is one of the major challenges on the path towards climate neutral architecture. BUILDINGS ENDURE Approximately 70% of exist- ing residential buildings in Germany are older than 30 years of age. They were built at a time when no significant energy efficiency or energy savings requirements were in place [2, 3]. Current annual renovation rates hardly reach one percent. Without additional efforts, an energy upgrade of all existing buildings will take more than 100 years to complete. From today’s point of view, this is much too long to deal with finite resources or to turn around climate change. This is why incentives for increasing renova- tion rates, such as financial benefits or tax credits, are of particular interest. Such incentives gain im- portance due to rising energy costs, since these lead to renovation measures becoming economically feasible. Renovations of high architectural quality can further drive a related future market. An example for this is the renovated “Neue Burse” dormitory at the Uni- versity of Wuppertal. More than 600 students cur- rently live there. In 2003 the deteriorating, 1970s-era A 1.01
- 16. 11 TOWARDS CLIMATE NEUTRALBUILDINGS Small appliances and other Lighting Hot water Space heating Entertainment electronics, IT, communications Appliances (white goods) Hot water Space heating Other Hot water Space heating 3 3 4 6 7 13 50 6 1 1 6 Air conditioning Cooling (esp. commercial) Office equipment Hot water Process heat Ventilation (esp. fans) Other motors Lighting Hot water Space heating Hot water Processing heat Space heating Space heating 2 3 4 4 6 31 7 7 8 10 1 6 3 8 208 Million t CO2 equivalent 124 Million t CO2 equivalent [Breakdown in %] a b A 1.02 A 1.03 A 1.01 Percentage and breakdown of greenhouse gas emis- sion as CO2 equivalent in Germany. Approximately one third of total annual emission of about one million tonnes is attributable directly or indirectly to the build- ing sector. A 1.02 Structure of climate gas emission as CO2-equivalent forexisting residential and non-residential buildings in Germany (based on German energy survey 2004 consumption data of the “household” and “commercial, trade, and services” sectors). a Residential buildings b Non-residential buildings A 1.03 Student dormitory in the ecological model city of Masdar City, United Arab Emirates (UAE) 2007, Foster + Partners. building was renovated in a two-stage approach as part of a demonstration project. The new building envelope meets the passive house standard. Heat recovery ventilation contributed to a reduction of energy consumption for technical infrastructure, emissions, and energy costs by more than 50% [4]. The renovated building is currently one of the most economically efficient dormitory buildings. At this standard, occupants’ energy consumption for hot water and electricity comprises the major share of the energy balance, since the typical rent for student housing includes a utility flat rate (Figs. A 1.04 and A 1.05, p. 12). DIFFERENT CLIMATE, DIFFERENT TASKS The presented data exemplarily describe the situation in Germany. This is comparable to the situation in most central European countries. In regions with higher annual temperatures and high humidity, air conditioning comprises the major share of energy consumption. This results in different consumption profiles and energy provider structures. In large parts of Asia and the Arab world, greater economic dynamics cause extensive new construc- tion activity at scales unimaginable in the current European context. Day after day, entire cities and urban quarters are created out of thin air, and glazed office towers ascend ever higher into the sky. Grow- ing prosperity causes an enormous demand for small air conditioning units and an increase in power consumption in existing buildings. Low or even no requirements at all on energy consumption in new construction constitute a wasted opportunity that will lead to disproportionately high levels of energy consumption in upcoming decades. In Asia, blindly copying European or North American architecture and construction techniques leads to inadequately high consumption rates. This sets the wrong tone in the pioneering spirit of these emerging markets. Typical office buildings there consume approximate- ly five times more energy than their average central European counterparts. However, the signs of the time are recognized here as well, as early examples demonstrate: an eco- logical model city for 50,000 inhabitants is under construction in the United Arab Emirates as a large scale model project for the post-oil era (see Masdar Urban Development Project, p. 108ff.). The first buildings are already complete (Fig. A 1.03). 2022 World Cup officials plan to build CO2 neutral soc- cer stadiums. A pilot stadium for 500 spectators has already been designed and completed in 2010. Solar cells and parabolic collectors placed along the stadium perimeter provide solar energy for cooling. During non-service hours, the photovoltaic system feeds energy into the power grid. During service, the grid covers stadium peak demands (Fig. A 1.06, p.13).
- 17. 12 BACKGROUND INFORMATION 1 2 3 4 1 2 3 4 1 2 3 4 Electricity Heat 1 User 3Hot water 2 Service technology 4 Space heating Primary energy [kWh/m 2 a] Neue Burse 0 200 250 300 150 50 100 Climate gas emissions [kg/m 2 a] Neue Burse 0 60 80 40 20 Site energy [kWh/m 2 a] Neue Burse ∅ Dormitory 0 150 200 250 50 100 ∅ Dormitory ∅ Dormitory A 1.04 A 1.05 THE BUILDING SECTOR IN THE SPOTLIGHT OF ENERGY AND CLIMATE POLICY Many architec- tural, structural, and technical equipment designs for constructing new, energy-efficient buildings and for renovating existing buildings are already tried and tested. Therefore, it is easy to understand why politi- cal decisionmakers today particularly emphasize the relevance of the building sector for energy savings and climate protection regulations. It seems that goals are easier to achieve here than in other sec- tors. In the case of mobility, technological aspects still dominate discussions on post-oil era sustainable individual transport. Early electric vehicles display difficulties, for instance during driving tests, since currently available battery technology doesn’t yet permit broad use. Questions on supplying emission- free electricity at necessary scales are still unan- swered. The situation is different in the building sector. At increasing scales, zero energy buildings, energy plus buildings, and entire related housing projects are under construction and in operation in Europe and worldwide. The project section of this book will illustrate the various reasons for these develop- ments. In Europe, zero energy buildings are con- sidered the logical continuation of a long chain of developments from low-energy houses towards passive houses. The claim is made that zero energy buildings completely balance their annual energy consumption and related CO2 emissions. Compared to cars, the technological advantage of buildings is their connection to the electrical power grid. AMBITIOUS POLICY GOALS Against the back- ground of climate change, global population in- crease, and finite resources, it comes as no surprise that energy policy goals are so ambitious. At present, terminology related to net zero energy buildings is important for strategy papers on energy policy in many countries. This is partly due to posi- tive connotations of the term “zero energy”. In the context of finite resources and increasing energy costs, it suggests independence, no costs, or an orientation towards the future. Also, “zero” leaves no room for discussion on quantification of suitable parameters. The interpretation of energy parameters as quantitative target definitions remains the domain of experts and offers no real basis for communica- tion with the general public. However, at first glance, “zero” seems to doubtlessly demand highest possi- ble standards regardless of building type or climate, only to be superseded by the term “plus”. EUROPEAN UNION The amendment to the EU Energy Performance in Buildings Directive (EPBD) prominently addresses the related subject matter. The first directive in 2002 initiated the introduction of integrated energy balancing methods throughout Europe. These were required to take air condition- ing, lighting, and use of renewable energy into account [5]. In the 2010 recast the European Com- mission introduced the term “near zero energy build- ing” and specified timeframes for the implementation of related construction standards within its member states: • “Article 2(2): Definitions: Nearly zero-energy building means a building that has a very high energy performance …. The nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby. • Article 9: Nearly Zero Energy Buildings: Member States shall ensure that: a) by 31 December 2020, all new buildings are nearly zero-energy buildings; and b) after 31 December 2018, new buildings occu- pied and owned by public authorities are nearly zero-energy buildings. Member States shall draw up national plans for increasing the number of nearly zero-energy buildings. These national plans may include tar- gets differentiated according to the category of building.” [6]
- 18. TOWARDS CLIMATE NEUTRALBUILDINGS 13 A 1.06 “zero emission” or “climate neutrality.” However, this can’t hide the fact that the focus is on energy sav- ings, at least until an affordable, climate-neutral energy source available on a broad scale is in sight. The 2010 energy concept of the German federal government states: • “The central goal is a long term reduction of heat- ing demands of existing buildings, in order to attain a nearly climate-neutral stock of existing buildings by 2050. Climate neutrality entails that buildings have very low energy demands and that remaining energy demands are predominantly covered by renewable energy sources [...] • The amendment of the Energy Savings Directive of 2012 introduces the concept of “climate-neutral building” as standard for all new construction until 2020 on the basis of primary energy parameters. The related renovation roadmap for existing build- ings set up in this amendment begins in 2020 and leads to a step-by-step target of reducing primary energy demands by 80% until 2050. Maintaining cost-efficiency is required […] • The federal government will assume a pioneering role in reducing energy consumption for its exist- ing and future new construction stock.” [10] INCENTIVE CONCEPT FOR ENERGY-OPTIMIZED CONSTRUCTION Within the Research Focus Energy Optimized Construction, or “Energieopti- miertes Bauen” (EnOB), the German Federal Min- istry of Economics and Technology (BMWi) has continually addressed energy research since 1995, among others via multi-faceted demonstration projects [11]. Initial zero energy and zero emis- sion buildings can be found among numerous administration buildings, schools, production facili- ties, and residential buildings. This activity also includes the successful participation of student teams in the Solar Decathlon program in America and Europe (see Solar Decathlon Europe, p.168ff.). For 2011, climate neutrality and energy efficiency are keywords for the “Architecture with Energy” prize of the BMWi, awarded for the second time since 2009 [12]. SWITZERLAND Since 2009 the “Energieleitbild Bau” (guiding energy paradigm for construction) of the Swiss Association of Engineers and Architects (Schweizerischer Ingenieur und Architektenverein, or SIA) demands a sustainable basis for Switzerland’s building stock as well as intelligent handling of ener- gy resources [13]. Its implementation is based on SIA’s “Effizienzpfad Energie” (efficiency path for en- ergy) [14, 15] that, due to clearly specified limits and targets, supports quantitative definition and imple- mentation of energy-related goals for the “2000-watt society” in the building categories of housing, office, and education [16, 17]. As is typical in such strategy papers, interpreting the implementation of measures and methods of calculation are left to member states. How close “nearly zero” to “zero” should be remains unan- swered. The draft of the directive still contained the phrase ”zero energy buildings”, but this was appar- ently considered too ambitious as a goal. A provision on the passive house standard already effectively implemented in European countries such as Austria, Germany, and Switzerland (there comparable with the “MINERGIE-P” standard), was discussed, yet rejected. While the passive house standard is de- fined by a method of calculation [7], the concept of a “near zero energy building” lacks authority, while further procedures are open to interpretation by each respective nation. Despite numerous efforts to streamline construction standards internationally, the respective national planning and policy context remains decisive for related definitions. In 2011 this process is only in its beginnings. The chapter “Ener- gy Balancing: Practice, Standardization, and Legis- lation” (pp. 40ff.) reflects on this subject in detail. GERMANY The currently ongoing energy research program [8] and the German federal government’s energy concept, agreed upon in September 2010, particularly address the building sector. It is remark- able that, in both cases, the main focus is climate protection: not “zero energy buildings,” but instead A 1.04 The “Neue Burse” student dormitory, an award-winning application of the passive house strategy in the renova- tion of a 1970s-era building. University of Wuppertal, Germany, 2003, Architect: Contor Müller Schlüter. A 1.05 Comparison of consumption characteristics of 24 student dormitories, 2005 to 2008 mean values in Germany (total values) with metered values of the “Neue Burse” dormitory from 2007 (partial target values). Typical for residential use, thermal energy consumption for hot water is high, and user demands dominate electricity consumption. Primary energy factors and emission factors according to A 2.07, p. 31. A 1.06 CO2-neutral 500-seat model stadium for the 2022 soccer World Cup in Qatar, 2010, Arup Associates. Solar cells and collectors adjacent to the stadium supply energy for solar cooling.
- 19. BACKGROUND INFORMATION 14 Interim goal: Reduce fossilfuels by 50% by 2050 Non-fossil fuels Fossil fuels Foreign energy supply [W/Person] 2150 2100 2000 2050 1950 1900 0 4000 5000 6000 8000 3000 1000 2000 [W/Person] USA Western Europe Africa Switzerland Bangladesh World 0 8000 10000 12000 14000 6000 2000 4000 2000-WATT SOCIETY The 2000-watt society is a strategy developed in the late 1990s at the Swiss Federal Technical University in Zurich (ETH). Since then it has become the official planning paradigm not only of various Swiss cities and communities, but also the federal government and several mu- nicipalities [18]. It aims at sustainability as well as just and balanced consumption of global re- sources and addresses all aspects of life: consum- er behaviour, mobility (Fig. A 1.11), recreation, and of course, construction and housing as well. In the 2000-watt society, 2000 W (primary energy) of continuous power will be available per person, which corresponds to current global average fig- ures (Fig. A 1.07). Of this, a maximum of 500 W may be provided by fossil fuel sources (Fig. A 1.08). This policy entails that greenhouse-gas emissions equivalent to one ton of CO2 [19] annually are per- missible per person. This represents an implemen- tation of the Intergovernmental Panel on Climate Change (IPCC) recommendation for limiting global warming at 2°C [20]. Swiss rates will lead to a re- duction of the total energy consumption per person from approximately 6500 W today to 2000 W, and of CO2 emissions from 8.5 tons to 1 ton by 2150. For this purpose, three-quarters of the 2150 demand are supposed to be covered by renewable energy sources. To reach these goals, total energy con- sumption must be reduced by half and greenhouse- gas emissions must be reduced by a factor of four by 2050. The comparatively long time frame reflects the large scale of required changes. The 2000-watt society has found broad acceptance in Switzerland as a concept within political programs and within institutional documents on target specifi- cations. The SIA has made the 2000-watt society the basis of its “Efficiency Path for Energy.” A PATH TOWARDS ENERGY EFFICIENCY The Efficiency Path for Energy (“Effizienzpfad Energie”) sets target specifications for primary energy and for greenhouse gas emissions [21]. The targets are set to meet preconditions for reaching the 2050 in- terim goal of the 2000-watt society. They comprise target values for three usage types: production (embodied energy for production/replacement and A 1.07 A 1.08 A 1.07 Comparison of continuous power consumption per person. A 1.08 2000-watt society as strategic goal. A 1.09 The canopy structure of an open-air ice skating rink next to the UPC Arena in Graz, Austria, features 1400 m2 of solar collectors that have supplied over 500 MWh of climate neutral heat into the district heating grid since 2002. A 1.10 Various neologisms represent comparable goals in a national context. A 1.11 Mobility and buildings disposal of building materials), operation (air-con- ditioning, hot water, lighting and equipment) and building-induced mobility (everyday mobility). Here, production, mobility, and energy for service and op- erations as classic use type receive equal emphasis. The Efficiency Path for Energy permits calculation of total energy consumption and corresponding greenhouse gas emissions for these three use types already at early planning phases. AUSTRIA In Austria, the term “energy plus build- ing” is much more prevalent than the term “zero- energy building,” which has received attention only since the “Energy Strategy” was presented in March 2010 [22]. One of the three pillars of this strategy aims at the “nearly zero energy building” standard. This standard originates in the “Building of Tomor- row” technology program and was used as basis for the further development of the energy plus building concept [23]. STRATEGY PROCESS ENERGY 2050 The “Strate- gieprozess Energie 2050” (Strategy Process Energy 2050) project initiated by the Austrian Federal Ministry for Transport, Innovation and Technology (BMVIT) aims at identifying possible future develop- ments within a long-term perspective as basis for targeted research and development projects. The focus is on energy efficiency, renewable energy sources, and intelligent energy systems. One of seven focal subjects involves “Energy in Buildings”; it envisions an integration of buildings into both electrical and heating grids [24]. District heating in Austria dates back 60 years. However, by 1982, supply only reached 2%. The completion of the 1982 Act Promoting District Heat- ing triggered growth in the development of heating grids. A number of large projects and approximately 7400 smaller systems contributed to district heating or local heating grids providing 19% of heating in Austria in 2008. District heating boomed particularly in urban areas: as the “district-heating city” of Aus- tria, Linz boasts a supply rate of 60%, while Vienna achieved “only” 34%. In rural areas, grid energy sources are primarily based on regionally available biomass [25]. Many of these regional and local
- 20. TOWARDS CLIMATE NEUTRALBUILDINGS 15 A 1.09 A 1.10 A 1.11 heating grids are also powered by large scale solar systems. The largest feed into a heating grid in Aus- tria takes place in Graz [26]. More than 10,000 m2 of collectors feed approximately 4 GWh annually into the district heating grid (Fig. A 1.09). BUILDING OF TOMORROW For more than ten years, the “Building of Tomorrow” research and tech- nology program of BMVIT in Austria has been a driv- ing force for innovation in the construction sector [27]. This was made possible by a combination of research grants and economic subventions. The first program phase between 1999 and 2007 focused on the passive house standard and low-energy solar houses. The pioneering effect of these demonstra- tion projects significantly contributed to Austria, in comparison to other states of the EU, currently having the highest density of completed passive houses, equalling a total usable area of 3.2 million square meters. The second phase, Building of To- morrow Plus, started in 2008. It now concentrates more on technologies and the implementation of energy plus buildings and residential areas. USA In the United States, the focus is on signifi- cantly reducing the energy consumption of build- ings to the point that renewable energy can meet remaining loads. These efforts are implemented by the Department of Energy (DOE [28]). Other organi- zations actively pursue this goal as well, including the American Society of Heating, Refrigeration & Air-Conditioning Engineers (ASHRAE), the Ameri- can Institute of Architects (AIA), and the U.S. Green Building Council (USGBC). These energy policies are related to the goal of increasing independence from energy imports (Fig. A 1.07). In 2007, Congress passed the Energy Independence and Security Act. DOE’s current building technologies program states [29]: “The long-term strategic goal is to create tech- nologies and design approaches that lead to mar- ketable zero-energy buildings by 2020 and to zero- energy commercial buildings by 2025.” Definitions for Net Zero Energy have been established to in- clude all building laods and a hierarchy of energy supply after energy efficiency has been maximized [30, 31]. Four critical metrics have been established as part of the definition: • Net Zero Site Energy The control boundary is established around the site and includes purchased energy crossing the boundary at the site. It includes all building loads. • Net Zero Source Energy Even though the measurement point is at the site, these values are scaled to account for ineffi- ciencies in the supply system and reflect energy consumption at the primary or source energy. Currently these source-to-site weighing factors are fixed annually and don’t account for seasonal or time-of-day dependencies [32]. • Net Zero Emission The balance is based on emission factors and not primary energy. • Net Zero Site Energy Cost Buildings with no energy costs: consumption costs don’t exceed income from feeding electricity into the grid. The new building of the Research Support Facility completed in 2011 for the National Renewable Ener- gy Lab (NREL) in Golden, Colorado, is currently the largest structure claiming to be a net-zero energy building (Fig. A 1.13, p. 16). CANADA Canada lacks an official roadmap for the building sector addressed towards Net ZEB. In 2006, the Canadian government, through its Can- ada Mortgage and Housing Corporation (CMHC), announced the launch of the EQuilibrium Housing Initiative (formerly known as the Net Zero Energy Healthy Housing initiative). In the EQuilibrium hous- ing initiative, the private and public sectors are supposed to jointly develop homes that address occupant health and comfort, energy efficiency, renewable energy production, resource conserva- tion, reduced environmental impact, and affordabili- ty. EQuilibrium housing integrates a wide range of technologies, strategies, products, and techniques to reduce the environmental impact of homes to an absolute minimum. At the same time, EQuilibrium housing also features commercially available, on-site renewable energy systems to provide clean energy INFOBOX MOBILITY AND BUILDINGS Building induced mobility is the sum of all distances travelled on foot, by vehi- cle or aircraft and induced by a building in use. In addition to energy used for driving vehicles, embodied energy that is expended for the manufacture and upkeep of vehicles and traffic infrastructure in use is taken into account. Differentia- tion takes place between daily mobility – all distances in connection to daily activities with maximum transit times of three hours within typical surroundings – and non-daily mobility – all distances in connection to day trips (transit time of more than three hours and beyond typical surroundings) as well as trips that include overnight accommodation. The definition is based on Swiss average values and takes into account the influences of different location-dependent as- pects, or how the availability of cars or public transport fees influence basic mobility, with correction factors. The refer- ence values featured in the Efficiency Path for Energy apply to daily mobility [33]. D Nullenergiehaus, Plusenergiehaus, Nullemissionshaus E net zero energy building, equilibrium building, nearly zero energy building, carbon neutral building F bâtiment zéro énergie, les maisons equilibrium, bâtiment à énergie positive, bâtiment zéro émission
- 21. BACKGROUND INFORMATION 16 Necessary savings[%] 0 20 40 60 80 100 59 67 6 43 44 53 54 32 73 90 91 64 77 62 43 80 96 58 Mean value Offices Storage (non-cooled) Education Retail Exhibitions Services Churches Lodging Restaurants Healthcare (inpatient) Healthcare (outpatient) Public safety Grocery store Nursing care Laboratories Storage (cooled) 5 Unoccupied Other A 1.12 A 1.13 and to help reduce annual consumption and costs. The ultimate goal is a highly energy efficient build- ing with low environmental impact that provides healthy indoor living for its occupants and produc- es as much energy as it consumes annually [34]. The initiative is intended to significantly increase consumer interest in and awareness of the impor- tant role that solar and other renewable energy technologies can play in meeting Canada’s com- mitment to a clean energy future and healthy com- munities. By the beginning of 2011, there were fifteen approved EQuilibrium projects in Canada (see Ecoterra Home, p. 60 ff.). ZERO ENERGY BUILDINGS ARE ENERGY- EFFICIENT Regardless of the sources, the ener- gy efficiency of buildings is covered – the reduction of energy demands – is a central element of any sustainability strategy. Even if energy demands were covered in a climate-neutral way by renewable energy, • the basically finite availability of many renewable energy sources • often variable temporal availability (sun, wind, water) • manufacturing expenditure of energy converters, and • economic considerations lead to a clear recognition: net zero energy buildings are primarily energy-efficient buildings! One American study shows this in an impressive way [35]. If the total annual electricity consumption of existing buildings were to be covered solely by solar electricity generated by available rooftop areas, an average reduction in electricity consump- tion of almost 60% would be necessary (Fig. A 1.12). Predominantly single-story construction prevalent in the United States is suited for this comparison, since the ratio of roof area per usable floor area is high. Heating consumption isn’t even taken into account here. Conclusion: without a consistent efficiency strategy, a path towards net zero energy buildings isn’t available!
- 22. TOWARDS CLIMATE NEUTRALBUILDINGS 17 District heating feed-in 0.3 kWh/m2 a Solar yield 2.4 kWh/m2 a District heating supply 6 kWh/m2 a Waste heat of refrigeration 1.4 kWh/m2 a Losses 0.3 kWh/m2 a Heating including circulation losses 2.6 kWh/m2 a Space heating including distribution losses 6.6 kWh/m2 a THE PASSIVE HOUSE In terms of energy efficien- cy, the passive house (Passivhaus) concept has assumed a leading position in Europe, especially in the sector of residential construction [36]. In late 2010, this type of construction comprised build- ings with over seven million square meters of usable area in all of Europe. In Switzerland, the passive house has become known under the “MINERGIE-P” label [37]. With the development of high-perfor- mance thermal insulation components for building envelopes, as well as energy-efficient heating, ventilation, and air-conditioning units, important incentives have been set for new construction and renovation in the past 20 years. Updating of legal requirements will lead to components and systems that are currently still considered special features of passive house construction becoming future standards for new construction and energy-related building renovations. Following an initial focus on a target figure for heat- ing power and space heating demands [38], the passive house concept for central European climates aimed at a uniform primary energy parameter of 120 kWh/m2 [39] early on. This reflects the fact that, if heating demands are very low, energy demands are dominated by hot water supply and particular- ly by the electricity consumption of household appliances. According to the passive house plan, more than 40% of primary energy is consumed by household appliances (recommended PHPP value: < 50 kWh/m2 a) [40]. Since, in most cases, more than only electrical power is used in buildings, pri- mary energy is more suitable as an indicator than the sum of electricity and other energy sources such as natural gas, oil, etc. The advantage of conversion into primary energy is that varying energy expendi- ture for providing electricity and heat is taken into account. However, conversion factors aren’t physi- cal constants, but differ according to the structure of national electricity-generating systems (see Fig. A 2.08, p. 31). THE SEARCH FOR SIMPLE RULES DESPITE COM- PLEX REQUIREMENTS In practice, the transition to calculating energy demands based on primary nergy is already increasing complexity for practical applications in residential buildings. Prior to this, specifications for maximum permissible heat transfer coefficient values of components or of area-related heating demands were easily comprehensible. In contrast, interpreting primary energy limit values to produce clear recommendations is only possible in the context of on-site energy supply systems and based on experience. The data in the project exam- ples in this book provide actual and practical solu- tions to abstract requirements (see Projects and Experiences, p. 56ff.). Target definitions and energy demand calculations for non-residential buildings are even more complex. According to the first building directive of the EU in 2002 [41], all member states are obligated to adapt their national standardisation and legislation so that electrical energy demands of lighting and air conditioning are also taken into account within mandatory total energy parameters. For the first time, clients and system manufacturers have an in- centive to consider energy efficiency as a decisive developmental aspect in these sectors. Such a pa- rameter system has been in place only in Switzer- land since the beginning of the 1990s: the SIA 380-4 – Electrical Energy in Building Construction directive [42]. Due to the diversity of uses, the total energy parameters for non-residential buildings are differen- tiated to varying degrees according to type. For mixed use, total energy parameters are determined from data for individual building parts, emphasized according to area. Against this background, demonstration projects play an important pioneering role. Beyond calcu- lation results, they offer a basis for defining total energy target values for national standards via operative performance. One excellent example is the Forum Chriesbach research and administrative building, completed in late 2006 in the Swiss munici- pality of Dübendorf and awarded numerous prizes (Figs. A 1.14 and A 1.15, p. 17) [43, 44]. The waste heat recovery from commercial chillers and the output of a 50 m2 tube collector system cover ap- proximately 40% of heating demands. The roughly 12,000 m2 building draws just under 6 kWh/m2 a heat from the district-heating grid. Through an earth-air A 1.12 Necessary reduction in electricity consumption of exist- ing buildings in the United States if corresponding roof- mount photovoltaic systems are to annually balance consumption. A 1.13 The 1.6-MWp photovoltaic systems of the 20,500 m2 “Research Support Center” of the National Renewable Energy Laboratory (NREL) in Golden, Colorado, USA 2011, RNL Design, aim at a zero-energy balance. A 1.14 Energy flow diagram for the heat supply of Forum Chriesbach based on metered values from 2007 (values refer to a heated floor area of 11,170 m2 ) A 1.15 The Aquatic Research Institute of ETH Zurich (Eawag) is located in the Forum Chriesbach office and research building, conceived as a passive house building (MINERGIE-P). Dübendorf, Switzerland 2006, Architect: Bob Gysin + Partner, Energy planner: 3-Plan Haustech- nik AG. A 1.14 A 1.15
- 23. BACKGROUND INFORMATION 18 Lighting Use-specific electricityconsumption Space heating Heat pump Ventilation Cooling Primary energy [kWh/m 2 a] 0 600 500 100 200 300 400 A B C D E F G H I J K L M N O P Q R Institute Production Administration A 1.16 heat exchanger and passive cooling, the build- ing interiors require almost no active cooling. The power demand without central servers is just below 17 kWh/m2 a. In comparison, the output of the 77 kWp photovoltaic system is at 6.4 kWh/m2 a annually. For some building types, comparative studies al- ready provide sufficient results. Primary energy parameters of energy efficient office and adminis- trative buildings in central European climates today are of the order of 80 to 100 kWh/m2 a without appli- ances and equipment. Including equipment, values of 120 to 190 kWh/m2 a are attained during service (Fig. A 1.16) [45, 46], as in approximately half of typical new construction. Individual projects can be even significantly more efficient. Economic com- parisons of demonstration buildings show that their investment costs are no more than 5% above those of comparable buildings, while energy costs com- prise only half the average value [47]. ZERO ENERGY EXTREME: SELF-SUFFICIENT BUILDINGS At first glance, and considering these degrees of energy efficiency, a building that can supply its own energy seems to be just a step away. A self-sufficient building, i.e. a building that isn’t connected to energy infrastructure, guarantees continuous energy supply based on the size of the building’s own, typically solar energy system, and particularly of energy storage devices, without re- verting to other, external resources. Particularly in European climates, the seasonal balance between energy supply and demand requires significant technical investment in energy storage. In climates without pronounced seasonal differences, signifi- cantly simpler concepts are possible. Designs at scales of complex solutions for multiple buildings and for entire residential areas are easier as well. The aim isn’t the sum total of self-sufficient build- ings, but instead the self-sufficiency of the entire complex. The temporal and structural differences in energy demands of individual buildings permit time-related compensation, and thus, reduction of storage volume. SELF-SUFFICIENT HEATING SUPPLY – POSSI- BLE, BUT BETTER NOT ENTIRELY The interior temperature of a solid-construction passive house typically doesn’t fall below 10 °C in central European climate, even without any heating (Figs. A 1.17 and A 1.18) [48]. This temperature is the result of ba- lancing heat gains from the use of solar energy and waste heat generated by individuals and devices with heat losses from transmission and ventilation. Heat storage capacity of building construction en- sures, even during longer phases of absence of use and at lower heat gains, that interior temperatures don’t decline drastically or rise to extremely high interior temperatures when solar gains are high. In A 1.16 Measured primary energy parameters for the demon- stration building of the EnOB development programme (data are standardized according to heated net floor area). For the administrative building, mean primary energy target values are 98 kWh/m2 without and 188 kWh/m2 with use-specific consumption. A 1.17 Adobe construction office building as passive house, Tattendorf, Austria, 2006, Architekturbüro Reinberg A 1.18 Cooling curve for the Tattendorf passive house. In late 2007 and early 2008 the building wasn’t occupied. practice, interior temperatures have upper limits based on user behaviour (window ventilation, sun protection), so that during times of high solar intake unlimited storage charging isn’t possible. Neverthe- less, would it be possible to increase heat storage capacity of necessary structural elements of a build- ing to such a degree that interior temperatures no longer fall below 20 °C solely by passive use of solar energy? PHASE CHANGE MATERIALS Phase change ma- terials (PCM) in the form of micro-encapsulated par- affins can be added to mineral materials of walls and ceilings. Such paraffins (waxes) absorb heat within a defined temperature range, such as from 21 to 22°C during the melting process, and discharge this heat again during solidification. Special salt hydrates have even higher heat storage capacities and are being processed as components e.g. in suspended ceilings. Calculations show, however, that even if all available surfaces in a building were improved in this way or an extremely solid construction type was selected, the resulting storage capacity would in- deed contribute to a further reduction of heating de- mands, but would not make heating systems redun- dant. In summer, in connection with sun screens and nighttime ventilation, more significant effects and even entirely avoiding active cooling systems are possible (see company headquarters in Kemptthal, p. 120ff.). This is primarily because heat is stored
- 24. TOWARDS CLIMATE NEUTRALBUILDINGS 19 19.12. 23.12. 27.12. 31.12. 04.01. 08.01. Temperature [°C] -10 -5 0 5 10 15 20 25 30 Exterior temperature Interior temperature A 1.17 A 1.18 and discharged only in daily cycles. These systems don’t permit buffering of longer heating phases. SOLAR COLLECTORS AND HOT-WATER STORAGE DEVICES In active solar energy use via collectors, a water tank serves as heat storage. As result, the maximum acceptable interior temperature isn’t appli- cable as the upper limit for storage temperature, while the heat insulation of water tanks permits longer storage phases. A simple example, the full heating supply of a 150 m2 house for four occupants, indicates the dimensions required [49]. This system is based on optimally oriented flat tube collectors and a large-volume water storage tank within the building (Figs. A 1.19 and A 1.20, p. 20). If both hot water heating and the entire space heating demands (25 kWh/m2 a) are to be covered by solar energy, then the required col- lector area needs to be at least 30 m2 . Even more importantly, the storage volume needs to be at least 50 m3 . Together with the necessary heat insulation of the storage device, required space equals 5–10% of the building volume. Geometric optimization is, in practice, a very significant factor in determining how much usable space is actually needed. In Europe, the pioneer of self-sufficient system con- cepts was the Jenni house in 1991 in the Swiss mu- nicipality of Oberburg. The 200 m3 house has a col- lector surface area of 84 m2 and a thermal energy storage device holding 118 m3 [50]. The storage device proved much too big. The numerous follow- up projects mainly in Switzerland and Austria oper- ate successfully with significantly smaller systems supplemented by wood furnaces. Advantageously, smaller storage devices also require lower em- bodied energy. Considering the limited number of charge/discharge cycles, this comprises a signifi- cant parameter in the life cycle balancing of large metal storage devices. Large water storage devices made of plastic, however, haven’t proven effective to date in terms of long-term stability, due to occa- sionally high summer storage temperatures. One example for solar heating with high solar frac- tion is the residential system for the Samer Mösl passive house residential complex in the Austrian city of Salzburg (Figs. A 1.22 and M 1.23, p. 21) [51]. The 60 residential units were completed in 2006 by Heimat Österreich (public housing and residential development corporation) as public housing. The climate-neutral heating supply is based on a solar system with 200 m2 flat tube collectors mount on the building’s flat roof and a 21 m3 buffer storage device connected to a 100 kW pellet boiler. The 11 m tall storage tank with a diameter of 1.6 m (measured without insulation) is integrated vertically in the stair- case and extends across all three stories plus the basement. The solar energy system covers approxi- mately half of heating demands. When a system is designed to cover demands to 100% according to a location’s average climate data, experience has shown that, depending on actual weather patterns, energy is sufficient in one year (no additional heating demand). However, in the following year there can be a shortfall [52]. This is primarily due to the sequence of sunny and cloudy days. Long-lasting periods of bad weather or fog are critical. Many successful projects are located in mountain regions that experience more sunny winter days. To omit any service gaps, the required storage volume increases significantly. This effect impacts hot water use first, since higher temperatures are re- quired here than for space heating. In general, heat storage devices for large buildings or residential areas show better results, because the ratio of area loss to storage volume is significantly improved. STORAGE WITH HIGHER HEAT CAPACITY In the- ory, alternatives to large water storage tanks exist with higher storage densities and lower heat losses. If one cubic meter of water is heated or cooled by 30°C, this corresponds to an energy content of 30 kWh. Such a heating process increases the heat energy in a 50 m3 storage tank by only 1500 kWh. In contrast, a suitable phase-change material, such as sodium sulphate, stores approximately 100 kWh/m3 when melting at a temperature of around 30 °C and releases this heat again during solidification. Storage devices with thermo-chemical substances may be
- 25. Another Random Documenton Scribd Without Any Related Topics
- 26. The troops wereunder canvas, and Harry found Fanshawe joint occupant of a tent with a fellow subaltern. "Hullo!" he cried when he saw Harry. "I wondered when I should run up against you. I have heard all about your feat— rescuing beauty and all that. What in the world brought you to this country?" "'Twould be long in the telling. You shall know all in season. I am here on a very special errand. You remember Sherry Minshull?" "As well as I do you. Many's the trout we've caught together. A right good fellow!" "At this moment he is lying under sentence of death in the town-house at Breda. Unknown to me, he had been a soldier, and deserted after thrashing an officer——" "D'ye know him, then?" interposed the other lieutenant. "He is my man." "Oh! Sorry for you both. I had heard about it from an officer of Coy's—Cadogan's, I should say; their name's changed." "Do you know, sir, how he came to be smoked?" "'Twas an Englishman peached—a soldier of fortune, as it appears, who wished to be nameless. He met the men of Cadogan's when they landed at Rotterdam, and arranged a trick by which they got him alone on the open road. 'Twas rather cleverly managed." "And a dirty mean thing to do," said Fanshawe warmly. "Can't something be done for him?" asked Harry. "'Tis hopeless," was Lieutenant Tettefall's reply. "Robins was very vindictive; he painted the man in the blackest colours in his evidence before the court-martial, and not one of the officers of the
- 27. court knew yourman. He has a double offence to answer for; 'tis certain he'll be shot as soon as the forms are completed." Harry's face was then the picture of blank despair. "On my life, 'tis a thousand pities!" said Fanshawe. "I fear there is not the ghost of a chance for him." His face gloomed for a moment; then his high spirits asserted themselves. "But come, Harry, 'tis no good taking on about it; come and forget it over a bottle. I want to hear your story." "No, I'm in no humour for racketing. Would to God I could do something for the poor fellow! Would the colonel intercede if we asked him?" "Not he. He would laugh and crack a joke. If Sherry were a Dutchman, now! The duke is very sweet to the Hollanders at this time, and a word from one of the States might turn him." "General van Santen!" exclaimed Harry. "I had not thought of him. 'Twas he I happened to be of use to, and Sherry did his share too. Yes, 'twould be no harm to try him. Do you know where he is?" "At Lillo," said Tettefall, "full thirty miles away." "I'll ride there. Fanshawe, can you lend me a horse? Mine brought me from the Hague, forty miles and more, and is done up." "I'll lend you mine. I'd like to save Sherry, but 'tis a poor chance. Leave your horse; I'll send him and another to meet you on the way back, in case you have to ride for it." "'Tis good of you. Do you know the road?" "The easiest for you is by Bergen-op-Zoom. You are less likely to be interrupted that way than by the Antwerp road; our forces are camped at Calmpthout on that road, and you might be delayed in
- 28. passing through thelines, to say nothing of falling in with the French beyond." "Thanks and thanks again!" "You'll have to ride hard," added Tettefall. "The duke's at Thielen, twenty miles east of Lillo; and there's no time to lose." "No, I will start at once." "And good luck go with you!" Harry was soon riding at a smart pace along the road to Bergen-op-Zoom, whence he made due south for Lillo, reaching that small fortified place about seven o'clock in the evening. To his intense disappointment he found that General van Santen was at the British head-quarters at Thielen. He had been absent all day, but was expected to return before night. Had it not been so late Harry would have started to meet him on the road, but he did not care to risk missing him. He waited impatiently; the general arrived soon after nine, and when he had heard Harry's story he consented at once to write to Marlborough, mentioning that the bearer of the letter had earned some consideration by his excellent stratagem at Lindendaal, where the condemned man also had done good service. Armed with the letter, Harry set off at ten, hoping to cover the twenty miles to Thielen before the duke had retired to rest. Before starting, General van Santen warned him that parties of French horse were out observing the movements of the confederate army. Finding that he was not familiar with the road, the general sent one of his own orderlies with him, warmly wishing him success. The two riders struck across the fields and by narrow bridle paths almost due east, and passing through one or two ruined villages—among them Eckeren, the scene of the Dutch defeat on
- 29. June 30th—came tothe site of the French camp, vacated and burnt on the approach of Marlborough some ten days before. The air was murky, the sky dark, and Harry was glad of his companion. He was oppressed by the louring prospect of Sherebiah's fate, and the heaviness of the night was not apt to lighten his care. They had ridden for about a third of the distance, and had just left the highway for a cross-road that saved a mile, when all at once, from behind a hedge, there came a sharp challenge in French. "Who goes there?" "A friend," said Harry, and, pulling up, walked his horse slowly forward. "Halt, and give the countersign!" said the voice peremptorily, and dimly, a few yards before him, Harry saw a horseman come into the road. "Now for a dash; keep close!" whispered Harry to the orderly. Setting spurs to his horse, he rode straight at the piquet, hoping that when the inevitable shot was fired it would miss him in the darkness. As the horse sprang forward there was a report and a blinding flash, and a choking sob behind. Harry closed with the Frenchman. There was no time to draw his sword, and he did not wish to raise a further alarm by discharging his pistols. Forcing his horse against the flank of the enemy's, he struck the man with all the weight of his fist, and, taking him by surprise, knocked him from his saddle. He turned to look for his companion; he was prone on the ground, and his startled steed had taken flight. Dismounting in haste, Harry found in a moment that the man was dead, killed by the shot intended for himself. At the same instant he heard a sound of hoofs from behind on his right. Springing on to his horse he set
- 30. him at thegallop across a flat grassy plain, bearing, as nearly as he could judge, due east. Suddenly he heard the thud of more hoofs, still on his right, but this time in front of him. Evidently he was being headed off by another party approaching from the south-east. He swerved to the left, intending to make a detour; as he did so, there was the report of a carbine from behind a hedge a few yards away. He felt his horse quiver, but it galloped on, the man who had fired plunging through the hedge in hot pursuit. Harry's nerves were now at high tension. It was clear that he had stumbled upon a piquet or patrol, or even a more numerous party of the enemy, and the odds were in favour of his meeting the same fate as the poor fellow his guide. Unhappily his horse was beginning to flag. Bending forward to encourage it, and patting its neck, he felt that his hand was covered with blood. The horse had been struck. Harry remembered how it had quivered. The wound accounted for its laboured breathing; it was a good horse, and, not having as yet been seriously pressed, could have held its own with those of the troopers behind. But it was plain to Harry that, with the horse severely wounded, the race must now be short, and the result inevitable. The distance between himself and his pursuers was already lessening; a glance behind showed him four dark figures close upon his heels; a few seconds would decide his fate. At the moment of danger, some men lose their heads, others are braced to the quickest exercise of their faculties. Harry, fortunately for himself, was of the latter class. He saw that to ride on must mean speedy capture; the only chance of escape was to dismount and slip away on foot. But the country here was quite open, he would instantly be seen. He peered anxiously ahead; yes,
- 31. there, against theindigo sky, was a dense mass of black; it was a plantation of some kind; could he but gain that, there was a bare possibility. He dug his spurs into his panting steed, with pity for the poor wounded beast carrying him so gallantly; but he dared not spare it; apart from his own fate, another life hung in the balance. A brief effort was needed; the horse nobly responded, and by the time it reached the edge of the wood had slightly increased the gap between pursuer and pursued. Pulling up suddenly, Harry sprang from the saddle, struck the trembling animal with his scabbard, and as he slipped among the trees heard it dash forward. Being wounded, Harry argued, the horse would certainly slacken its pace when no longer urged by the voice and spur of its rider, and must soon be overtaken. The enemy would immediately guess his device, and if the wood should be of no great extent, they would probably surround it, wait till morning, and capture him at their leisure. He waited breathlessly for the coming of the enemy; he saw them sweep past, bending low in their saddles, two men abreast, like phantom horsemen, so quietly did they ride on the turf. His heart gave a jump when he estimated them as at least half a troop. When they were past he left the wood, and ran across the open plain at right angles to his previous line of flight. As he expected, his manoeuvre was soon discovered. He heard the Frenchmen call to one another; then the thud of returning hoofs on his right, and in a few minutes he saw several dark forms approaching. They were spreading out fanwise. Only the men at the right of the line were directly approaching him at a trot, searching the ground as they rode. The sky was lightening behind them; the
- 32. moon was rising;fortunately, Harry being on foot, the pursuers could not see him so clearly as he saw them. In a moment he perceived that it was a race between him and the man at the end of the line. If he could get beyond the point at which the trooper's present line of march would intersect his own path, he had a reasonable chance of safety. To his dismay he noticed that the man was edging still farther from his comrades, as though suspecting that he was not taking a sufficiently wide sweep. Harry was now panting with his exertions, and in a bath of sweat; he could run no faster over the heavy ground; he felt that the game was up, wondering indeed that the "view halloo!" had not already been given. Plunging blindly, despairingly, on, he was almost at his last gasp when he suddenly fell headlong. He had stumbled into an irrigation ditch. It was overgrown with weeds; in the stress of war the culture of the fields had been neglected; the bottom was dry. The weeds grew high on either side; Harry scrambled on hands and knees into the rank vegetation, and lay still, his flanks heaving, his breath coming and going in quick pants which he felt must be audible yards away. For some seconds he heard nothing but his deep breathing and the thumping of his heart; then the beat beat of hoofs drawing nearer. A horseman passed within a few yards of him, luckily on the right. Another few seconds, and the Frenchman ejaculated an angry "Nom d'un tonnerre!" as his horse struck the ditch and stumbled. He called to his left-hand man, and Harry, cautiously peering through the enveloping weeds, saw him alight and begin to examine the ditch. But he moved away from the fugitive. As soon as he was at a safe distance, Harry, who had by this time recovered his breath,
- 33. crept out andstealthily crawled along the watercourse on hands and knees. For some minutes he continued this arduous progress, rejoicing to hear the men's voices receding moment by moment. Then, judging it safe, he rose and broke into a trot, left the ditch by and by, and continued to pound over fields and paths, through hedges and over ditches, for what seemed to him miles. Then he stopped. All sounds had now ceased save the chirp of crickets, the raucous cry of the corn-crake, and the croak of frogs. He had lost his way; he knew not whether he was near a highway; he was dead tired, his knees trembling under him. But he remembered Sherebiah spending his lonely vigil in the town-house of Breda, waiting for the dawn of his last day, and he set his lips and breathed a vow that the faithful fellow should not die if the last ounce of energy would save him. CHAPTER XIV Harry Rides for a Life The Hour before Dawn—A Trivial Interruption—Recollections—Another Memorandum—The Road to Breda—The Town Clock—Seven Minutes—Against Time—Orange Wins Years afterwards, when Harry was a father and a grandfather, and the children came about his knees clamouring for a story, nothing held them more entranced, nothing caused them such delicious
- 34. creepiness, as hisaccount of the hours that followed his escape from the French. "There was I," he would say, "in the dead of night, a white mist rising from the fields, growing thicker moment by moment—and I knew not where I was, knew not but an unlucky step might bring me again among the enemy. My knees were trembling under me; my mouth was parched; my breast like to burst with the striving of my breath; I was ready to drop and sleep as I fell. But the thought of my faithful servant in that prison; of his being led out and blindfolded, and standing up helpless to be the mark of bullets; of his poor old father that doted on him—ah! my boys, those thoughts were like a goad to me; 'twas as if I was urged on by some unseen power. "I could not now see the stars, so thick was the mist. I could not choose my way. I could but go forward at a venture, praying that my steps might be directed aright. I staggered into slimy ditches; forced my way through quickset hedges, waded weedy streams; once I came full upon a river that I must needs swim. There was never a cottage light to guide me, for though I crossed many a field of corn and flax, many a broad space of pasture land, I came nowhere near a house or farm, and durst not turn aside, feeling as if some strange power bade me go on and on. I know not for how many hours I struggled on thus, taking no count of time; nor did I feel conscious of my great fatigue, but moved on as though I was a soul without body. "It grew darker and darker. The night seemed to press upon me, the mist was like cold clammy hands seizing me to hold me back. Then all at once, going blindly as I did, I well-nigh struck my
- 35. head against alow wall, and was immediately conscious of the smell of tobacco. 'Twas like a breath of heaven to me, boys. I cried aloud, and the echo of my voice seemed that of a startled ghost. A rough voice answered me; I stood still, my heart thumping against my ribs. Footsteps drew near, and I saw the blessed light of a lantern, and in a moment a man had me by the sleeve, and drew back his hand with a cry, for my garments were cold and wet, and the light was flashed in my face, and I saw a big Dutch farmer, who took his pipe from his mouth and bade me tell whence I had come and what was my business. "What I said I know not now, boys, but soon I was wrapped in a cloak, lying upon hay in the bottom of a jolting wain, and my new- found friend driving through the dawn towards Thielen. I fell asleep, and when the farmer's heavy hand stirred me, I was in Thielen, and all around me were soldiers and horses and wagons; 'twas the great duke's camp. The village clock was striking four; the sky was already bright; the camp was astir, for the duke purposed that day to bridge the Nette. "What figure I cut you may imagine. Wet, cold, dishevelled, my face and hands and clothes all bemired, I crawled as best I might from the cart, and staggered to the house where the duke was quartered. There was a sentry at the door: when I said I wished to see the duke he flouted me, laughed in my face, and was for turning me away. But I was in no mood to be delayed. I took from my tunic the sodden letter of General van Santen, and showed it to the fellow, bidding him on peril of his life to stay me. 'Twas enough: he called to a servant; they talked together, eyeing me as though I were some sorry cur: then the man roughly bade me follow him, and within a
- 36. little I stoodin a small chamber, looking with dazed eyes at the man seated at a table there: 'twas my lord Marlborough himself." "A letter from General van Santen, my lord." Marlborough looked up as the servant spoke, but did not straighten himself from his bent position at the table, nor remove his hands from the pair of compasses that were stretched on the map there outspread. Several officers were grouped about him; at a smaller table sat a gentleman dealing with a mass of correspondence. "Mr. Cardonnel," said the duke briefly; then resumed his discussion with the officers. The secretary turned sideways and took the letter. He broke the seal, ran his eye hurriedly over the paper, then laid it on the table. "It shall be looked to," he said, and bent again to his writing. Harry stood for a moment; all his blood seemed to run cold. Then, his whole body a-tingle, he stepped forward. "Pardon me, sir, the matter is most urgent; 'tis a case of life or death. If you would be so good as to lay the letter at once before my lord——" Mr. Cardonnel turned and stared with a sort of scornful wonder at the dishevelled, bedraggled object who addressed him in an English and a cultivated accent. "'Tis too late. My lord's despatch left last night; the man will be shot in a few hours; the matter must e'en take its course." "Sir, may I beg of you——" Harry's voice, unknown to himself, was raised to a tone of passionate entreaty. "My lord——" "What is it, Mr. Cardonnel?" asked Marlborough.
- 37. "General van Santen,my lord, asks the pardon of the deserter Minshull, sentenced by court-martial to be shot. 'Tis too late." "Write and tell the general so, and be done with it." "My lord," broke in Harry, "do but read the general's letter. I have rid and run all night to deliver it; the execution will not yet have taken place, and I know well——" "Who are you, sir?" The duke looked puzzled at the discrepancy between the tone of voice and the disreputable appearance of the youth before him. "My name is Rochester, my lord, the letter—I entreat your lordship to read it—will tell the rest." Marlborough signed to the secretary, received the letter from his hand, and read it quickly. It was not long, and the last paragraph read as follows:— "Perchance, my lord, you may feel that the man's gallantry in the affair at the Comtesse de Vaudrey's may be set against his offence, which though heinous was not unprovoked and is now some years old. If your lordship can reconcile it with the demands of discipline to pardon this unfortunate man, you will I trust find that your clemency is not ill-bestowed." Marlborough fixed his eyes upon Harry. "I understand from this letter that the man is your servant?" He spoke in the low pleasant tone that never varied, whether he addressed peer or peasant. "Yes, my lord, a very true and faithful servant." "And your name is Rochester? Have I not met you before?"
- 38. "Yes, my lord,well-nigh a year ago." "Where?" "At my lord Godolphin's." "At my lord Godolphin's?" A slight ruffle marked his broad white brow. He looked keenly at Harry. All at once his expression changed. "I remember. I had clean forgotten it. You are the young fellow who intervened in my lord's roadside adventure? Ah! and now I bethink me, 'twas your man that did the shouting. The same man?" "Yes, my lord." "That is enough.—Mr. Cardonnel, make out at once an order pardoning the man—what is his name?—and discharging him from the army.—The man whose lungs saved the Lord Treasurer has decidedly a claim to indulgence. But I fear, Mr. Rochester, you are late. These little matters are usually determined by eight o'clock in the morning. It is near five: 'twill be some little time before I can despatch an orderly, and there are fifty odd miles to ride." "With your leave, my lord, I will go myself." "So be it. Mr. Cardonnel will give you the pardon and discharge. It rests with you. I hope you will be in time. Don't spare your horses." "I thank you, my lord, from the bottom of my heart." "There, no more: get to horse. Yet one moment: did I not—I seem to remember it—did I not promise to do something for you?" "'Twas not a promise, my lord." Marlborough smiled, and looked at the boy with approval. "But I intended it as such. I wrote your name, I recollect; papers have a trick of losing themselves: I should have done
- 39. something for youbut for sheer forgetfulness.—Mr. Cardonnel, will you please make a note? Mr.—your full name, sir!" "Henry Winterborne Rochester." "Mr. Henry Winterborne Rochester for an ensigncy.—I had heard of the ruse at the Comtesse de Vaudrey's: naturally I did not connect it with you. You are with Grootz the contractor, I believe?" "I was, my lord, but I have just been commissioned cornet in the Anspach dragoons." Marlborough and the group of officers laughed outright. "Begad, my lord, you're behind the fair," cried Colonel Cadogan, a big burly Irishman of twenty-eight, Marlborough's quartermaster- general. "Ay, indeed, an angel has stirred the pool. But I am delaying you, Mr. Rochester; you must ride hard. Good-bye!" Harry had been itching to get away. Every moment was of importance. Bowing himself out, he hurried to the inn where Fanshawe had promised to stable a horse. It was there ready saddled, in charge of a trooper of Fanshawe's regiment, who said that Harry's own charger Orange was awaiting him half-way to Breda. Harry leapt to the saddle, flung a coin to the man, and in less than two minutes was making his way at a sharp trot among the press of villagers and soldiers thronging the street. Clear of the village he went at a canter through the camp, where all was bustle in preparation for the day's march: then, gaining the free highroad, he set his steed to the gallop. Some minutes later he heard a village clock strike five. Two hours after Harry started on his ride, Godfrey Fanshawe left his tent in company with Lieutenant Tettefall, and mounted his horse
- 40. to ride intoBreda. He had passed a sleepless and anxious night, his mind haunted by the impending fate of Sherebiah, with whom he had spent many a pleasant day on the banks of the Avon, or in the coverts of his father's estate. The execution had been fixed for eight by the clock of the Hervormde Kerk near the market-place, Marlborough's despatch confirming the sentence having arrived late on the previous evening. Fanshawe had seen the major in command, explaining that Harry had gone to see the duke with a view to a remission of the sentence. The major had laughed at the idea, swearing that he would not delay the execution a moment. Galloping into Breda, Fanshawe's first care was to enquire whether Harry had arrived, or whether any message had come from Marlborough countermanding the execution. But nothing had been heard of the one or the other. Fanshawe made a last appeal to the major, but Robins had that officer's ear, and had convinced him that the condemned prisoner was a rascal of whom the army would be well rid. At a quarter after seven the regiment was paraded and marched to the castle park, where the execution was to take place. Fanshawe meanwhile paced moodily up and down, watching the inexorable clock. Suddenly, as he looked at its face for the tenth time, he remembered a legend of the Civil War, which his father had told him: the story of a Royalist trooper who, condemned to die at the ringing of the curfew, had been saved by the heroism of his sweetheart, who climbed the belfry tower, caught the clapper of the bell, and with her delicate hands had prevented the fatal sound. His recollection suggested an idea. There was still forty minutes to spare.
- 41. At the parkgate a knot of idlers had gathered to see the condemned man pass to his doom. Singling out from among these a likely youth, Fanshawe held with him a rapid conversation in whispers; and the two hurried away. They went straight to the sacristan of the Hervormde Kerk, whose cottage was known to the Dutch youth. By the aid of this interpreter Fanshawe explained to the old man that, being much interested in church clocks, he would like to climb the tower and see the mechanism, at the same time slipping a coin into the man's hand. The sacristan was a feeble, tottering old fellow, and was persuaded without difficulty to hand over the key of the tower, on the promise of the English officer to return it within an hour. Armed with the key, Fanshawe then hurried under the boy's guidance to the chief clock-maker's in the town. His shop was not yet open for business, but when he learnt that a clock was in urgent need of attention he agreed to send a young apprentice to oblige the Englishman. At twenty minutes to eight Fanshawe with the young clock-maker ascended the church tower. The boy remained at the door. The clock chimed the three-quarters. "Pray God Harry arrive in time!" was Fanshawe's thought as he returned to the park gate. The clock was too far off for any movement of the hands to be noted. Had it been nearer, a close observer comparing with his own watch might have seen that from this time the long hand of the clock advanced one minute for every two. It still marked ten minutes to eight when Sherebiah, with bound wrists, came up under guard. He smiled serenely when, entering the
- 42. park, he sawFanshawe, whose pale anxious looks betrayed his suffering. "Don't 'ee take on, now, Master Godfrey," he said. "Let 'em aim well and ha' done wi't. Bless 'ee, I bean't afeard. But, Master Godfrey, where be Master Harry? To say good-bye, I mean." "He—he couldn't come, Sherry." "Ah! Well, 'tis no sight for a man o' peace, and he ha'n't donned the breastplate yet. Gi' un my love and respect, an 'ee please, sir; and axe un to remember the old gaffer." Fanshawe gripped his hand, and he passed into the park. "Nay, I won't ha' my eyes tied up," he said to one of the firing squad who approached to bandage him. "Must, must I? Well, I'm not one to go agen the law at the last. Got a clean firelock, mate? Ah! there's the bell a-dingen. Tell Robins— nay, I was gwine to forgive un, but I won't; I'll leave that for Them above." By this time he was standing, with eyes bandaged, against the wall. He ceased to speak; the last stroke of eight had already sounded from several steeples; but the clock of the Hervormde Kerk still wanted seven minutes of the hour. Fanshawe's eyes were riveted on the hands; the soldiers stood at ease, waiting. Meanwhile, what of Harry? The road through Turnhout to Breda passes through a wide moorland region and crosses the river Merk. It was a somewhat heavy road at the best, and the recent passage of troops and baggage wagons had made it rutty and uneven. Harry had started at a stiff gallop; his horse was fresh, and seemed to catch the infection of his eagerness. On he went, scarcely varying his pace, his head
- 43. low, his earsbent back for his rider's encouraging words. At that hour the road was free; Harry met with no obstruction. He dashed through Turnhout, crossed the river to Hoogstraaten, and there found his own black charger awaiting him. He was not quite half-way to Breda. "Orange, my beauty, you must go as you never went before," he cried, as he set the animal at a gallop. The horse pricked his ears in response. He galloped on for mile after mile, scattering dust around him, getting many a stare of wonderment from the peasants at work in the fields. As the miles slipped by, Harry anxiously watched his gallant steed. Great flakes of foam fell from the animal's quivering lips; his nostrils were distended wide; his white eye-sockets were rimmed with red; and still he galloped, panting, striving nobly to respond to the caressing pats and cheering words of his master. "Twenty minutes more, old fellow!" whispered Harry in the beast's ear. "Twenty minutes; if you can only hold out!" He was nearing the end of his ride, but the poor horse was in distress. Spots of blood crimsoned the white foam; Harry fancied that he saw despair in the animal's starting eyes; and when, still a mile on the wrong side of Ginneken, he heard the little church clock strike eight, his heart sank within him. He dared not press the horse further; he might urge it to a short spurt, but the effort would probably be its last; and he had still three miles to go! "Well done, Orange, my beauty!" he cried, patting its ear. "Good horse! Near home now; a few minutes more, old fellow, and then ——" Thus he rode on, inspiriting words on his lips, black despair at his elbow. He knew what military punctuality meant; his ears were
- 44. strained to catchthe sharp rattle of musketry. How far could a volley be heard? He could not pause to speculate on the question; all he could hear was the ringing of his flagging steed's hoofs. He was a mile from Breda. He saw the whole of the little town before him, smoke rising from the chimneys; he overtook a few carts slowly wending towards the market, and heard the wondering exclamations of the wagoners as his blood-flecked steed flashed by. His eyes were straining towards the church tower; pray God the Ginneken clock was fast! But he was too far away to see the hands. On he rode; he came to the open gate; the sentry challenged him, but he was gone before the man had finished the phrase. Now he dug his spurs into the horse's heaving flanks for a last spurt; he clattered through the ill-paved street, shouting to the pedestrians to make way; into the busy little market-place, cumbered with the stalls of apple-women, poulterers, and other purveyors. Boys scurried like rabbits out of his path; women raised shrill cries as stalls were thrown down and apples rolled wide; dogs barked and girls shrieked; but he was past; the church clock said one minute to eight! Out of the market-square, round the corner,—and there was Tettefall, hastening to meet him. "To the park!" cried the lieutenant. Harry shouted in the horse's ear. In half a minute he was in at the park gate, and saw as in a mist the red uniforms of the firing- party, the solitary figure of the condemned man, and the officer in advance of the line with his eyes on the clock. "Saved!" he cried, flinging the duke's order into the air. In a moment he was off the horse, which sank a trembling, heaving heap upon the ground.
- 45. "Just in time—thankGod!" gasped Harry, as he sat with the horse's head between his knees. And upon his dazed ear there fell the first chimes of the beneficent clock, mingled with the loud curt tones of the officer in command as he gave his squad the order to march.
- 46. The Stroke ofEight
- 47. CHAPTER XV The Waterof Affliction The New Cornet—A Visit to Lindendaal—Fanshawe is Presented—The Family Skeleton—Madame Protests—Mademoiselle Insists—Mynheer is Mysterious—A Silent House—The Law Allows It—Not in the Bond—In the Canal—Sherebiah Owns Up By his famous ride from Thielen to Breda Harry became doubly a popular hero. Neither citizens nor soldiers, Dutch or English, felt any particular concern with Sherebiah; but Harry's feat, coming before the memory of his former exploit at Lindendaal had died out, raised him to a pitch of estimation that might well have made him vain, but which in truth he found only embarrassing. Fanshawe, on the other hand, whose ready device with the clock had, as Harry was the first to acknowledge, really been the means of saving Sherebiah, was regarded with cold unfriendliness and even dislike by the townsfolk. To tamper with the town clock they regarded as a monstrous and unpardonable offence, and there was some talk of laying a formal complaint before the Duke of Marlborough. The proposal was warmly debated in the borough council, and the burgomaster had to exercise all his tact to prevent the hotter heads from carrying the day. As for Sherebiah, he was a different man. By his formal discharge from the army the cloud that had pressed upon him for
- 48. nearly nine yearswas dissolved; and now that he had become by official licence, as it were, a man of peace in good earnest, he developed, not merely an unexpected lightness of spirits, but a surprising partiality for the company of soldiers. Every leisure moment he now spent in camp or barrack, retailing endless anecdotes of his former experiences as a man of war, and basing on these a right to criticise and instruct which younger men admitted with humility, to the immense disgust and chagrin of Robins. A few days after the incident, Harry's regiment marched into quarters at Breda, and General van Santen himself paid a flying visit to the town in order to introduce the new cornet to his messmates. Harry was welcomed with open arms, less through the general's sponsorship than through the fame of his own exploits and the proof he had given of courage and daring. One little fact also, which leaked out in course of time, did much to consolidate Harry's reputation as a thoroughly good fellow. He made it his business to find out the relatives of the man who had been killed during the night ride from Lillo. The poor fellow had left a wife and six children, the eldest a boy of sixteen—a slow, earnest, dogged youth who was overcome with shyness when Harry, at the interview with his tearful mother, asked to see him. Harry liked the look of the boy, and offered to apprentice him to an armourer. The mother gladly accepted; and Mynheer Grootz further undertook, at Harry's persuasion, to provide employment for the widow and those of her children who were of age to work. This solicitude of Harry for the family of a man who after all had only been killed by the fortune of war, and had no claim upon him, made an impression on the officers of his regiment; and though it was never mentioned in his presence
- 49. at mess, itdoubtless accounted in large measure for his popularity with officers and men. For some weeks Harry was fully occupied in learning his new duties, practising with sword and rapier, and improving his knowledge of Dutch: Sherebiah's command of the language was of course no longer a mystery. Schomberg's Horse, to which Fanshawe belonged, being likewise quartered outside Breda, Harry often had opportunities of conversation with his friend. Naturally Fanshawe was amazed to hear of the strange enmity of Mr. Berkeley, and shrewdly guessed that the soldier of fortune who had informed on Sherebiah was Captain Aglionby. "And mark my words," he said, "'twas another move against you. Sherry seems to have been a sort of watchdog to you; him out of the way, so much the less difficulty in aiming at you. Though what cause the squire has to wish you ill it passes my wit to divine." "And mine too. 'Tis a desperate revenge on me for being my father's son." "Have a care, Harry. Having gone so far they will not easily be baulked, and in these cut-and-thrust times a blow in the dark, eh?— exit Harry Rochester." "I'll be on my guard, never fear; and I still have Sherry." Harry had not forgotten his friends at Lindendaal. He rode over one free afternoon some three weeks after joining his regiment, and found that the ladies had heard of his promotion, and of his ride, from Mynheer Grootz. Madame de Vaudrey was ecstatic in her congratulations, and only deplored that his new coat was not more brilliant.
- 50. "It suits youwell, mon ami," she said, "but for myself I should like better the red than the blue." "Indeed, Madame," replied Harry with a laugh, "I hadn't given it a thought. There's one advantage in a dull garb: it presents a less conspicuous mark to the enemy." "A point, Monsieur, to which also you had not given a thought till this moment," said Adèle. Harry laughed; then, changing the subject, he added: "Have you heard or seen anything more of Monsieur de Polignac and his friend?" "Nothing, Monsieur Harry," said the comtesse. "And indeed we do not wish to. I only fear lest his silence augurs no good for us. As for his friend, that odious captain——prrrut!" Madame's indignation was too great for articulate expression. The idea of Aglionby daring to pay his addresses to her was too monstrous. As was her wont in this mood, she prattled away about her late husband, Harry listening sympathetically and wondering at the half-smile on Adèle's face. When taking his leave, he said: "An old friend of mine, an English officer, is in camp at Breda. May I bring him, Madame, to call on you one day?" "I shall be charmed, mon cher ami." "Fanshawe speaks little French, I fear, but——" "Ah bah!" interrupted the lady, "that matters nothing at all. Adèle shall teach him." "I shall be charmed, as Mamma says," said Adèle. Harry smiled; nevertheless the suggestion set him thinking as he rode back, and he felt a shade of annoyance when Fanshawe, to whom he mentioned the circumstance, laughed heartily and quoted:
- 51. "'Amo, amas, Ilove a lass'. Is she pretty, Harry? By George! I like the notion." The two rode out together in the following week; Fanshawe made a good impression on Madame de Vaudrey, and his stammering French and good-humoured laughter at his own mistakes appeared to form a bond of union between him and Adèle, for she was soon chatting and smiling with a friendliness and freedom quite different from her reserved attitude towards Harry. Fanshawe talked and laughed gaily all the way back; Harry on the contrary was decidedly glum; and when Sherebiah came to him at night as usual for orders his master's unaccustomed moodiness did not escape him. "What med be the meanen o' this?" he muttered as he went away. "'Yanker didee dudel down Dida dudel launter——' I must ride out-along to Lindendaal one o' these fine days, and putt a question to Katrinka—ay sure." One afternoon in the second week of September Harry, having finished his duties for the day, paid a visit by himself to Madame de Vaudrey. He found the good lady in tears, and Adèle with very pale cheeks and a suspicious redness about her eyes. "Oh, Monsieur Harry!" cried the comtesse as he was shown in, "how glad I am to see you! This is a moment when I need a friend. Look at this letter from that odious Monsieur de Polignac. My poor
- 52. dear husband! Iam glad—it is horrible to say it—but yes, I am glad he did not live to see this terrible day. Read it, cher ami." Harry looked at the letter. It was a curt and formal note from Polignac intimating that, failing compliance with his suit, he was resolved to foreclose his mortgage on the estate one month from the date of the letter, as the terms of the deed provided. He still offered Mademoiselle his hand and heart; did she accept him as a husband he would immediately destroy the mortgage; he gave her a week to decide. "The villain!" ejaculated Harry. "He is within his right, Monsieur," said Adèle. "Right! Legal right, yes; no doubt it is so; but who but a villain would put the matter in this way!" "What I do not understand," said Madame de Vaudrey, "is his motive. If Adèle were a great heiress, I can understand that he should press his suit; but she is not; this poor little estate would not tempt an ambitious man; and as for herself, she has shown her aversion so plainly——" "I hate him!" cried the girl, with a vehemence that surprised Harry, so unlike was it to her usual cold self-contained air. "It is wrong to hate," said her mother; "but the dear girl has no liking for him, and how should a man desire for a wife one to whom he is so indifferent?" "Tell me," said Harry, "is the mortgage for a large sum?" "Alas! yes, for several thousand guilders; that is for the estate alone: the house is separately mortgaged, and the mortgagee in that case is content to receive his interest." "Have you no relatives who would advance the money?"
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