Zero net energy of commercial building

Net Zero Energy Design of Commercial Buildings
A Research Report submitted to the faculty of
San Francisco State University
In partial fulfillment of
The requirements for
The Degree
Master of Science
In
Engineering: Energy Systems
By
Ruchir Hemant Shah
San Francisco, California
December 2015

i
Copyright by
Ruchir Hemant Shah
2015

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CERTIFICATION OF APPROVAL
I certify that I have read Net Energy Design of Commercial Buildings by Ruchir H. Shah, and
that in my opinion this work meets the criteria for approving a research project report submitted
in partial fulfillment of the requirement for the degree Master of Science in Energy Systems at
San Francisco State University.
Ahmad Ganji, Ph.D.
Professor
A. S. (Ed) Cheng, Ph.D.
Professor

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Net Zero Energy Design of Commercial Buildings
Ruchir Hemant Shah
San Francisco, California
2015
The vision of Net Zero Energy Buildings (NZEBs) is compelling. In theory, the amount of
energy consumed by the building for an entire year should be less than or equal to the amount of
energy produced by the onsite renewable source.
The main aim of my project is to build maximum number of floors in the building and make it
zero net site energy using roof-top solar photovoltaic (PV) panels. To check weather effect,
project is simulated in three different weather conditions.
Results obtained from the simulation in this project under the three weather conditions show that
a maximum of two floors can be designed in new energy efficient buildings to make them zero
net site energy using roof mounted solar PV. The simulation results indicate that only one floor
can be built as a net zero source energy building if natural gas consumption converted into
electrical energy consumption. To design more than two floors in new construction or to design
more than one floor in existing building to make net zero energy, we need to use building site for
energy production, in addition to the roof-top.
Analysis methods for design and implementation of NZEBs are also discussed. The discussion is
followed by several ways to achieve large-scale, replicable NZEBs performance. Various passive
and renewable energy strategies are implemented, including full daylighting, high-performance
lighting, natural ventilation, infiltration and thermal mass. Ground source heat pumps have been
used for space conditioning as well domestic water heating.
I certify that the Abstract is a correct representation of the content of this thesis.
Chair, Project Committee Date

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PREFACE AND/OR ACKNOWLEDGEMENTS
I want to thank Professor Ahmad Ganji for his immense support and guidance in the
accomplishment of my project. I would like to thank him further for meeting with me every
week and helping me solve all the doubts and providing detailed solutions. This helped me
developed a lot of insights on NZE and gain conceptual knowledge during the span of this
project. Professor Ganji was extremely helpful and generous throughout the project
development.
I would also like to thank Professor A.S Cheng to be my other committee chair professor for his
assistance. I truly thank professor Cheng to support me during my entire stay at San Francisco
State University.

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TABLE OF CONTENTS
Table of Contents………………………………………………………………………………...V
List of Figures………………………………………………………………………………….VII
List of Tables………………………………………………………………………………….VIII
1. Introduction……………………………………………………………………………………1
1.1. Problem Definition……………………………………………………………………….1
1.2. Project Scope………………………………………………………………………..........1
2. Climate Assessment…………………………………………………………………………....2
3. Energy Efficient Buildings………………………………………………………………….....3
3.1. Passive Design…………………………………………………………………………….4
3.2. Building Envelop………………………………………………………………………….8
3.3. Mechanical Systems………………………………………………………………………10
3.3.1. Traditional System…………………………………………………………………11
3.3.2. Heat Pumps………………………………………………………………………...11
3.4. Domestic Hot Water……………………………………………………………………...16
3.5. Lighting…………………………………………………………………………………..17
4. Renewable Energy…………………………………………………………………………….19
4.1. Solar Electric Generation…………………………………………………………………19
4.2. Solar Water Heating………………………………………………………………………20
5. Plug Loads and Occupancy……………………………………………………………………21
6. Modeling Simulation …………………………………………………………………………22
6.1 Building Specification…………………………………………………………………….22
6.2 Modeling Tool…………………………………………………………………………….23

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6.3 Model Specification……………………………………………………………………….24
6.4. Modeling Results…………………………………………………………………………27
7. Simulation Verification………………………………………………………………………..34
8. Future of Net Zero Energy Building………………………………………………………......35
9. References……………………………………………………………………………………..36

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LIST OF FIGURES
Figures Page
1. Night Purge Ventilation………………………………………………………5
2. Daylighting…………………………………………………………………... 7
3. Natural Ventilation…………………………………………………………... 8
4. Horizontal Closed loop Ground Source Heat pump System………………… 9
5. Vertical Closed loop Ground Source Heat pump System…………………….13
6. Pond/Lake Closed loop Ground Source Heat pump System………………….14
7. Open Loop Ground Source Heat Pump……………………………………… 15
8. Window Technology………………………………………………………….16
9. Commercial Building Use Breakdown……………………………………….21
10. Building Schematic…………………………………………………………..22

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LIST OF TABLES
Table 6-1 Tabular inputs used in eQuest for baseline building, Energy Efficient
techniques and Net Zero Energy for different location………………………...24
Table 6-2 Output of new office building with 50,000 Sqft in Phoenix, AZ for different
floors…………………………………………………………………………….28
Table 6-3 Output of new office building with 100,000 Sqft in Phoenix, AZ for different
floors…………………………………………………………………………….28
Table 6-4 Output of new office building with 50,000 Sqft in San Jose, CA for different
floors…………………………………………………………………………….28
Table 6-5 Output of new office building with 100,000 Sqft in San Jose, CA for different
floors…………………………………………………………………………….28
Table 6-6 Output of new office building with 50,000 Sqft in Chicago, IL for different
floors…………………………………………………………………………….29
Table 6-7 Output of new office building with 100,000 Sqft in Chicago, IL for different
floors…………………………………………………………………………….29
Table 6-8 Output of conventional office building with 100,000 Sqft in San Jose, CA for
different floors…………………………………………………………………..30
Table 6-9 Output of conventional office building with 100,000 Sqft in Phoenix, AZ for
different floors……………………………………………………………………30
Table 6-10 Output of conventional office building with 100,000 Sqft in Chicago, IL for
different floors…………………………………………………………………...31
Table 6-11 Comparison between new and existing building parameters for Phoenix, AZ with
Table 6-12 Comparison between new and existing building parameters for San Jose, CA with
Table 6-13 Comparison between new and existing building parameters for Chicago, IL with
Table 6-14 Comparison between RSF building real data and my simulation output………...35

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1. Introduction
Buildings have a significant impact on energy use and the environment. Commercial and
residential buildings use almost 40% of the primary energy in the United State (EIA 2005). The
energy used by the building sector continues to increase, primarily because new buildings are
constructed faster than existing ones are retired. Electricity consumption in the commercial
building sector doubled between 1980 and 2000 and is expected to increase another 50% by
2025 (EIA 2005). To address the growing energy use in the commercial building sector, an
influential community of industry leaders and researchers has committed to pushing the
boundaries of building performance to develop net-zero energy buildings (NZEBs).
Big bold goals adopted by California Public Utilities Commission (CPUC) in 2007-08 was, all
new residential construction in California will be zero net energy by 2020. All new commercial
construction in California will be zero net energy by 2030 (CPUC 2008).
1.1 Problem Definition
At its core, the amount of energy consumed by building for entire year should be less than or
equal to amount of energy produce by onsite renewable energy sources. The National Renewable
Energy Laboratory (NREL) has defined four ways of measuring and defining net zero energy for
buildings; net zero site energy, net zero source energy, net zero energy emissions, net zero
energy cost.
Net Zero Site Energy building produces at least as much renewable energy as it uses over the
course of the year when accounted for the site (Torcellini 2006)
Net Zero Source Energy building produces or purchases at least as much renewable energy as it
uses over the course of a year when accounted for at the energy source (Torcellini 2006).
Net Zero Energy Emission building produces or purchases enough emission-free renewable
energy to offset emissions from all energy used in the building over the course of a year
(Torcellini 2006).
Net Zero Cost Building receives at least as much financial credit for exported renewable energy
as it is charged for energy and energy services by the utility over the course of the year
(Torcellini 2006).
From the above definitions, the modeling simulation in this report is based on net zero site
energy using roof mounted solar PV.
1.2 Project Scope
The project is carried out to determine how many floors can be built in an energy efficient
commercial building to make it a net zero site energy building with roof-top PV system as the
energy source. The results are verified in different climates for all the buildings compliant with
current standards. Two office buildings are taken into consideration each having 50,000 Sqft and
100,000 Sqft areas with maximum number of floors viable. The modelling is carried out in given

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climatic conditions for the cities of San Jose, CA, Chicago, IL and Phoenix, AZ. The modeling
simulation is developed using a ground source heat pump for heating and cooling source .Several
passive architecture energy efficient techniques such as daylighting, energy efficient building
envelope, lighting controls and natural ventilation are applied. In modeling of conventional
buildings, CA Title 24 and ASHRAE 90.1 standards are utilized to check net zero energy
possibilities. The results are compared with a new building to show the effects of energy efficient
techniques.
2. Climate Assessment
Climate is critical variable in the design of a net zero energy project. It influences external
thermal loads of a project and it is also a free source of energy. Simply we can say that net zero
energy project must be climate responsive. Climate classes are:
A. Tropical
B. Arid
C. Temperate
D. Cold
E. Polar
A. Tropical
Tropical climates are characterized by yearlong hot and moist weather with rainfall and
humidity. Example location: Miami, FL
Design Response:
• Reduce cooling load with passive strategies, such as minimizing solar radiation, reduce
thermal conduction, reducing internal heat gain.
• Daylight lowers lighting load and internal heat gain. Natural Ventilation is useful for
some tropical climates.
• Light colors for exterior surface will reflect rather than absorbs solar radiation.
B. Arid
Characterized by lack of precipitation. Can be hot or cold. Example locations: Nevada, Arizona,
New Mexico.
Design response:
• Hot climates are cooling dominated and cold climates are heating dominated.
• Night purge ventilation can also be effective for moderate cooling.
• Provide natural ventilation and solar shading during cooling season.

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C. Temperate
Characterized by warm summer and cool winter. Example location: California
Design response:
• Night purge ventilation can also be effective for moderate cooling.
D. Cold
Characterized by cold winter with snow. Example location: Rochester, NY
Design response:
• Reduce heat transfer through conduction with well insulated building envelop
E. Polar
Extremely cold weather often with no summer season and typically treeless. No Human
population. Example location: Arctic
The simulation is performed for Phoenix, AZ as arid, San Jose, CA as temperate and Chicago, IL
as cool and humid.
3. Energy Efficient Buildings
Energy efficient buildings are the ones that use a minimum amount of energy throughout the
year. To achieve energy efficiency, passive and active architecture strategies play vital roles.
Passive architecture includes, daylighting, natural ventilation, air tightness of the building, and
efficient building envelopes. Active architecture contains mechanical systems in the building like
Heating Ventilation Air Conditioning (HVAC) and Domestic Hot Water (DHW). This section
will provide a brief introduction of passive and active architectures, lighting systems in the
building and their roles in energy efficient buildings.
3.1 Passive Design
Passive design is defined as the use of architecture and climate to provide heating, cooling,
ventilation and lighting. In other words technique which does not require any active systems. It is
one of the most important parameters to a get free source of energy in net zero energy building
for heating and cooling. However, we cannot rely totally on passive design to provide heating

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and cooling so we still need active systems in the building, but the main aim is to minimize the
use of active system’s usage (Hootman 2012).
Passive Strategies Types
This section includes different passive strategy types like, thermal mass, night purge, super
insulation, air tightness, daylighting, and daylighting.
Thermal Mass: In building design, thermal mass is a property of the mass of a building which
enables it to store heat, providing "inertia" against temperature fluctuations. Thermal mass will
absorb thermal energy when the surroundings are higher in temperature than the mass, and give
thermal energy back when the surroundings are cooler, without reaching thermal equilibrium.
Ideal materials for thermal mass are those materials that have:
• High specific heat capacity,
• High density
Any solid, liquid, or gas that has mass will have some thermal mass. A common misconception
is that only concrete or earth soil has thermal mass; even air has thermal mass (Hootman 2012).
Night Purge: Night-Purge Ventilation (or "night flushing") keeps windows and other passive
ventilation openings closed during the day, but open at night to flush warm air out of the building
and cool thermal mass for the next day. Night-purge ventilation is useful when daytime air
temperatures are so high that bringing unconditioned air into the building would not cool people
down, but where night time air is cool or cold. This strategy can provide passive ventilation in
weather that might normally be considered too hot for it (Hootman 2012). Night flushing works
by opening up pathways for wind ventilation and stack ventilation throughout the night, to cool
down the thermal mass in a building by convection. Early in the morning, the building is closed
and kept sealed throughout the day to prevent warm outside air from entering. During the day,
the cool mass absorbs heat from occupants and other internal loads. This is done largely by
radiation, but convection and conduction also play roles (Hootman 2012). Figure 1 will give
more idea about night purge ventilation.

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Figure 1. Night Purge Ventilation
Superinsulation: Superinsulation is an approach to building design, construction, and
retrofitting that dramatically reduces heat loss (and gain) by using much higher levels of
insulation and air tightness than normal. Superinsulation is one of the ancestors of the passive
house approach (Hootman 2012).
It is possible and increasingly desirable, to retrofit superinsulation to existing houses or
buildings. The easiest way is often to add layers of continuous rigid exterior insulation and
sometimes by building new exterior walls that allow more space for insulation. A vapor
barrier can be installed on the outside of the original framing but may not be needed. An
improved continuous air barrier is almost always worth adding, as conventional homes tend to be
leaky, and such an air barrier can be important for energy savings and durability (Hootman
2012).
Air Tightness: can be defined as the resistance to inward or outward air leakage through
unintentional leakage points or areas in the building envelope. This air leakage is driven by

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differential pressures across the building envelope due to the combined effects of the stack,
external wind and mechanical ventilation systems.
Air tightness is the fundamental building property that impacts infiltration. An airtight building
has several positive impacts when combined with an appropriate ventilation system (whether
natural, mechanical, or hybrid) (Hootman 2012).
Daylighting: Daylighting is the controlled admission of direct and diffuse Sunlight into a
building to reduce electric lighting and saving energy. A key feature of energy efficient
commercial building design is maximizing the use of natural daylight to supplant electric
lighting in interior spaces. Natural light entering through windows and skylights is not only free,
but can also provide occupants with a feeling of connection to the outdoors. Moreover, when
properly designed to minimize direct beam penetration, the use of natural daylight provides the
most light for the least amount of internal heat gain an important quality given that even in
northern climates mechanical cooling of interior spaces is often needed for much of the year. The
dynamism of daylight provides visual and thermal comfort, but is also central to the regulation of
human circadian rhythms. Daylight enhances our mood and focus, improves immune system
function, and can even suppress drowsiness (Hootman 2012). Figure 2 will show office room
with daylighting.

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Figure 2. Daylighting
Natural Ventilation: Natural ventilation is the process of supplying air to and removing air from
an indoor space without using mechanical systems. It refers to the flow of external air to an
indoor space as a result of pressure differences arising from natural forces. There are two types
of natural ventilation occurring in buildings: wind driven ventilation and buoyancy-driven
ventilation. Wind driven ventilation arises from the different pressures created by wind around a
building or structure, and openings being formed at the perimeter which then permit flow
through the building. Buoyancy-driven ventilation occurs as a result of the directional buoyancy
force that results from temperature differences between the interior and exterior. Since the
internal heat gains which create temperature differences between the interior and exterior are
created by natural processes including the heat from people, and wind effects are variable,
naturally ventilated buildings are sometimes called "breathing buildings" (Hootman 2012).
Figure 3 will give more idea about building with natural ventilation.

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Figure 3. Natural Ventilation
3.2 Building Envelop
Building envelop plays a massive role in the implementation of passive strategies, and so should
be integrated with mechanical and electrical design. The building envelop is a critical element in
the energy performance of any building, but it is absolutely vital for the performance of net zero
buildings. This section will describe important element involved in building envelop and their
effects in energy performance.
Walls: Energy efficient walls are built to minimize heat transfer. The R value, the measure of a
material’s ability to stop the flow of heat is used to compare building material. The higher the R
value greater the material will protect against energy loss. The total R value of wall takes into
consideration all products from which wall is made. Insulation also plays an important role for
energy efficient building.
Thermally massive material have high density and a high specific heat capacity. Material such
as, concrete, stone, masonry and water have the capability to store heat and release heat back into
the environment once the ambient temperature cools. One of the primary benefits of thermal
mass is its capability to even out temperature swings in the interior environment. Thermal mass

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can also be used on the exterior envelop in the hot climate as a means of showing down
temperature swings through the envelope (Hootman 2012).
Windows: When selecting windows for energy efficiency, it's important to first consider
their energy performance ratings in relation to climate and building design. A window's energy
efficiency is dependent upon all of its components. Frames conduct heat, contributing to a
window's overall energy efficiency, particularly its U-factor. Glazing or glass technologies have
become very sophisticated, and designers often specify different types of glazing or glass for
different windows, based on orientation, climate and building design (Haglund 2012). Figure 4
will give details of energy efficient window technology.
Figure 4 Window Technology
Another important consideration is how the windows operate, because some operating types
have lower air leakage rates than others, which will improve energy efficiency.

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Single glazing is a very poor insulator, with an R-value of about 1 (equivalent to U-1). Increasing
the number of panes in a window improves the insulating value of the window, so clear double
glazing has an R-value of about 2 (equivalent to U-0.5), and clear triple glazing has an R-value
of about 3 (equivalent to U-0.33). The values for double or triple glazing can be further improved
by including one or two low-e coatings and an inert gas fill between the panes. The best double-
glazed windows have a whole-window U-factor of about 0.27, while the best triple-glazed
windows which are used in present simulation have a whole-window U-factor of about 0.17
(Haglund 2012).
Infiltration: Infiltration is the unintentional or accidental introduction of outside air into a
building, typically through cracks in the building envelope and through use of doors for passage.
Infiltration is sometimes called air leakage. The leakage of room air out of a building,
intentionally or not, is called exfiltration. Infiltration is caused by wind, negative pressurization
of the building, and by air buoyancy forces known commonly as the stack effect (Athienitis
2006).
Because infiltration is uncontrolled, and admits unconditioned air, it is generally considered
undesirable except for ventilation air purposes. Typically, infiltration is minimized to reduce
dust, to increase thermal comfort, and to decrease energy consumption. For all buildings,
infiltration can be reduced via sealing cracks in a building's envelope, and for new construction
or major renovations, by installing continuous air retarders. In buildings where forced ventilation
is provided, their HVAC designers typically choose to slightly pressurize the buildings by
admitting more outside air than exhausting so that infiltration is dramatically reduced (Athienitis
2006).
Reduced air infiltration combined with proper ventilation cannot only reduce energy bills, but it
can also improve the quality of indoor air. Outdoor air that leaks indoor makes it difficult to
maintain comfort and energy efficiency. As per Department of Energy (DOE) air leakage
accounts for 25–40% of the energy used for heating and cooling in a typical building (Athienitis
2006).
3.3 Mechanical Systems
The design of energy efficient building systems or mechanical systems for a net zero energy
project is depends upon the passive architecture of the building. For most commercial building
types, we cannot expect climate responsive architecture with passive strategies to meet all the
desired interior function of the light, comfort, air quality and hot water all the time. Mechanical
systems required to provide these functions when passive strategies alone are insufficient
(Collyer 2012). This section includes a brief discussion of mechanical systems in conventional
and new construction buildings.

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3.3.1 Conventional Mechanical Systems
For heating in conventional buildings boilers are used to generate steam or hot water and can be
fired by natural gas, fuel oil, or coal. Their combustion efficiencies varies from 78% to 86%.
Furnaces can be used for residential and small commercial heating systems. Furnaces use natural
gas, fuel oil, and electricity for the heat source. Natural gas furnaces are available in condensing
and non-condensing models (Graham 2014).
In large commercial and institutional buildings, devices used to produce cool water are called
chillers. The water is pumped to air handling units to cool the air. They use either mechanical
refrigeration processes or absorption processes. Mechanical refrigeration chillers may have one
or more compressors. These compressors can be powered by electric motors, fossil fuel engines,
or turbines. Absorption chillers are heat-operated devices that produce chilled water via an
absorption cycle. Absorption chillers can be direct-fired, using natural gas or fuel oil, or indirect-
fired. Large and medium-sized air-cooled electric chillers have 0.95-0.85 kW/ton (COP of 3.7 to
4.1) (Graham 2014).
3.3.2 Heat Pumps
For climates with moderate heating and cooling needs, heat pumps offer an energy-efficient
alternative to furnaces and air conditioners. Like refrigerators, heat pumps use electricity to
move heat from a cool space to a warm space, making the cool space cooler and the warm space
warmer. During the heating season, heat pumps move heat from the cooler outdoors into the
warmer environment and during the cooling season, heat pumps move heat from cooler
environment into the warm outdoors. Because they move heat rather than generate heat, heat
pumps can provide equivalent space conditioning at as little as one quarter of the cost of
operating conventional heating or cooling appliances (Energy 2008). Classifications and
operations of heat pumps are described in the following sections.
Air Source Heat Pumps
An air-source heat pump can provide efficient heating and cooling for the home. When properly
installed, an air-source heat pump can deliver one-and-a-half to three times more heat energy to a
home than the electrical energy it consumes. This is possible because a heat pump moves heat
rather than converting it from a fuel like combustion heating systems do (Energy 2008).
Air-source heat pumps have been used for many years in nearly all parts of the United States, but
until recently they have not been used in areas that experienced extended periods of subfreezing
temperatures. However, in recent years, air-source heat pump technology has advanced so that it
now offers a real space heating alternative in colder regions (Energy 2008).

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Ground Source Heat Pump
Geothermal heat pumps (GSHPs), sometimes referred to as GeoExchange, earth-coupled,
ground-source, or water-source heat pumps, have been in use since the late 1940s. They use the
constant temperature of the earth as the exchange medium instead of the outside air temperature.
This allows the system to reach fairly high Coefficient of Performance (COP) on the coldest
winter nights, compared to air-source heat pumps on cool days (Energy 2008).
Although many parts of the country experience seasonal temperature extremes -- from burning
heat in the summer to sub-zero cold in the winter. A few feet below the earth's surface the
ground remains at a relatively constant temperature. Depending on latitude, ground temperatures
range from 45°F (7°C) to 75°F (21°C). Like a cave, this ground temperature is warmer than the
air above it during the winter and cooler than the air in the summer. The GSHPs takes advantage
of this by exchanging heat with the earth through a ground heat exchanger (Energy 2008).
As with any heat pump, geothermal and water-source heat pumps are able to heat, cool, and, if so
equipped, supply the building with hot water. Relative to air-source heat pumps, they are quieter,
last longer, need little maintenance, and do not depend on the temperature of the outside air
(Energy 2008).
A dual-source heat pump combines an air-source heat pump with a geothermal heat pump. These
appliances combine the best of both systems. Dual-source heat pumps have higher COP than air-
source units, but are not as efficient as geothermal units. The main advantage of dual-source
systems is that they cost much less to install than a single geothermal unit, and work almost as
well (Energy 2008).
Even though the installation price of a geothermal system can be several times that of an air-
source system of the same heating and cooling capacity, the additional costs are returned as
energy savings in 5 to 10 years. System life is estimated at 25 years for the inside components
and 50+ years for the ground loop. There are approximately 50,000 geothermal heat pumps
installed in the United States each year (Energy 2008).
There are four basic types of ground loop systems. Three of these -- horizontal, vertical, and
pond/lake -- are closed-loop systems. The fourth type of system is the open-loop option. Which
one of these is best depends on the climate, soil conditions, available land, and local installation
costs at the site (Energy 2008). During a given modeling simulation project, closed loop vertical
system is used. All of these approaches can be used for residential and commercial building
applications.

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Ground Loop
Most closed-loop geothermal heat pumps circulate an antifreeze solution through a closed loop
usually made of plastic tubing that is buried in the ground or submerged in water. A heat
exchanger transfers heat between the refrigerant in the heat pump and the antifreeze solution in
the closed loop. The loop can be in a horizontal, vertical, or pond/lake configuration (Energy
2008).
One variant of this approach, called direct exchange, does not use a heat exchanger and instead
pumps the refrigerant through copper tubing that is buried in the ground in a horizontal or
vertical configuration. Direct exchange systems require a larger compressor and work best in
moist soils (sometimes requiring additional irrigation to keep the soil moist), should avoid
installing in soils corrosive to the copper tubing. Because these systems circulate refrigerant
through the ground, local environmental regulations may prohibit their use in some locations
(Energy 2008).
Horizontal Ground Loop
This type of installation is generally more cost-effective for residential installations, particularly
for new construction where sufficient land is available. It requires drains at least four feet deep.
The most common layouts either use two pipes, one buried at six feet, and the other at four feet,
or two pipes placed side-by-side at five feet in the ground in a two-foot wide trench (Energy
2008). Figure 5 will show closed loop horizontal system arrangements.
Figure 5. Horizontal Closed loop Ground Source Heat pump System

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Vertical Ground Loop
Large commercial buildings and schools often use vertical systems because the land area
required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is
too shallow for trenching, and they minimize the disturbance to existing landscaping. For a
vertical system, holes (approximately four inches in diameter) are drilled about 20 feet apart and
100 to 400 feet deep. Into these holes go two pipes that are connected at the bottom with a U-
bend to form a loop. The vertical loops are connected with horizontal pipe (i.e., manifold),
placed in trenches, and connected to the heat pump in the building (Energy 2008). Figure 6 will
show vertical closed loop system arrangements.
Figure 6. Vertical Closed loop Ground Source Heat pump System
Pond/Lake Loop
If the site has a sufficient water body, this may be the lowest cost option. A supply line pipe is
run underground from the building to the water and coiled into circles at least eight feet under
the surface to prevent freezing. The coils should only be placed in a water source that meets
minimum volume, depth, and quality criteria (Energy 2008). Figure 7 will show closed loop
pond/lake arrangements.

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Figure 7. Pond/Lake Closed loop Ground Source Heat pump System
Open loop Systems
This type of system uses well or surface body water as the heat exchange fluid that circulates
directly through the ground heat pump system. Once it has circulated through the system, the
water returns to the ground through the well, a recharge well, or surface discharge. This option is
obviously practical only where there is an adequate supply of relatively clean water, and all local
codes and regulations regarding groundwater discharge are met (Energy 2008). Figure 8 will
show open loop system arrangements.

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Figure 8. Open Loop Ground Source Heat Pump
Hybrid Systems
Hybrid systems using several geothermal resources, or a combination of a geothermal resource
with outdoor air (i.e., a cooling tower), are another technology option. Hybrid approaches are
particularly effective where cooling needs are significantly larger than heating needs. Where
local geology permits, the "standing column well" is another option. In this variation of an open-
loop system, one or more deep vertical wells are drilled. Water is drawn from the bottom of a
standing column and returned to the top. During periods of peak heating and cooling, the system
can bleed a portion of the return water rather than re-injecting it all, causing water inflow to the
column from the surrounding aquifer. The bleed cycle cools the column during heat rejection,
heats it during heat extraction, and reduces the required bore depth (Energy 2008).
3.4 Domestic Hot Water
In conventional commercial buildings hot water is used for space heating and domestic hot
water, and energy consumption for heating the water in commercial building is less as compare
to other facilities like hotels, restaurants. Here ground source heat pump is used to heat water
used for space heating and for domestic hot water.

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Low Energy Hot Water:
The following ideas can save energy used to produce hot water (Hootman 2012).
Minimize water consumption is the best approach to reducing energy use. Installing low flow hot
water fixtures and appliances is good way to reduce the amount of water consumption (Hootman
2012).
Using Heat pump instead of boilers or electric heater. As per research heat pump are more
efficient than boilers and electric heater (Hootman 2012).
In domestic hot water, placing the heater close to the sink by using point of use water heater
(Hootman 2012).
Using a hot water recirculation loop with a close connection of the point of use (Hootman 2012).
Grouping hot water fixtures close to heater locations (Hootman 2012).
3.5 Lighting Systems
Lighting power density (LPD) limits are a major part of all current building energy codes. LPD
sets maximum limit for the installed power over a specified area which is expressed in Watts per
Square Foot (W/ft2). The LPD limit values found in energy codes are typically based on a space-
type lighting model systems consisting currently available lighting product characteristics, light
loss factors, building construction data, and professional design experience. These factors are
used to calculate appropriate values for each building space type (Codes 2012). This Section
includes description of indoor and outdoor lighting controls.
Indoor Lighting Control
Interior lighting is one of the largest electricity energy end-uses in many commercial buildings
and controls can have a significant effect on their energy use. Interior lighting controls give
occupants control over the electric lighting in a space, and can be used to manage building
lighting automatically. Effectively controlling the space lighting results not only in occupant
comfort, but also in energy savings. Efficient lamps and light fixtures reduce the total installed
lighting power whereas controls generally reduce the amount of lighting used or the amount of
time for which lighting is used. Lighting controls can be classified as those required across the
entire building and those that must be applied space by space (Codes 2012).

18
Manual Control
The basic control provided in all spaces is a wall switch that allows occupants to turn general
lighting on and off. This manual control device must be easily accessible and must be located
such that the lights it controls are seen easily from the control location. Manual controls provide
a minimum level of comfort for occupants. Manual control is not required in spaces such as
corridors, stairwells, or other spaces where turning the lights off would be damaging for entry
and security (Codes 2012).
Under ASHRAE Standard 90.1, for spaces smaller than 10,000 Sqft, one manual control device
is required for every 2,500 Sqft. For spaces larger than 10,000 Sqft, one manual control device is
required for every 10,000 Sqft (Codes 2012).
Automatic Shutoff Control
On/off controls and lighting reduction controls are manual controls that are needed in most
spaces. However, these controls rely on occupants to obtain energy savings. There is no
guarantee that these controls will save energy. When occupants are not present in a space and
during the night, there is ample opportunity to turn lights off. Automatic lighting controls are
required to control the lighting during these unoccupied periods. Automatic controls also
guarantee energy savings from lighting (Codes 2012).
Energy codes require that all building spaces be controlled by an automatic control device that
shuts off general lighting. This control device must turn off lights in response to a time-based
operation schedule, occupancy sensors that detect the absence of the occupants, or a signal from
the building’s energy management system or some other system that indicates that the space is
empty (Codes 2012).
In ASHRAE Standard 90.1, the occupant must be able to reduce the lighting power to between
30% and 70% of full power using the manual control device. The International Energy
Conservation Code (IECC) requires this stepped reduction to be lower than or equal to 50% of
full power. Spaces such as corridors, stairways, electrical/mechanical rooms, public lobbies,
restrooms, storage rooms, and sleeping units are exempted. Also exempted are spaces with only
one luminaire with a rated power of less than 100 W and spaces with an LPD allowance of less
than 0.6 W/ft2. The IECC exempts areas within spaces that are controlled either by an occupancy
sensor or by daylighting controls (Codes 2012).
Exterior lighting control
The following controls are required by ASHRAE Standard 90.1.
• Building façade and landscape lighting is required to be shut off between midnight or
business closing, whichever is later, and 6 a.m. or business opening, whichever is earlier.
The façade and landscape lighting at this building must be turned off from 2 a.m. through
6 a.m. (Codes 2012)

19
• All other lighting must be reduced by at least 30% of full power using either occupancy
sensors to turn lights off within 15 minutes of sensing zero occupancy, or from midnight
or one hour from close of business, whichever is later, until 6 a.m. or business opening,
whichever is earlier (Codes 2012).
4. Renewable Energy
Renewable energy is generally defined as energy that comes from resources which are naturally
replenished on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal
heat. Renewable energy replaces conventional fuels in four distinct areas: electricity generation,
air and water heating/cooling, motor fuels, and rural (off-grid) energy services. To that end, this
topic provides general guidance on planning renewable energy systems for net zero energy
buildings, with focus on early planning and concepts needed to achieve effective integration into
a net zero energy building (Hootman 2012). This topic heavily leans on solar electricity from
photovoltaic systems as an important source of renewable energy for net zero energy buildings
and brief discussion on solar water heating.
4.1 Solar Electric Generation
Solar power is the conversion of sunlight into electricity, either directly using photovoltaics
(PV), or indirectly using Concentrated Solar Power (CSP). Concentrated solar power systems use
lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam.
Photovoltaics convert light into an electric current using the photovoltaic effect (Hootman 2012).
A photovoltaic or PV system, is a powerful system designed to supply usable solar power by
means of photovoltaics. It consists of an arrangement of several components, including solar
panels to absorb and convert sunlight into electricity, a solar inverter to change the electric
current from DC to AC, as well as mounting, cabling and other electrical accessories to set up a
working system. It may also use a solar tracking system to improve the system's overall
performance and include an integrated battery solution, as prices for storage devices are expected
to decline PV systems range from small, rooftop-mounted or building-integrated systems with
capacities from a few to several tens of kilowatts, to large utility-scale power stations of
hundreds of megawatts. Nowadays, most PV systems are grid-connected, while off-grid or stand-
alone systems only account for a small portion of the market (Hootman 2012). Classification of
solar cells briefly describes in following section.
Monocrystalline Solar Cells
This type of solar cell is made from thin wafers of silicon cut from artificially grown crystals.
These cells are created from single crystals grown in isolation, making them the most expensive
of the three varieties (approximately 35% more expensive than equivalent polycrystalline cells),

20
but they have the highest efficiency rating between 15-24% (Hootman 2012). Monocrystalline
Silicon is used in this project.
Polycrystalline Solar Cells
This type of solar cell is also made from thin wafers of silicon cut from artificially grown
crystals, but instead of single crystals, these cells are made from multiple interlocking silicon
crystals grown together, hence they are cheaper to produce, but their efficiency is lower than the
monocrystalline Solar cells, currently at 13-18% (Hootman 2012).
Thin Film Solar Cells
These are the cheapest type of solar cell to produce, are relatively new to market and are
produced very differently to the two other types. Instead of using crystals, Silicon is deposited
very thinly on a backing substrate. There are two real benefits of the amorphous solar cell; firstly
the layer of silicon is so thin it allows the solar cells to be flexible and secondly, they are more
efficient in low light levels (like during winter). This however comes at a price; they have the
lowest efficiency rating of all three types – approximately 7% – 9%, requiring approximately
double the panel area to produce the same output. In addition, as this is a relatively new science,
there is no agreed industry wide production technique, so they are not as robust as the other two
types (Hootman 2012).
Array Sizing and Energy Calculation
There is an online tool which is very user friendly called PV Watts. This tool is supported by the
National Renewable Laboratory (NREL). The calculator estimates the electricity production of a
grid-connected roof- or ground-mounted photovoltaic system based on a few simple inputs. To
use the calculator, type the address or geographic coordinates of the system's location, specify
the system size and array orientation, and provide some information about the system's cost and
electricity rates. PV Watts calculates estimated values for the system's annual, monthly and
hourly electricity production, and for the monetary value of the electricity. (NREL 2011)
4.2 Solar Water Heating
Solar water heating (SWH) is the conversion of sunlight into renewable energy for water
heating using a solar thermal collector. Solar water heating systems consist of various
technologies that are increasingly used worldwide. Since solar water heating is not included in
the target simulated buildings, they are not discussed in this report.

21
5. Plug Loads and Occupancy
Plug and process loads (PPLs) account for 33% of U.S. commercial building electricity
consumption (McKenney, et. al. 2010). Minimizing these loads is a significant challenge in the
design and operation of an energy-efficient building. (Lobato et al. 2011). (Lobato et al. 2012)
define PPLs as energy loads that are not related to general lighting, heating, ventilation, cooling,
and water heating, and that typically do not provide comfort to the occupants. The percentage of
total building energy use from PPLs is increasing. According to the U.S. Department of Energy
(DOE), by 2030, commercial building energy consumption is expected to increase by 24%; PPL
energy consumption is anticipated to increase by 49% in the same time frame (DOE 2010).
These trends illustrate the importance of PPL energy reduction to achieve an overall goal of
reducing whole-building energy consumption (Griffith 2007). Figure 9 will show commercial
building energy use breakdown.
Figure 9. Commercial Building Energy Use Breakdown (Griffith 2007)
Occupant Behavior
Occupant behavior affects the building energy use directly and indirectly by opening/closing
windows, turning on/off or dimming lights, turning on/off office equipment, turning on/off
heating, ventilation, and air-conditioning (HVAC) systems, and setting indoor thermal, acoustic,
and visual comfort criteria. Measured energy use of buildings demonstrated large discrepancies
even between buildings with same functions and located in similar climates. Among various
factors contributing to the discrepancies, occupant behavior is a driving factor. Occupant
behavior is also one of the most significant sources of uncertainty in the prediction of building
energy use by simulation programs due to the complexity and inherent uncertainty of occupant
behavior. With the trend towards low energy buildings that reduce fossil fuel use and carbon

22
emissions, getting occupants actively involved during the design and operation of buildings is a
key to achieving high energy performance without scarifying occupant comfort or productivity.
Pilot projects demonstrated that low energy systems, such as natural ventilation, shading to
control solar heat gains and glare, daylighting to dim lights, and demand controlled ventilation,
especially need the interactions and collaborations of occupants. Energy savings from 5 to 30%
were achieved by behavioral studies that motivate changes to occupant behavior (Tianzhen Hong
2013).
6. Modeling Simulation Results
This section includes, conventional and new building specifications, description of modeling
tools used in the project, building validation, which contains my simulation approach and tabular
inputs used for baseline buildings and energy efficient buildings. It also includes simulation
results for new buildings, older buildings and their comparison.
6.1 Building Specification
• Building Type: Office buildings
• Occupancy: 100Sqft/person
• Area: 50,000 Sqft and 100,000 SqFt
• Location: Phoenix, AZ, San Jose, CA, Chicago, IL
• Baseline: ASHRAE 90.1 2013, California Title 24 2013
• Modeling Tool: eQuest by Department of Energy
• Renewable Tool: PV Watts by NREL
• Internal Loads: Task lighting, area lighting, miscellaneous loads, and occupancy
• Miscellaneous Loads: Cooking equipment’s, plug loads, and computer server
Building Schematic
Figure 10. Building Schematic

23
In new construction for heating and cooling, ground source vertical closed loop heat pump is
used. Due to use of a ground source heat pump, there is only electrical energy consumption in
the building. The following energy efficient techniques used in the simulation. Default values in
eQuest have been selected for energy efficient features.
• Daylighting
• Natural ventilation
• Energy efficient building envelop
• Energy efficient lighting and plug loads
• Variable frequency drives
• Ground source heat pump for heating and cooling
• Ground source heat pumps for domestic hot water
Conventional construction, which is built in 1980s uses chillers and boilers for cooling and
heating. HVAC System type is multi zone air handler with hot water heating. No energy
efficiency techniques were used. Following are the details.
• No daylighting
• No natural ventilation
• Building envelop as per CA Title 24 1980 for location in California and ASHRAE 90.1
1980 for other locations
• Lighting and plug loads as per CA Title 24 1980 for location in California and ASHRAE
90.1 1980 for other locations
• No variable frequency drives
• Both electrical and natural gas consumption in the building. Natural gas used for both
domestic hot water and space heating
For sizing of solar array following parameters were used.
• DC system size depends on roof area of buildings. Calculated as, Size (kW) = Array Area
(m²) × 1 kW/m² × Module Efficiency (%)
• Monocrystalline PV module
• Fixed array type
• Array tilt 20 degree
• Azimuth angle 180 degree
• 60% of building roof area is covered with Solar array
Note: For a fixed array, the azimuth angle is the angle clockwise from true north describing the
direction that the array faces. An azimuth angle of 180° is for a south-facing array, and an
azimuth angle of zero degrees is for a north-facing array. All the new buildings are south facing
azimuth angle will be 180 degree for south facing array.

24
6.2 Modeling Tool
eQuest is designed to provide whole building performance analysis to buildings professionals,
i.e., owners, designers, operators, utility and regulatory personnel, and educators. Whole building
analysis recognizes that building is a system of systems and that energy responsive design is a
creative process of integrating the performance of interacting systems, e.g., envelop, fenestration,
lighting, HVAC, and domestic hot water (Hirsch 2012).
PV Watts Online Tool
PV Watts estimates the energy production and cost of energy of grid-connected photovoltaic
(PV) energy systems throughout the world. It allows homeowners, small building owners,
installers and manufacturers to easily develop estimates of the performance of potential PV
installations. PV Watts calculates estimated values for the system's annual, monthly and hourly
electricity production, and for the monetary value of the electricity (NREL 2011).
6.3 Building Specifications
Approach
• Modeled one floor baseline buildings with area of 50,000 and 100,000 Sqft
• Applying ASHRAE 90.1 2013 and CA Title 24 2013 standards and found out annual
electrical energy consumption
• Modeled same baseline buildings for three different locations; San Jose, CA, Phoenix,
AZ, Chicago, IL and found out annual electrical consumption
• Applying energy efficient techniques to baseline building to make it energy efficient
buildings and derived annual electrical consumption for three different locations
• By utilizing PV Watts online tool for sizing the solar array, derived electrical energy
production for one floor energy efficient buildings for all three locations
• Determined electrical energy consumption by gradually increasing floors for energy
efficient buildings for all three different locations
• Simultaneously sizing solar array for different floors to find out electrical energy
production
• After finding electrical energy consumption and production for different floors and
locations, the main aim is to determine maximum number of floors that can be built to
make net zero site energy using roof mounted solar PV.
Tabular Inputs for New Construction
Table 6-1 shows different inputs used in eQuest for baseline building, Energy Efficient
techniques and Net Zero Energy for different locations.

25
Table 6-1 Tabular inputs used in eQuest for baseline building, Energy Efficient techniques and
Net Zero Energy for different locations (San Jose, CA Chicago, IL and Phoenix, AZ)
Components Baseline Energy
Efficiency
Techniques
Net Zero Energy
Cooling: DX Coil EER: 10.4
(ASHRAE 90.1),
EER: 13.4 (B.
Griffith, 2007)
EER: 13.4 (B. Griffith,
2007)
EER: 9.6 (CA
Title 24)
Heating: Ground
Source Heat
pump
COP: 3.1
(ASHRAE 90.1),
COP: 4.2 (B.
Griffith, 2007)
COP: 4.2 (B. Griffith,
2007)
COP: 2.9 (CA
Title 24)
Variable Volume
Fan
Efficiency: 50%
(ASHRAE 90.1)
Efficiency: 70%
(B. Griffith, 2007)
Efficiency: 70% (B.
Griffith, 2007)
Efficiency: 50%
(ASHRAE 90.1)
Domestic Hot Water
Heater Fuel Electricity Electricity Electricity
Heater Type Heat pump Heat pump Heat pump
COP 7 (ASHRAE
90.1)
7 (ASHRAE
90.1)
7 (ASHRAE 90.1)
7 (CA Title 24) 7 (CA Title 24) 7 (CA Title 24)
Ground Source Heat pump
GSHP loop Head 71.6 ft.(ASHRAE
90.1)
71.6 ft.
(ASHRAE 90.1)
71.6 ft. (ASHRAE 90.1)
71.6 ft. (CA Title
24)
71.6 ft. (CA Title
24)
71.6 ft. (CA Title 24)
Ground Heat
Exchange (GHX)
type
Vertical well Vertical well Vertical well
Loop temp: 30 F min and 110
F Max (ASHRAE
90.1)
30 F min and 110
F Max (ASHRAE
90.1)
30 F min and 110 F Max
(ASHRAE 90.1)
Continued on the following page

26
30 F min and 110
F Max (CA Title
24)
30 F min and 110
F Max (CA Title
24)
30 F min and 110 F Max.
(CA Title 24)
Loop Flow Constant with no
Variable speed
drive (VSD)
Variable with
Variable speed
drive (VSD)
Variable with variable
speed drive (VSD)
Building Envelop
Window to wall
ratio
52.3% (ASHRAE
90.1)
30% (B. Griffith,
2007)
30% (B. Griffith, 2007)
52.3% (CA Title
24)
Window Glass
Type
Double clear
(ASHRAE 90.1)
Triple clear /Tint
(B. Griffith, 2007)
Triple clear /Tint (B.
Griffith, 2007)
Double clear (CA
Title 24)
Vertical Glazing
with U Factor
0.57 (ASHRAE
90.1) Btu/h.Ft2.F,
0.40 (B. Griffith,
2007) Btu/h.Ft2.F
0.40 (B.
Griffith,2007)Btu/h.Ft2.F
0.59 Btu/h.Ft2.F
(CA Title 24)
Steel Frame wall
U Factor
0.084 (ASHRAE
90.1) Btu/h.Ft2.F,
0.064 (B. Griffith,
2007) Btu/h.Ft2.F
0.064 (B. Griffith, 2007)
Btu/h.Ft2.F
0.082 Btu/h.Ft2.F,
(CA Title 24)
Roof Metal frame 0.055 Btu/h.Ft2.F
(ASHRAE 90.1),
0.065 Btu/h.Ft2.F
(CA Title 24)
0.023 Btu/h.Ft2.F
(B. Griffith, 2007)
0.023 Btu/h.Ft2.F (B.
Griffith, 2007)
Floors wood
Framed
0.051 Btu/h.Ft2.F
(ASHRAE 90.1),
0.047 Btu/h.Ft2.F
(B. Griffith, 2007)
0.047 Btu/h.Ft2.F (B.
Griffith, 2007)
0.071 Btu/h.Ft2.F
(CA Title 24)
Windows Double Pane
(ASHRAE 90.1)
Triple pane Triple pane
Double Pane (CA
Title 24)

27
Lighting Systems
Area Lighting Fluorescent light Fluorescent light Fluorescent light
Office 1.10 W/Ft2
(ASHRAE 90.1)
0.5 W/Ft2 (B.
Griffith, 2007)
0.5 W/Ft2 (B. Griffith,
2007)
1.10 W/Ft2 (CA
Title 24)
Corridor 0.66 W/Ft2
(ASHRAE 90.1)
0.5 W/Ft2 (B.
Griffith, 2007)
2007)
0.66 W/Ft2 (CA
Title 24)
Lobby 1.30 W/Ft2
(ASHRAE 90.1)
0.5 W/Ft2 (B.
Griffith, 2007)
2007)
1.10 W/Ft2 (CA
Title 24)
Rest rooms 0.98 W/Ft2
(ASHRAE 90.1)
0.7 W/Ft2 (B.
Griffith, 2007)
2007)
0.98 W/Ft2 (CA
Title 24)
Conference
rooms
1.30 W/Ft2
(ASHRAE 90.1)
0.6 W/Ft2 (B.
Griffith, 2007)
2007)
1.40 W/Ft2 (CA
Title 24)
Mechanical/
Electrical room
1.50 W/Ft2
(ASHRAE 90.1)
0.5 W/Ft2 (B.
Griffith, 2007)
2007)
0.70 W/Ft2 (CA
Title 24)
Computer Server
Room
1.50 W/Ft2
(ASHRAE 90.1)
1.1 W/Ft2 (B.
Griffith, 2007)
2007)
0.70 W/Ft2 (CA
Title 24)
Miscellaneous
load
0.75 W/Ft2
(Default eQuest)
0.6 W/Ft2 (B.
Griffith, 2007)
2007)

28
Passive architecture
Day lighting No Yes with Day
lighting Sensors
Yes with Day lighting
Sensors
Occupancy
sensors
No Yes Yes
Natural
Ventilation
No Yes Yes
Night Purge
ventilation
No Yes Yes
Waste Heat
Recovery
No Yes Yes
6.4 Modeling Results
Tables 6-2 to 6-7 show the output of new office building with different sizes, locations and
number of floors.
Table 6-2 Output of new office building with 50,000 Sqft in Phoenix, AZ for different number of
floors
Table 6-3 Output of new office building with 100,000 Sqft in Phoenix, AZ for different number
of floors
Floors Roof Area Annual
Electricity
Consumption
Annual
Electrical
Production
Net Zero Site
Energy (roof
mounted
solar PV)
1 50,000 Sqft 446,480 kWh 944,471 kWh Yes
2 25,000 Sqft 462,130 kWh 475,018 kWh Yes
3 16,670 Sqft 480,060 kWh 311,931 kWh No
Electricity
Consumption
Annual
Electrical
Production
Net Zero Site
Energy (roof
mounted solar
PV)
1 100,000 Sqft 870,360 kWh 1,888,942 kWh Yes
2 50,000 Sqft 900,800 kWh 944,471 kWh Yes
3 33,330 Sqft 918,520 kWh 623,862 kWh No

29
Table 6-4 Output of new office building with 50,000 Sqft in San Jose, CA for different number
of floors
Table 6-5 Output of new office building with 100,000 Sqft in San Jose, CA for different number
of floors
Table 6-6 Output of new office building with 50,000 Sqft in Chicago, IL for different number of
floors
Electricity
Consumption
Annual
Electrical
Production
Net Zero
Site
Energy (roof
mounted
solar PV)
1 50,000 Sqft 378,190 kWh 824,189 kWh Yes
2 25,000 Sqft 390,060 kWh 413,649 kWh Yes
3 16,670 Sqft 397,330 kWh 275,248 kWh No
Electricity
Consumption
Annual
Electrical
Production
Net Zero
Site
Energy (roof
mounted
solar PV)
1 100,000 Sqft 748,640 kWh 1,648,377 kWh Yes
2 50,000 Sqft 761,470 kWh 824,189 kWh Yes
3 33,330 Sqft 770,620 kWh 550,496 kWh No
Electricity
Consumption
Annual
Electrical
Production
Net Zero
Site
Energy (roof
mounted
solar PV)
1 50,000 Sqft 328,430 kWh 677,148 kWh Yes
2 25,000 Sqft 336,070 kWh 339,882 kWh Yes
3 16,670 Sqft 342,030 kWh 230,000 kWh No

30
Table 6-7 Output of new office building with 100,000 Sqft in Chicago, IL for different number
of floors
Net Zero Energy of Conventional Construction
• Building Type: Office building
• 1980s construction
• Area: 100,000 SqFt
• Location: Phoenix, AZ, San Jose, CA, Chicago, IL
• Modeling Tool: eQuest by Department of Energy
• Renewable Tool: PV Watts by NREL
• Occupancy: 100 SqFt/person
• No passive architecture
• Standard Chillers and Boilers
• Baseline lighting density (CA title 24, ASHRAE 90.1)
• Baseline building envelop (CA title 24, ASHRAE 90.1)
• No Variable Frequency Drive
The section from Tables 6-8 to 6-10 gives an output of conventional construction office building
for 100,000 Sqft with different locations and number of floors
Electricity
Consumption
Annual
Electrical
Production
Net Zero
Site
Energy (roof
mounted
solar PV)
1 100,000 Sqft 664,490 kWh 1,354,297 kWh Yes
2 50,000 Sqft 676,660 kWh 677,148 kWh Yes
3 33,330 Sqft 683,640 kWh 338,574 kWh No

31
Location: San Jose, CA
Table 6-8 Output of conventional office building with 100,000 Sqft in San Jose, CA for different
number of floors
Location: Phoenix, AZ
Table 6-9 Output of conventional office building with 100,000 Sqft in Phoenix, AZ for different
number of floors
Note: One floor can be converted into Net Zero Source Energy in both San Jose, CA and
Phoenix, AZ if annual gas consumption converted into electrical consumption.
Electricity
Consumption
Annual
Electrical
Production
Annual Gas
Consumption
kBtu
Net
Zero Site
Energy
(roof
mounted
solar PV)
1 100,000
Sqft
903,150 kWh 1,648,377
kWh
1,248,900 Yes
2 50,000
Sqft
944,250 kWh 824,189
kWh
1,296,900 No
3 33,330
Sqft
972,840 kWh 550,496
kWh
1,370,300 No
Electricity
Consumption
Annual
Electrical
Production
Annual Gas
Consumption
kBtu
Net Zero
Site
Energy
(roof
mounted
solar PV)
1 100,000
Sqft
1,151,600 kWh 1,888,942
kWh
771,300 Yes
2 50,000
Sqft
1,215,500 kWh 944,471
kWh
831,840 No
3 33,330
Sqft
1,265,600 kWh 623,862
kWh
893,550 No

32
Location: Chicago, IL
Table 6-10 Output of conventional office building with 100,000 Sqft in Chicago, IL for different
number of floors
Comparison between New and Conventional Building Parameters
In this section from Tables 6-11 to 6-13 gives comparison between new and conventional
building parameters for 100,000 Sqft for different location
Table 6-11 Comparison between new and conventional building parameters for Phoenix, AZ
with different number of floors.
Electricity
Consumption
Annual
Electrical
Production
Annual Gas
Consumption
kBtu
Net Zero
Site
Energy
(roof
mounted
solar PV)
1 100,000
Sqft
962,800 kWh 1,354,297
kWh
1,960,000 No
2 50,000
Sqft
1,012,000 kWh 677,148
kWh
2,008,000 No
3 33,330
Sqft
1,047,300 kWh 338,574
kWh
2,051,000 No
Sector Floors New building Conventional building
Space Cooling
1 233,030 kWh 245,200 kWh
2 256,780 kWh 293,700 kWh
3 268,280 kWh 317,900 kWh
Space Heating
1 0 337,360 kBtu
2 0 437,830 kBtu
3 0 499,610 kBtu

33
Table 6-12 Comparison between new and conventional building parameters for San Jose, CA
with different number of floors.
Hot Water
1 68,230 kWh 393,930 kBtu
2 68,230 kWh 394,000 kBtu
3 68,230 kWh 393,940 kBtu
Ventilation Fans
1 34,580 kWh 98,200 kWh
2 43,170 kWh 113,900 kWh
3 51,470 kWh 120,600 kWh
Pump & Auxiliary
1 18,520 kWh 48,900 kWh
2 20,900 kWh 62,800 kWh
3 21,520 kWh 69,300 kWh
Space Cooling
1 141,510 kWh 155,520 kWh
2 155,550 kWh 179,700 kWh
3 162,860 kWh 191,800 kWh
Space Heating
1 0 773,200 kBtu
2 0 821,900 kBtu
3 0 895,400 kBtu
Hot Water
1 70,150 kWh 475,700 kBtu
2 70,150 kWh 475,000 kBtu
3 70,150 kWh 474,900 kBtu

34
The space heating shows negligibly small at San Jose, CA and Phoenix, AZ; most probably due
to higher thermal mass and higher U value of insulation. The same building was simulated using
boiler for space heating keeping all the other parameters same. The result was shown to be, 2800
kBtu. Repeated simulation were made and small values were shown for space heating which may
be an artifact of the simulation.
Table 6-13 Comparison between new and conventional building parameters for Chicago, IL with
different number of floors.
Ventilation Fans
1 17,830 kWh 71,200 kWh
2 20,790 kWh 76,200 kWh
3 23,100 kWh 78,500 kWh
Pump & Auxiliary
1 12,350 kWh 41,260 kWh
2 13,620 kWh 51,500 kWh
3 14,460 kWh 56,800 kWh
Space Cooling
1 89,010 kWh 152,130 kWh
2 102,650 KWh 184,000 kWh
3 117,520 kWh 200,000 kWh
Space Heating
1 33,260 kWh 1,416,500 kBtu
2 36,870 kWh 1,475,000 kBtu
3 40,210 kWh 1,517,350 kBtu
Hot Water
1 55,910 kWh 532,500 kBtu
2 55,910 kWh 533,000 kBtu
3 55,910 kWh 533,650 kBtu

35
Summarization of Results
New building: By roof mounted solar array and by using energy efficient techniques it is
possible to make buildings a net zero site energy, two floors can be built regardless of location
and area. For more floors, then it has to make use of surrounding space like a parking lot.
Conventional Building: By simulating and sizing solar array for conventional buildings with
same area and location, it is observed that only one floor can be zero net site energy using roof
mounted solar PV if natural gas consumption is converted into electrical consumption. With
comparatively high electrical energy consumption to that of new construction, further floors
cannot be make zero net site energy using roof mounted solar PV. As it is conventional
construction, there is no ground source heat pump installed in the building so has both electrical
and natural gas consumption. By having natural gas consumption, it is very difficult to make
more than one floor zero net site energy using roof mounted solar PV.
7. Simulation Verification
To verify simulation, I modeled similar building whose results are available to us. In this case I
modeled Research Support Facility (RSF) office, which is Net Zero Energy located in Colorado
(Hootman 2012). I used all the energy efficient techniques to verify my simulation project.
Project Data (Hootman 2012):
Building Area: 222,000 Sqft
Floors: 4 story building
Location: Denver, CO
Ventilation Fans
1 14,390 kWh 65,820 kWh
2 16,700 kWh 80,500 kWh
3 17,800 kWh 85,500 kWh
Pump & Auxiliary
1 10,080 kWh 50,270 kWh
2 11,490 kWh 61,300 kWh
3 12,410 kWh 67,300 kWh

36
Climate Zone: 5B; Cool, Dry
Occupant: 822
Occupied hours per week: 50 Hrs.
Roof Area: 69, 950 Sqft
Data Center Energy: 65 Watts/person for 1200 occupants on campus will be 683,280 kWh/year
Total Energy Consumption: 2254 MWh/yr
My simulation Output:
Data Center Energy: 65 Watts/person for 1200 occupants on campus will be 683,280 KWh/ year
Total Energy consumption: 2285 MWh
Table 6-14 Comparison between RSF building real data and my simulation output
Points RSF building real data Simulation output
Final Design Energy Use
intensity
33.2 kBtu/ft2/yr 35.12 kBtu/ft2/yr
Annual Energy consumption 2254 MWh/yr 2285 MWh/yr
By modeling RSF building and getting output similar to real data verifies all the energy efficient
techniques used in simulation project.
8. Future of Net Zero Energy Building
Net zero energy (NZE) is still a relatively new movement; only a small percentage of current
building construction has a goal of NZE. However, efforts are increasing, with a doubling in the
number of commercial NZE buildings over the last two years. Policies and programs can
dramatically change the landscape for Net Zero Energy (NZE) buildings. California Public
Utilities Commission (CPUC) adopted the big bold Initiative, which focused that all new
residential and commercial construction be NZE by 2020 and 2030 respectively. As per my
view, reduction, reuse, and renewables are three main steps towards zero net energy. Reduction
must come first, ideally by load reduction followed by efficiency measures. Reuse comes next,
with a focus on creatively putting waste energy in the systems back into beneficial use.
Renewable will produce energy which will help to achieve net zero design. Below are my
suggestions which can be helpful towards future of Net Zero Energy Buildings.

37
• Passive architecture is a fundamental prerequisite for net zero energy buildings.
Appropriate use of passive architecture can reduce in significant amount of heating and
cooling load.
• Use of ground source heat pump instead of boilers and chillers for heating, cooling, and
domestic hot water can reduce in significant amount of electrical consumption in the
buildings and there will not be any natural gas consumption in the buildings.
• Using energy efficient lighting fixtures and lighting controls can lower electrical
consumption
• Using variable speed drives can lower electrical consumption
• Waste heat recovery technique is also very useful towards energy reduction process
• Reduction in building plug loads and behavioral changes also very important towards net
zero energy.
9. References
Athienitis, A. 2006. Design and Optimization of Net Zero Energy Solar Homes. ASHRAE Report,
American Society of Heating, Refrigerating and Air-Conditioning Engineers Inc.
Griffith, B., N. Long, P. Torcellini, and R. Judkoff. 2007. Assessment of the Technical Potential for
Achieving Net Zero-Energy Buildings in the Commercial Sector. Technical Report,
National Renewable Laboratory.
California Public Utilities commission. 2008. Accessed December 6, 2015.
http://www.cpuc.ca.gov/NR/rdonlyres/C27FC108-A1FD-4D67-AA59-
7EA82011B257/0/3.pdf.
Codes, E. 2012. "Lighting Development, Adoption and Compliance Guide." Building Technology
program. September. Accessed December 2, 2015.
https://www.energycodes.gov/sites/default/files/documents/Lighting_Resource_Guide.
pdf.
Collyer, B. 2012. Zero Net Energy Program. Pacific Gas and Electric Company Report, San
Francisco: Pacific Gas and Electric Company.
Department of Energy. 2008. Accessed December 6, 2015.
http://energy.gov/energysaver/solar-water-heaters.
—. 2008. Accessed November 18, 2015. http://energy.gov/energysaver/heat-pump-systems.

38
—. 2009. eQUEST. Sepetmber. Accessed November 2015. http://www.doe2.com/equest/.
Haglund, K. 2012. Department Of Energy. Northenstar. November. Accessed November 18,
2015.
http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/measure_g
uide_windows.pdf.
Harrell, G. 2009. ENERGY MANAGEMENT SERVICES. PhD Thesis, Tennessee: National Renewable
Laboratory.
Hirsch. 2012. eQuest Introductory Tutorial. Tutorial, Camarillo: Department of Energy.
Hong, T., H. Lin. 2013. Occupant Behavior: Impact on Energy Use of Private Offices. Publish
Report, Ernest Orlando Lawrence Berkeley National Laboratory, 12.
Hootman, T. 2012. Net Zero Energy Design: Commercial buildings, New jersey: John Wiley &
Sons, Inc.
Kwatra, S., J. Amann, H. Saches. 2013. Miscellaneous Energy Loads in Building. Published
Report, Washington: American Council of Energy Efficienct Economy.
National Renewable Energy Laboratory (NREL). 2011. PV Watts. Accessed December 10, 2015.
http://pvwatts.nrel.gov/pvwatts.php.
Sheppy, M., C. Lobato, S. Pless, L. Polese, and P. Torcellini. 2012. Assessing and Reducing Plug
and Process Loads in Office Buildings. Fact Sheet, Denver: National Renewable Research
Laboratory.
Torcellini, P. 2006. Zero Energy Buildings: A Critical Look at the Definition. Published Report,
Denver: National Research Laboratory, 15.
Torcellini, P., S. Pless, and C. Lobato. 2010. Main Street Net-Zero Energy Buildings: The Zero
Energy Method in Concept and Practice. Case Study, Phoenix: National Research
Laboratry.

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