Standard 189.1 sets requirements for high-performance green buildings that go beyond energy efficiency standards in 90.1. It includes provisions for site sustainability, water use efficiency, indoor environmental quality, and reducing atmospheric and resource impacts. The standard provides prescriptive and performance compliance paths and is estimated to achieve 30% average energy savings compared to 90.1. It also specifies construction and operation plans to help achieve high-performance operation.
ASHRAE Journal Supplemental Guide to Standard189.1
1. This supplement was published in ASHRAE Journal, June 2010. Copyright 2010 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Posted
at www.ashrae.org. This article may not be copied and/or distributed electronically or in paper form without permission of ASHRAE. For more information about
ASHRAE Journal, visit www.ashrae.org.
’S June 2010
Guide to Standard 189.1
Balancing Environmental Responsibility, Resource Efficiency & Occupant Comfort
IEQ
Site Construction
& Plans for
Sustainability
Operation
Water Use Atmosphere,
Efficiency Materials,
Resources
Energy
Efficiency
3. ASHRAE Journal’s
Commentary
Guide to Standard 189.1
Standardizing High Performance
T
hirty-five years ago, ASHRAE set the foundation for net-zero-energy buildings. Standard 189.1 provides that
long-needed green building foundation for those who strive to
energy conservation with the development of Stan-
design, build and operate green buildings.
dard 90, which is the first standard in the nation set- As ASHRAE President Gordon Holness said, “The far-
reaching influence of the built environment necessitates
ting requirements for energy efficiency in buildings. The stan-
action to reduce its impact. Provisions in the standard
dard, developed in reaction to the 1970 oil embargo and can reduce negative environmental impacts through high-
performance building design, construction and operations
resulting energy crisis, now serves as the basis for building
practices. Ultimately, the aim is not just energy efficiency but
codes and the standard for building design and construction a balance of environmental responsibility, resource efficiency,
occupant comfort and well-being and community sensitivity,
throughout the United States, influencing designs worldwide.
all while supporting the goal of sustainable development.”
Earlier this year, ASHRAE published another standard When I think about the standard, I envision a group
that is poised to have the same impact as 90.1. Together of building blocks representing ASHRAE standards and
with the U.S. Green Building Council and the Illuminating guidelines, including Standard 55, Thermal Environmental
Engineering Society of North America (IES), we released Conditions for Human Occupancy; 90.1, Energy Standard
ANSI/ASHRAE/USGBC/IES Standard 189.1, Standard for the for Buildings Except Low-Rise Residential Buildings; 62.1,
Design of High-Performance, Green Buildings Except Low- Ventilation for Acceptable Indoor Air Quality; 180, Standard
Rise Residential Buildings. Practice for Inspection and Maintenance of Commercial
Where Standard 90.1 sets the foundation for energy Building HVAC Systems and Guideline 0, The Commissioning
efficiency, Standard 189.1 builds on that foundation with Process. Requirements from these existing documents
additional energy efficiency measures and renewable served as cornerstones in development of Standard 189.1,
energy requirements and then goes a step further with along with guidance from USGBC, IES, the U.S. Department
requirements for site sustainability, water use efficiency, of Energy and many other agencies and groups. This
indoor environmental quality and the building’s impact on standard is truly the most diverse in the Society’s history and
the atmosphere, materials and resources. that is precisely why ASHRAE partnered with USGBC and IES
We took another step in March toward strong sustainable to ensure that knowledge from all aspects of the sustainable
buildings by joining forces with the International Code marketplace were part of the process.
Council. Standard 189.1 became a jurisdictional compliance The standard covers the same group of building spaces
option in the Public Version 1.0 of the International Green as Standard 90.1 but only for those buildings intended as
Construction Code (IGCC) published by the International high performance. It covers all nonresidential spaces and
Code Council. The IGCC regulates construction of new and all residential spaces in buildings more than three stories.
remodeled commercial buildings, and Standard 189.1 Within these buildings, Standard 189.1 applies to new and
serves as a strong technical backbone of that document. renovated buildings and their systems; and new or renovated
Together, IGCC and Standard 189.1 provide the first set portions of buildings and their systems.
of model codes and standards for green building in the The standard includes mandatory provisions in each section
United States. For ASHRAE Journal readers, this means with an option to use a prescriptive path or performance path
that requirements to help you in the design, operation and for compliance. The mandatory provisions must be complied
maintenance of green buildings can soon be adopted by with by all projects. The prescriptive option contains additional
local and state code communities. The interest in green criteria specified in a manner that provides a simple way
buildings already has shown us that the marketplace to show compliance that involves little or no calculations.
is ready for a green building standard that sets energy- The performance option contains an alternate way to show
efficiency requirements beyond those in Standard 90.1, compliance that provides more design flexibility and is typically
pushing the building industry toward the goal of future more complex than the prescriptive option.
June 2010 ASHRAE Journal’s Guide to Standard 189.1 S3
6. ASHRAE Journal’s
Guide to Standard 189.1
The emergence of green building codes and standards...
is an important next step for the green building movement.
LEED & Green Building Codes
By Brendan Owens, P.E., Member ASHRAE; and The norm is that codes improve incrementally, approxi-
Jeremy Sigmon mately a three-year cycle. As ideas originally pioneered in
B
LEED begin to emerge as acceptable industry practice, a
uilding codes are the tools we use to ensure growing community of professionals has recognized the
the basic health and safety of a building’s oc- need for enforceable codes and standards for large-scale
cupants. They have long played an important adoption and implementation by building departments
and regulatory authorities. This far more inclusive perspec-
role in establishing minimum standards of practice to
tive of risk and responsibility recognized by LEED has
ensure fire, structural and sanitary safety in homes, required not an incremental, but instead a very signifi-
schools, offices, and public buildings of all types. cant leap forward in the scope of the building codes.
Green building rating systems, such as U.S. Green Broad stakeholder input and community consensus have
Building Council’s LEED certification program, have been recently led to the development of green building codes and
working to address an expanded spectrum of risks to hu- standards that can be adopted and enforced by jurisdictions
man and environmental health that are related to what we in line with their commitments to safeguarding environ-
build, how we build, where we build, and how we operate mental and public health. In response to demand for a clear
buildings over the long term. After 17 years since USGBC’s message from their membership, the International Code
founding and tens of thousands of volunteer hours, LEED Council (ICC) launched the development of the Internation-
is the most widely accepted green building rating system, al Green Construction Code (IGCC) with cooperating spon-
and has been credited with inspiring innovation, driving sors AIA and ASTM. Recognizing the value of the several
demand for high performance buildings and communi- years of expert content development in ASHRAE Standard
ties, and changing the way that much of the building 189.1, and ICC’s unparalleled delivery model that reaches
industry approaches design, construction and operations. all 50 states and more than 22,000 local jurisdictions,
LEED and the codes have always strived to work to- ICC, AIA and ASTM worked together with ASHRAE, IES
gether as complementary and compatible elements in the and USGBC to launch a joint effort to support the IGCC
building process. But before attempting above-code mea- with Standard 189.1 as an alternate path to compliance.
sures in energy savings, water efficiency, CO2 emissions Standard 189.1 is a set of technically rigorous require-
reduction, improved indoor environmental quality, or ments that, like IGCC, covers criteria including water use
stewardship of resources and sensitivity to their impacts, efficiency, indoor environmental quality, energy efficiency,
green buildings require minimum compliance with base- materials and resource use, and the building’s impact on its
line codes in a given jurisdiction. LEED’s recognition of site and its community. Written by experts representing all
ASHRAE Standards 90.1, 62 and 55, as well as standards areas of the building industry and developed in partnership
set by the California Air Resources Board and the Sheet
About the Authors
Metal and Air-Conditioning Contractors’ National As-
Brendan Owens, P.E., is vice president, LEED Technical Development
sociation are a few examples of how LEED has encour- and Jeremy Sigmon is manager, building codes advocacy at the U.S.
aged benchmarking against industry-accepted standards. Green Building Council in Washington, D.C.
S6 ASHRAE Journal’s Guide to Standard 189.1 ashrae.org June 2010
8. with IES and USGBC the standard Standards Code, is an important next able by regulatory jurisdictions. The
was three years in the making. step for the green building movement, IGCC and its 189.1 compliance path
The emergence of green building establishing a much-needed rubric provide a substantially improved
codes and standards, like the IGCC for high-performance green buildings minimum baseline for the design and
and the California Green Building that is adoptable, usable and enforce- performance of new and renovated
buildings, allowing all new build-
ings to reap the rewards of improved
design and construction practices.
Major advances in codes and stan-
dards like these make it possible to
accelerate the technical development of
LEED, allowing exemplary leadership
in green building design, construction
and operation to take even greater
steps forward. The IGCC provides a
substantially enhanced baseline that
jurisdictions can couple with LEED-
based incentive programs. Green
building rating systems play a distinct
and complementary role to green
building codes. Given the strength of
its content, its enforceable language,
and its applicability to all commercial
buildings, widespread adoption of
IGCC and its 189.1 compliance path
will catapult the commercial build-
ing sector forward with measurable
achievements and results that are
responsive to the economic, environ-
mental and health challenges at hand.
The adoption and enforcement of
green building standards and codes
advances USGBC’s mission to trans-
form the way our industry designs,
constructs and operates buildings.
By integrating tried-and-tested green
building practices into minimum code
language, green building standards also
provide USGBC, LEED and the green
building industry the freedom to go
farther and faster, blazing new trails
towards a truly sustainable future. But
it’s not a choice between green building
codes or green building rating systems—
it’s both these codes and rating systems
working together, learning from one
another, and continuously improving
content, implementation, and results.
www.info.hotims.com/30916-60
S8 ASHRAE Journal’s Guide to Standard 189.1 June 2010
10. ASHRAE Journal’s
Guide to Standard 189.1
Right Start,
Right Result:
Beginning
With the Site
By Anthony C. Floyd, AIA; Tom Lawrence, Ph.D., P Member ASHRAE; and Martha G. VanGeem, P Member ASHRAE
.E., .E.,
S
ite sustainability addresses ning, protect environmentally sensi- Mandatory Provisions
the environmental impacts tive lands, reduce heat island effect, Mandatory site provisions in-
minimize site light pollution, maximize clude site selection, mitigation of
involved in the process
pervious surfaces, retain native and heat island effect and the reduc-
of site design, development and biodiverse vegetation and manage tion of light pollution (Figure 1).
post-development activities. Build- on-site storm water through reuse,
ings and associated development infiltration or evapotranspiration. Site Selection
often disrupts natural ecosystems The intent of this section is to
and increases the negative effects minimize development on greenfields
Figure 1 Compliance paths.
and undeveloped sites. Development
of erosion, storm water runoff and
Mandatory Provisions must occur on sites that have exist-
summer heat sinks. The loca- Site Selection: Section 5.3.1 ing infrastructure, including building
tion of a building site can impact Mitigation of Heat Island Effect: Section 5.3.2 reuse and modifications to an exist-
greenhouse gas emissions and Reduction of Light Pollution: Section 5.3.3 ing building envelope. This includes
other pollutants based on avail-
able options for alternative modes Then, Choose One: About the Authors
Prescriptive Option Anthony C. Floyd, AIA, is senior green building
of transportation including pedes- consultant for the City of Scottsdale in Arizona.
Site Development: Section 5.4.1
trian proximity to basic services Tom Lawrence, Ph.D., P.E., is public service
or
associate, Faculty of Engineering, University of
and residential communities.
Performance Option Georgia, in Athens, Ga. Martha G. VanGeem,
The intent of site sustainability Site Development: Section 5.5.1 P.E., is a principal engineer, Building Science and
is to support smart growth plan- Sustainability, at CTLGroup, Skokie, Ill.
S10 ASHRAE Journal’s Guide to Standard 189.1 ashrae.org June 2010
11. Section 5:
Site
Figure 2 Sample map of pedestrian Figure 3 Sample diagram of hardscape
Sustainability
connectivity in the immediate area shading cast by a building on summer solstice.
surrounding the building site. The intent of site sustainability
is to support smart growth
planning, protect environmen-
tally sensitive lands, reduce
heat island effect, minimize
3 p.m. Summer Solstice site light pollution, maximize
pervious surfaces, retain native
with a solar reflective index (SRI) of at
least 29 (Figure 3). The shade coverage and biodiverse vegetation and
on hardscape must be based on the
manage on-site storm water.
arithmetic mean of the shade coverage
calculated at 10 a.m., noon, and 3 p.m.
development on existing greyfields on summer solstice. Climate Zones 6, 7
or mitigated brownfield sites. and 8 are exempt from this requirement.
Development cannot occur on a green- At least 30% of east and west above-
field site unless conditions exist that sup- grade walls must be shaded from simulation in accordance with Energy
port pedestrian connectivity in the imme- grade level to a height of 20 ft (6 m) Efficiency Sections 7.5.2 and 7.5.3.
diate area surrounding the site (Figure 2). by any one or combination of strate- The sidebar covers the rela-
These conditions include proximity to resi- gies involving vegetation, building tionship between heat island ef-
dential density (10 units per acre), 10 basic projections, architectural screening fect and building heat gains.
services (with 0.5 mile [0.8 km]) and train elements, existing buildings and/or
service (within 0.5 mile [0.8 km]) or other topographical land features such as Reduction of Light Pollution
adequate transit service (within 0.25 mile hillsides (Photos 1 and 2). The shade The intent of this section is to
[0.4 km]). Finally, development can occur coverage calculations must be based on minimize nighttime site illumina-
on a greenfield site that is classified as summer solstice at 10 a.m. for eastern tion. Adverse effects include light
agricultural, forest or designated park land exposed walls and 3 p.m. for western trespass, glare, sky glow, decreased
when the specific function of the building exposed walls. There are a number visibility and wasted energy.
is related to the respective use of the land. of exceptions based on east/west Light pollution is a broad term used
In addition to site selection, Stan- wall orientation and climate zone. to describe unwanted or unneces-
dard 189.1 limits development in flood In Climate Zones 1, 2 and 3, at least sary nighttime illumination, classified
hazard areas, fish and wildlife habitat 75% of the roof surface must comply as light trespass, glare and skyglow.
conservation areas, and wetlands. with one or a combination of strategies Light trespass is light that strays from
involving a minimum solar reflectance the intended purpose and becomes
Mitigation of Heat Island Effect index (SRI) of 78 for a low-slope roof an annoyance, a nuisance, or a detri-
The intent of this section is to (≤2:12), and an SRI of 29 for a steep- ment to visual performance.1 Sky-glow
minimize the effect of heat-absorbing sloped roof (>2:12), vegetated roof- is the brightening of the night sky
materials used for site hardscape, ing, roof-covered solar energy systems that results from the reflection of
walls and roofs. At least 50% of the and/or a roof complying with ENERGY radiation.1 Glare refers to light that
site hardscape must be provided by STAR criteria. An exception exists hinders or bothers the human eye.2
any one or combination of strategies for roofs used to cover parking and The light pollution requirements
involving shade provided by vegetation, for buildings that demonstrate energy in Standard 189.1 are applied in five
structures and/or paving materials cost savings through an energy analysis different lighting zones (Table 1). These
June 2010 ASHRAE Journal’s Guide to Standard 189.1 S11
12. Photo 1 (left) West wall protection in Climate
Zone 2 (photo: Will Bruder + Partners).
Photo 2 (below) Shade on the west wall
in Climate Zone 5 (photo: CTLGroup).
lighting zones are defined to reflect different nighttime ambi-
ent lighting conditions ranging from inherently dark to higher
ambient urban settings. The lower lighting zones (LZ0) have
much more restrictive requirements than the higher zones.
Based on the type of light pollution, the building project must
use the backlight, uplight and glare (BUG) ratings developed
in IESNA TM-15 to determine fixture requirements for the
various lighting zones. This section also requires adherence
to the exterior lighting power allowances of ASHRAE/IES
Standard 90.1 Addendum i in an attempt to balance visual roofs, porous pavers, permeable pavement or open-graded
needs with the desire to eliminate unnecessary light. aggregate (Photo 3). A number of exceptions are based on the
percentage of rainfall that is captured and reused for site or
Prescriptive Option building water use. There is also an exception for locations
For those building projects choosing the prescriptive with an average annual rainfall of less than 10 in. (254 mm).
compliance path, additional site-related requirements must
be followed to demonstrate compliance with the Stan- Greenfield Sites
dard. These requirements address the effective pervious- A minimum of 20% of a site must consist of local
ness of surfaces and the preservation of native plants. native plants or adapted plants based on predevelop-
ment site conditions. A minimum of 60% of such veg-
Effective Pervious Area etated area must consist of biodiverse plantings. Once
At least 40% of the site must incorporate any one or com- again, there is an exception for locations with an aver-
bination of strategies involving native vegetation, vegetated age annual rainfall of less than 10 in. (254 mm).
Exterior Zone & Lighting Level
Photo 3 Pervious concrete (photo: CTLGroup).
LZ0: Very Dark Remote fire station located in an undeveloped portion of a National Park
LZ1: Dark Gas station in a rural location outside a small town
LZ2: Low Grocery store adjacent to a residential neighborhood
LZ3: Medium Commercial district including retail and restaurant establishments
LZ4: High Hotel located in a high density, metropolitan area
Table 1 Lighting zone designations.
S12 ASHRAE Journal’s Guide to Standard 189.1 ashrae.org June 2010
14. Figure 4 Rainwater collection and reuse. Figure 5 On-site infiltration of rainwater (figure: Ann Audrey).
Perforated Pipe Non-Perforated Pipe
Rainwater
Collection
Ground
Level
Rainwater Reuse
10 ft or Greater to
Building Foundation
Storage Level
Performance Option the average annual rainfall to be managed through infiltration,
For building projects that do not follow the prescriptive op- reuse or ET. Whereas greyfield and brownfield sites require 40%
tion, the performance option provides an alternative method to and projects in an existing building envelope require only 20%.
demonstrate compliance with requirements for on-site retention,
collection and/or reuse of rainfall (Figures 4 and 5). As such, a References
percentage of the average annual rainfall on the development 1. IESNA. 2000. Technical Manual TM-10–00, Ad-
dressing Obtrusive Light (Urban Sky Glow and Light Tres-
footprint (on-site impervious surfaces) must be managed through pass) in Conjunction with Roadway Lighting. New York:
infiltration, reuse or evapotranspiration (ET) based on whether the Illuminating Engineering Society of North America.
site is on an existing building site, greyfield, brownfield or green- 2. NEMA. 2000. White Paper on Outdoor Lighting Code Issues.
field site. Existing greenfield sites require a minimum of 50% of Rosslyn, Va.: National Electrical Manufacturers Association.
Urban Heat Island Effect and Building Heat Gain
Confusion can easily arise when trying to balance the
impact of the building surface reflectivity (expressed as
SRI) on the urban heat island effect with the impact of
building SRI or shading on the overall heat gain to the How
building and its resulting impact on cooling or heat-
ing loads. SRI takes into account thermal emittance
as well as solar reflectance of building materials.
Cool
The requirements of Section 5 deal with the impacts
on the surrounding environment external to the build- Roofs Conventional Roof Cool Roof
Reflects 30% to 60% Reflects up to 80%
ing. The urban heat island effect is a well-documented
of incident solar. of incident solar.
phenomenon that is caused by a number of factors, Work Absorbs 40% to 70% Absorbs ~20%
one of which is the absorption and later release of (heats roof and adds
the sun’s energy into the local atmosphere and sur- to cooling load and
urban heat island).
roundings. In this case, setting sufficiently high SRI
values (or inclusion of shading provisions) will mini-
mize the absorption of the sun’s energy by the build- dominated environment the absorption of solar energy
ing exterior and reradiation or convective heat to the by the envelope overall is a good thing overall (although
local environment (air and adjacent surfaces). not a lot of solar energy is available for absorption in the
How much of the sun’s energy gets absorbed by the winter in most cold climates). The opposite is true for
building envelope impacts the building cooling and cooling-load-dominated climate zones. Cooling load domi-
heating loads to some extent, and the requirements in nated climate zones also would tend to have more of a
Section 5.3.2 were written to take into account cli- problem with urban heat islands than heating-dominated
mate zone differences. For example, in a heating-load- climates, at least on a total number of hours per year.
S14 ASHRAE Journal’s Guide to Standard 189.1 ashrae.org June 2010
16. ASHRAE Journal’s
Guide to Standard 189.1
Addressing Unnecessary
Water Waste in Buildings
By John Koeller and Katherine Hammack, Member ASHRAE cant, yet attainable, limits to monitor
W
and manage water consumption.
hen we think about water “At Least 36 U.S. States Section 6 of the Standard, “Water
shortages, we think about Face Water Shortage.” Use Efficiency,” details mandatory
a local problem, possibly in According to the Organisation for measures for water use efficiency that
Economic Co-operation and De- are required on all projects. There
our town or city, state or region. We
velopment (OECD), “By 2030, the are two pathways for projects to
usually don’t regard such problems number of people living under severe meet the remainder of the require-
as particularly worrisome, sharing water stress, leaving aside possible ments. Projects must follow either:
confidence that the situation will impacts of climate change, is expected • The prescriptive pathway, which
be readily handled by investment to rise to 3.9 billion, nearly half of outlines a series of specific
in infrastructure, conservation, or the projected world population.” water-saving strategies; or
Water shortages are an is- • A performance option, which
other management strategies.
sue. Therefore, guidance and allows a project’s overall water use
But, it’s not that simple. stricter building codes regarding to be calculated and compared
Headlines inform us that: the use of water are critical. to a maximum baseline level.
“Global Water Shortage ASHRAE/USGBC/IES Standard
Looms In New Century”; 189.1, Standard for the Design of High-Per- About the Authors
John Koeller is a principal at Koeller and
“Four Billion People Threat- formance Green Buildings Except Low-Rise
Company in Yorba Linda, Calif. Katherine
ened by Water Shortages if World Residential Buildings, addresses water Hammack is senior manager, climate change
Leaders Stumble at 2010’s First waste in buildings and on surround- and sustainability services at Ernst & Young LLP
Climate Change Hurdle”; and ing landscapes. It establishes signifi- in Phoenix.
S16 ASHRAE Journal’s Guide to Standard 189.1 ashrae.org June 2010
17. ASHRAE Journal’s
Guide to Standard 189.1
Section 6:
Water Use
Plumbing Fixture Maximum Volume Efficiency
Water Closets (Toilets)
• Flushometer Valve Type Single Flush – 1.28 gal (4.8 L)
• Flushometer Valve Type Effective Dual Flush – 1.28 gal (4.8 L) The standard provides sig-
• Tank-Type Single Flush – 1.28 gal (4.8 L)
and WaterSense-Certified nificant water savings over
Effective Dual Flush – 1.28 gal (4.8 L)
and WaterSense-Certified current codes and addresses
Urinals 0.5 gal (1.9 L)
the unnecessary water waste
Faucets
• Public Lavatory 0.5 gpm (1.9 L/min) that takes place in buildings
• Public Metering Self-Closing 0.25 gal (1.0 L) per Metering Cycle
• Residential Bathroom Lavatory Sink 1.5 gpm (5.7 L/min) and WaterSense-Certified and on landscape, and es-
• Residential Kitchen 2.2 gpm (8.3 L/min)
Showerheads tablishes significant yet at-
• Residential 2.0 gpm (7.6 L/min) tainable limits to monitor and
• Residential Shower Compar tment All Shower Outlets – 2.0 gpm (7.6 L/min)
(Stall) in Dwelling Units and Guestrooms manage water consumption.
Table 1 Plumbing fixtures and fittings requirements.
Mandatory Site Water Use irrigation that use evapotranspiration,
Reduction soil types, weather data or on-site rain or are prohibited. In these prohibited
Landscape design has a huge impact moisture sensors can fix this problem. systems, water is withdrawn directly
on water use. To conserve resources, They will shut down the system when from the source water body, diverted
municipalities and other local water there is enough water available to the through a condenser where it absorbs
utilities have started to impose restric- root zone of the plants. Another require- heat, and then discharged back into the
tions on the use of domestic treated ment to reduce water use in landscaping source water body at elevated tempera-
(tap or potable) water for lawns and is through use of zoning the irrigation tures. Because once-through cooling
other landscape areas. From an eco- system. By placing plants in groups systems do not recirculate the cooling
nomic standpoint, the water that is near each other that require similar water, they can require thousands of gal-
available is becoming more expensive moisture levels, they can be similarly lons of water per day. Even though these
to water users than in the past. When irrigated, a practice known as hydrozon- systems can be simple and low-cost,
extensive landscaping is in turfgrass, ing, since differing amounts of water the environmental impact of drawing
water needs are the highest. Standard are required by trees, shrubs and grass. water from wells, lakes, streams, rivers
189.1 requires that at least 60% of the or even municipal water systems is high.
improved landscape of a project be in Mandatory Building High discharge temperatures back into
biodiversity plantings of native and Water Use Reduction the environment can have damaging
adapted plants, limiting the allowed The U.S. Green Building Council’s impacts, such as increased algae growth,
areas for turfgrass. These are plants that LEED rating system encourages use of depleted oxygen levels and elimination
reliably grow well in a given habitat with plumbing fixtures that are more efficient of microorganisms that feed fish.
minimal attention from humans in the than the EPAct 1992 code requirements Condensate from steam systems
form of winter protection, pest protec- and, in some cases, are WaterSense and large air-conditioning units (larger
tion, water irrigation, or fertilization certified. These high-efficiency goals than 65,000 Btu/h [19 000 W]) must
once root systems are established in the are part of the mandatory requirements be recovered and reused. Air handler
soil. Adapted plants are considered to of Standard 189.1 (Table 1). Appli- condensate recovery systems can reroute
be low maintenance but not invasive. ances must be ENERGY STAR rated. the collected condensate from the
Have you ever noticed sprinklers The standard also contains water effi- AHUs to cooling towers to be used as
watering grass when it is raining? The ciency requirements for HVAC equip- makeup water, reducing the amount
required use of smart controllers for ment. “Once-through” cooling systems of potable water needed for cooling
June 2010 ASHRAE Journal’s Guide to Standard 189.1 S17
18. tower processes. The recovered condensate
Subsystem Submetering Threshold
could also be used for landscape irrigation.
Cooling Towers (Meter On Makeup Cooling Tower Flow Through
Water use in cooling towers and evapora- Water and Blowdown) Tower >500 gpm (30 L/s)
tive cooling must be evaluated. Conductivity
Evaporative Coolers Makeup Water >0.6 gpm (0.04 L/s)
controllers and overflow alarms are required
in cooling towers with a flow rate greater than Steam and Hot Water Boilers >500,000 Btu/h (50 kW) Input
500 gpm (32 L/s) and evaporative coolers with Total Irrigated Landscape
>25,000 ft2 (2500 m2)
makeup water flow greater than 0.6 gpm (0.4 Area With Controllers
L/s). In addition, drift eliminators that achieve Separate Campus or Project Buildings Consumption >1,000 gal/day (3800 L/day)
drift reduction to a maximum of 0.002% of
the recirculated water volume for counterflow Separately Leased or Rental Space Consumption >1,000 gal/day (3800 L/day)
towers and 0.005% of the recirculated water Any Large Water-Using Process Consumption >1,000 gal/day (3800 L/day)
flow for cross-flow towers must be implemented.
Table 2 Water consumption monitoring thresholds.
Some buildings use potable water sprayed
on the roof to provide thermal condition-
ing. Although the use of roof ponds, roof spray and wetted ments, it has the option of demonstrating water savings via
gunny-bag systems can reduce the temperature of the roof a performance-based calculation, which is covered later.
and the heat load in a building, this is not a good use for
drinking water and is prohibited by Standard 189.1. Po- Prescriptive Site Water Use Reduction
table water can be used on a roof to establish a vegetated For landscaping site water use, a maximum of one-third of
or green roof, but after the landscape has been established the improved landscape area is allowed to be irrigated with
(no more than 18 months), the potable water irrigation potable water. The remainder of the improved landscape area
system must be removed or permanently disabled. must be designed with drought-tolerant plants that do not
require irrigation or are irrigated with water from an alterna-
Mandatory Water Consumption Measurement tive water source. Facilities with large areas of turfgrass in
The ongoing measurement of water consumption is their design, such as golf courses and driving ranges, must use
critical to the management of a building or campus and only municipally reclaimed water or another alternate on-site
the consumption of resources. The requirements for mea- source of water (such as on-site treated wastewater, captured
suring and monitoring water use is primarily to identify rainwater, cooling condensate, or groundwater pumped for
water use anomalies that might occur when building and purposes of dewatering foundations). Potable water or other
process systems break down. When connected to a real-time groundwater sources may not be used for irrigating these areas.
building management system, such events can be quickly When a landscape is initially installed, irrigation often is need-
addressed and corrected. Therefore, it is critical for build- ed to establish the vegetation. For a period of 18 months from
ing operators to measure and track the water consumption initial installation, potable water may be used for irrigation. Once
in their projects to ensure satisfactory performance during that period ends, the temporary irrigation system must be re-
operation. All projects are required to install measure- moved or permanently disabled. However, the amount of potable
ment devices with remote communication capability. water used during the landscape establishment period may not ex-
Both potable and reclaimed water entering the building ceed 70% of evapotranspiration rate (ETo) for turfgrass and 55%
project must be monitored or submetered (Table 2). Although it of ETo for other species. ETo values can be found in regional ag-
is important for projects to install measurement equipment on ricultural data for the project’s jurisdiction. Reclaimed water is re-
various water end uses, it is equally important for the resulting quired to be used during the landscape establishment period if it
data and use trends to be collected and evaluated by building is available at a water main within 200 ft (61 m) of the project site.
management. Consistent water use data informs manage-
ment staff of typical use patterns and alerts them to any leaks Prescriptive Building Water Use Reduction
or problems that may have arisen in the project. Monitoring Water use in cooling towers and evaporative cooling is a key
systems must be capable of recording and electronically storing concern. The water that is evaporated from a cooling tower is
the collected data on an hourly, daily and monthly basis and pure; that is, it doesn’t contain any of the mineral solids that
must be equipped to alert operators to problems in real time. are dissolved in the cooling water. Evaporation has the effect
of concentrating these dissolved minerals in the remainder
Prescriptive Option of the tower water. As water flows through a cooling tower
The prescriptive pathway outlines a series of additional system, the water becomes more concentrated with the miner-
specific water-saving strategies, building upon the manda- als remaining when water is evaporated. As a result, these
tory requirements detailed in the previous sections. If the systems require continuous blow down or “bleed off” with
project cannot, for any reason, meet the prescriptive require- added makeup water to maintain an acceptable concentra-
S18 ASHRAE Journal’s Guide to Standard 189.1 ashrae.org June 2010
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20. tion of minerals (measured as total dissolved solids). Dis- are required to have a leak detection system and a makeup
solved minerals (most commonly calcium and magnesium water meter so that building managers are made aware of
salts) can precipitate as an insoluble scale or sludge. any repairs that need to be made. An exception to the water
One indicator of cooling tower efficiency is cycles of con- features requirements exists for those building projects wish-
centration (COC), or concentration ratio. This is the ratio of ing to include an ornamental fountain, but which are not
the makeup water rate to the blowdown rate. While COC is located near a municipally reclaimed water source. Under this
an important factor in determining the ultimate water use of a exception, potable water may be used as makeup water for
cooling tower, it is also closely linked with the chemical treat- features with less than a 10,000 gallon (38 000 L) capacity.
ment regimen. Higher COC save water because the water stays Unlike ornamental water features, pools and spas are
in the system longer. However, in some cases, this also increases not required to use reclaimed water for health reasons.
requirements for chemical treatment. Lower COC result in However, they must be designed to either reuse treated
higher water use but generally also make water treatment sim- backwash water on landscaping or other applications, or
pler. As a result, the minimum COC required in this standard to reuse backwash water within the pool/spa system.
to conserve water are directly tied to makeup water quality.
In places with softer makeup water (less than 200 ppm or Performance Option
200 mg/L of total hardness expressed as calcium carbonate), The intent of the performance option is to provide an alter-
the cooling tower must be set to achieve a minimum of 5.0 native approach, wherein the project must exhibit overall water
COC. In areas with harder water (greater than 200 ppm or use reduction for projects that, for whatever reason, cannot—or
200 mg/L of total hardness expressed as calcium carbonate), will not—comply with the prescriptive methods. Projects can
a minimum of 3.5 COC is required. Implementation of a demonstrate compliance by completing performance-based
comprehensive water treatment system (sometimes using acid calculations for either site or building water use, or both.
treatment) is one strategy for compliance with the standard.
It is important to consider the pH/alkalinity associated with Performance Site Water Use Reduction
increased cycles of concentration. Standard galvanic protec- To demonstrate compliance with the performance op-
tion may be susceptible to “white rust” associated with higher tion it is necessary for the potable water use for landscaping
pH levels. The requirements of the standard can be waived to be less than 35% of the water demand for the landscape.
only in cases where the discharge water exceeds 1,500 ppm This means that a baseline water demand for the improved
(1,500 mg/L), or the silica exceeds 150 ppm (150 mg/L) landscape area of the project, based on evapotranspiration
measured as silicon dioxide before the COC are reached. rates for the applicable climatic area must be determined.
Commercial food service operations are one of the larger
users of water within the commercial sector. As such, the Performance Building Water Use Reduction
standard incorporates provisions addressing some of the Projects that want to complete a performance calcula-
water-using food preparation and dishwashing operations tion must demonstrate that by using the specified build-
in a typical food service facility. The specialized equipment ing and tenant equipment, together with expected oc-
available today for modern commercial kitchens uses much cupant type, the building’s water use will equal to or less
less water than their predecessors of the 1990s. The standard than the requirements for water use that otherwise would
encourages the installation of the most efficient equipment have been achieved through the prescriptive approach.
by establishing maximum water use thresholds that do not Based on the building and tenant equipment in the
compromise health, sanitary or culinary requirements. The building, project proponents must calculate expected wa-
types of equipment addressed by this standard include pre-rinse ter use if simply complying with the prescriptive measures,
spray valves, commercial dishwashers, food steamers, combina- and then compare that water use with the building as pro-
tion ovens, air-cooled ice machines and faucet controllers. posed. A successful performance calculation should dem-
Medical facilities such as hospitals, clinics, medical centers, onstrate that the building is using an amount of water that
and physician and dental offices are large water users as well. is equal to or less than the amount of water it would have
Specific requirements are applied to the following types of used had it adhered to the prescriptive requirements.
equipment and processes: steam sterilizers, large-frame x-ray film
processing equipment, digital imaging of radiography systems, Conclusion
hood scrubbers, vacuum pumps, and water treatment processes, Rapidly growing concerns regarding the impacts of water
including filtration processes, ion exchange and softening stress and scarcity have driven the need for an increased
processes, and reverse osmosis and nanofiltration equipment. focus on water use in, on and around buildings. Building
Ornamental fountains and features are acceptable within designers must recognize the impact their design decisions
a high-performance project, however, they must be supplied have on future generations. Professionals in the build-
with reclaimed water or another nonpotable source, and must ing industry must incorporate responsible water use ef-
be designed to reuse the water in the system. Water fountains ficiencies and strategies into the built environment.
S20 ASHRAE Journal’s Guide to Standard 189.1 ashrae.org June 2010
22. ASHRAE Journal’s
Guide to Standard 189.1
Energy Efficiency:
Building on Standard 90.1
By Stephen D. Kennedy, Member ASHRAE; Martha G. VanGeem, P.E., Member ASHRAE; Tom Lawrence, Ph.D.,
P.E., Member ASHRAE; Richard Lord, Member ASHRAE
E
nergy Efficiency, Section 7, either a prescriptive set of requirements zones across the U.S. Unless specifically
addresses six major catego- or a performance path to demonstrate exempted or otherwise addressed in the
ries: envelope requirements, full compliance with the energy chapter. energy efficiency section, the building
The energy requirements in Stan- project must meet all of the require-
on-site renewable energy systems,
dard 189.1 build upon those in Stan- ments of the Standard 90.1 Chapters 5
mechanical equipment efficiencies, dard 90.1. During the development through 10 (building envelope, HVAC,
energy consumption data collection, of Standard 189.1, a general goal was
peak load control and lighting. Each determined of setting design require- About the Authors
of these areas has been identified ments that would result in an overall Stephen D. Kennedy is territorial affairs
as a critical component in address- average of 30% energy use savings manager at Georgia Power Company in Atlanta.
compared to Standard 90.1-2007. Based Martha G. VanGeem, P.E., is a principal en-
ing the efficient use of energy in the
on energy modeling results by the gineer, Building Science and Sustainability, at
design of high-performance buildings. National Renewable Energy Lab and CTLGroup, Skokie, Ill. Tom Lawrence, Ph.D.,
P.E., is public service associate, Faculty of
The energy requirements include a set the U.S. Department of Energy, this Engineering, University of Georgia, in Athens,
of mandatory requirements that must goal was achieved based on an overall Ga. Richard Lord is Carrier fellow at United
be met for all projects, and the choice of average of building stock and climate Technologies Carrier Corp. in Murfreesboro, Tenn.
S22 ASHRAE Journal’s Guide to Standard 189.1 ashrae.org June 2010
23. ASHRAE Journal’s
Guide to Standard 189.1
Section 7:
Energy
Figure 1 U.S. climate zone map.
Efficiency
Dry (B) Moist (A)
Marine (C)
Unless specifically exempted
or otherwise addressed in the
energy efficiency section, the
building project must meet
all of the requirements of
Warm-Humid the Standard 90.1. In gen-
Below White Line
All of Alaska in Zone 7 except for eral, Standard 189.1 provides
the following boroughs in Zone 8:
Bethel Northwest Arctic requirements that are more
Dellingham Southeast Fairbanks Zone 1 includes:
Fairbanks N. Star Wade Hampton Hawaii, Guam, Puerto Rico stringent than Standard 90.1.
Nome Yukon-Koyukuk and the Virgin Islands
North Slope
service water heating, power, lighting, Energy Design Guide for Small Retail
and motors). In general, Standard Buildings, provided that those criteria
189.1 provides requirements that are were more stringent than the require-
more stringent than Standard 90.1. ments in Standard 90.1-2007. Where Materials. Using individual
the criteria in Standard 90.1-2007 were materials that have an air perme-
Prescriptive Envelope Requirements equal or more stringent, the require- ability not to exceed 0.004 cfm/ft 2
Insulation and Fenestration ment for Standard 189.1 was raised under a pressure differential of 0.3
The prescriptive building envelope by an increment with a few excep- in. water (1.57 lb/ft2) (0.02 L/s·m2
requirements in Standard 189.1 include tions in some milder climate zones. under a pressure differential of 75
additional energy-saving measures to For residential spaces, where the Pa). The requirement can be met
those in Standard 90.1. The thermal criteria are the same as those for non- using the list of the materials pro-
insulation requirements for opaque residential spaces in Standard 90.1, they vided in Appendix B of the stan-
assemblies, as well as the U-factor and are the same in Standard 189.1. Where dard or by testing other materials.
solar heat gain coefficient (SHGC) the residential criteria are more strin- Assemblies. Using assemblies of mate-
fenestration requirements for Stan- gent than the nonresidential criteria in rials and components that have an aver-
dard 189.1 are presented in Appendix Standard 90.1-2007, they have also been age air leakage not to exceed 0.04 cfm/ft2
A using the same format as those for made more stringent in Standard 189.1. under a pressure differential of 0.3 in. wa-
Standard 90.1. These criteria vary The prescriptive requirements can ter (1.57 lb/ft2) (0.2 L/s·m2 under a pres-
by climate zone (Figure 1), and these only be used when vertical fenestra- sure differential of 75 Pa). The require-
are the same climate zones used in tion is less than 40% of gross wall ment can be met using the list of the
Standard 90.1 and the International area. When using greater amounts assemblies provided in Appendix B of the
Energy Conservation Code (IECC). of vertical fenestration, the energy standard or by testing other assemblies.
For nonresidential spaces, the performance path in Section 7.5 of Building. Testing the completed
building envelope criteria are gener- the standard must be used. building and demonstrating that the
ally based on the most stringent of air leakage rate of the building en-
the criteria in E-Benchmark 1.1 (now Continuous Air Barrier velope does not exceed 0.4 cfm/ft2
Core Performance as of July 2007) and The prescriptive requirement for under a pressure differential of 0.3 in.
the Advanced Energy Design Guide for a continuous air barrier can be met water (1.57 lb/ft2) (2.0 L/s·m2 under
Small Office Buildings and the Advanced using any one of three criteria: a pressure differential of 75 Pa).
June 2010 ASHRAE Journal’s Guide to Standard 189.1 S23
24. Note that the requirement for assemblies is 10 times Photo 1 Overhang on west face of building in Climate Zone 5
more stringent than for whole buildings. This is because (photo courtesy of CTLGroup).
of the added air leakage that occurs due to penetrations
and gaps that occur when whole buildings are tested com-
pared to individual assemblies. Similarly, the requirement
for materials is 10 times more stringent than that for as-
semblies because of the air leakage that occurs when ma-
terials are taped or pieced together to form assemblies.
Fenestration Shading
The standard requires that there be permanent shading
projections on the west, south, and east walls of buildings
in Climate Zones 1 through 5 unless the vertical fenes-
tration receives direct solar radiation for fewer than 250
hours per year because of shading by nearby structures or
topography. This requirement is intended to reduce the
solar heat gain to the buildings in these climate zones.
Since the requirement is for an area-weighted projec-
tion factor of 0.5, not every window is required to have Figure 2 U.S. photovoltaic solar resource map: Flat plate tilted
a permanent shading projection or overhang. Require- at latitude. (NREL: www.nrel.gov/gis/solar.html.)
ments also can be met by recessed windows, the use of
balconies, building shapes that shade themselves or other
architectural features. A projection on the west face of
a building in Climate Zone 5 is shown in Photo 1.
Building and Fenestration Orientation
The prescriptive fenestration orientation requirement
for Climate Zones 1 through 6 encourages design that
orients the building with the longest façades on the north
and south. This discourages large amounts of fenestration
on the east and west facades, which are subject to the most
solar gains in the summer months due to the lower angle of
the sun on these faces. Lower SHGCs on the east and west
façades can be used to meet these requirements in Climate
Zones 1 through 4. A similar requirement is in place for
Climate Zones 5 and 6, but only restricts fenestration on
the west face. This recognizes the benefits of solar gains on
the east façade for morning warm-up in colder climates. for solar collectors, pathways for conduit, piping and as-
sociated equipment on the construction documents.
On-site Renewable Energy This minimum requirement was based on the assumption
The project committee recognized that today, renewable that a typical photovoltaic array generates 8 to 10 watts of
energy systems are not always cost effective. However, the power per square foot of photovoltaic panel when operating
committee also realized that once a building is constructed, at peak capacity and that roofs on most building can allocate
the opportunity for future installation of such systems is 50% of their roof area for these systems. The only exception
often lost forever. Meanwhile, the capital cost for such for the installation of such systems is if the building is in a
systems is expected to decline as their use increases. location with poor incident solar radiation, defined as 4 kW/
To enable the future installation of such systems as they m2·day on a collector oriented due south and tilted at an
become more cost effective, the standard has a manda- angle equal to the site’s latitude and as illustrated in Figure 2.
tory requirement that the building design provide for This exempts the upper Midwest and New England states, as
the future installation of a photovoltaic, solar thermal, well as portions of the Pacific Northwest. Sites with adequate
geothermal energy (but not including ground-source heat permanent shade also will often meet the exemption.
pumps) or wind system with a minimum rating of 13 Btu/h. Under the prescriptive requirements, buildings that do
ft2 (3.7 W/ft2) multiplied by the total roof area. Provi- not qualify for the same incident solar radiation exception
sion for future installation means to show allocated space must install on-site renewable energy systems at the time of
S24 ASHRAE Journal’s Guide to Standard 189.1 ashrae.org June 2010
26. construction. These systems must be
Figure 3 Complying with the HVAC equipment minimum efficiency requirements.
capable of providing annually at least ei-
ther 4 or 6 kBtu/ft2 (45 to 68 MJ/m2)of EPAct Baseline Higher Efficiency
conditioned space, depending on other Use equipment with EPAct baseline efficiency Use higher efficiency of ENERGY STAR require-
criteria that are used for compliance. levels, and: ments and Appendix C, and:
Since this requirement is in terms of • Renewable energy system producing 6.0 • Renewable energy system producing 4.0
kBtu/ft2 conditioned floor space annually kBtu/ft2 conditioned floor space annually
conditioned space rather than roof area, • Peak electrical load reduction of 10% • Peak electrical load reduction of 5%
compliance will be easier for low-rise
buildings or buildings with surrounding
space that can be used for on-site renew- Figure 4 Air economizer HVAC cooling energy savings.
able energy systems. Sites that meet the
poor incident solar radiation exception 8 – Fairbanks 81.6%
must purchase a specified amount of 7 – Duluth 72.1%
renewable energy complying with the 6B – Helena 66.5%
Green-e Energy National Standard for 6A – Burlington 53.7%
5C – Vancouver 81.2%
Renewable Electricity Products. This
5B – Boise 58.8%
requirement corresponds to a purchase
5A – Chicago 24.5%
of renewable energy certificates (RECs) 4C – Salem 65.1%
for about 10 years. When these pre- 4B – Albuquerque 54.4%
scriptive requirements are not met, the 4A – Baltimore 42.9%
energy performance path in Section 3C – San Francisco 80.4%
7.5 of the standard must be used. 3B – El Paso 40%
3A – Memphis 29%
2B – Phoenix 25.5%
Mechanical Equipment
0% 10% 20% 30% 40% 50% 60% 70% 80% 90%
The minimum mechanical equip-
Percent Savings Versus No Economizer
ment efficiencies are those required
by the National Appliance Energy
Conservation Act (NAECA), the En- STAR requirements and the require- control with the first stage relying on the
ergy Policy Act (EPACT), and the ments in Appendix C of Standard 189.1. economizer and the second stage adding
Energy Independence and Security Act There are also lower occupant density the mechanical cooling. It also requires
(EISA). As a high performance green thresholds associated with demand integrated economizers for all econo-
building standard, Standard 189.1 control ventilation requirements and mized units such that the economizer
seeks to encourage the installation increased duct sealing requirements. and mechanical cooling can be used
of higher than minimum efficien- To avoid providing outside ventila- together. For most systems with cooling
cies not only in mechanical equip- tion air to a space during periods of capacity exceeding 33,000 Btu/h (9671
ment but throughout the standard. less than design occupancy, demand W), either an air or water economizer is
The requirements for mechanical control ventilation is required except required except in certain circumstances
equipment are based on Section 6 of in certain cases. Not only does this (for example, Climate Zones 1A, 1B
Standard 90.1 except as modified. In result in additional energy savings, but and 2A). The changeover control for
the case of mechanical equipment for this may help avoid mold and other economizers must be either differential
HVAC, two options exist for compliance excess moisture problems that occur, enthalpy or differential dry bulb.
within the prescriptive compliance path resulting in a healthier environment, To reduce the energy waste associated
(Figure 3). The first option is to comply as well as a more efficient building. with simultaneous operation of heating
with the energy-efficiency requirements With the increased envelope require- and cooling equipment, zone controls
of the NAECA, EPACT and EISA, ments and higher internal commercial are required. These controls are intend-
which are the values listed in Standard building loads, the use of air and water ed to prevent reheating, recooling and
90.1 and the renewable energy and peak economizers for free cooling can offer the mixing or simultaneous supply of air
load reduction provisions as outlined in significant energy savings for a typical that has been previously heated with air
the prescriptive sections. The second op- office building. Standard 189.1 modi- that has been previously cooled either by
tion allows a reduction by one-third in fies the minimum size requirements for mechanical systems or by an economiz-
the amount of on-site renewable energy economizers from those of Standard er. Limited simultaneous heating and
required and a less stringent peak load 90.1 and requires rooftop units with a cooling of air is allowed, based on the
reduction if mechanical equipment effi- capacity of less than 60,000 Btu/h (17 larger of the design outdoor airflow rate or
ciencies are increased to meet ENERGY 584 W) to have two stages of capacity 15% of the supply airflow to the zone.
S26 ASHRAE Journal’s Guide to Standard 189.1 ashrae.org June 2010
27. Indoor fan power in commercial a function of the region, supply air and retained. For energy sources meet-
buildings can be a significant por- volume and outside air volume. ing certain size or capacity thresholds,
tion of the overall HVAC energy To reduce energy in unoccupied Standard 189.1 requires that measure-
use due to ventilation requirements hotels and motel guest rooms, controls ment devices with remote communica-
that require the fan to operate con- must be installed that set back the tion capability be installed to collect
tinuously. Standard 189.1 has reduced HVAC system and turn off plug loads energy consumption data. If building
maximum allowable fan power by 10% when the rooms are unoccupied. Plug energy metering is required for an
versus Standard 90.1. It also requires loads, including lighting, switched energy source, then energy subsystems
all constant volume DX units with a outlets, and television, must be turned such as the total HVAC system, people
capacity greater than 110,000 Btu/h off when occupants are not in the moving system and so on, are also
(32 238 W) and all fan coils with a room. In Europe and Asia this is often required to collect and electronically
motor horsepower greater than 5 hp accomplished by inserting a room key store data if the subsystems’ collective
(3.7 kW) to have at least a two-speed card in a device that activates power to load exceeds specified thresholds.
fan or variable speed fan to allow for these items when entering the room. The data storage system must also be
reductions in fan power at lower loads. capable of producing reports summariz-
Standard 189.1 also expands the Energy Consumption Data Collection ing the data so that building perfor-
requirements for exhaust air energy An important part of ensuring the mance can be assessed at least monthly.
recovery devices to be used to transfer sustainable performance of an energy- For example, if the natural gas service
energy from the exhaust air to the efficient building is establishing that it to the building exceeds the equivalent
return air in heating and from the continues to perform as designed. To of 1,000,000 Btu/h (293 kW), then the
outdoor ventilation air to the exhaust better facilitate that performance, energy natural gas service must be metered and
air in cooling. The requirements are consumption data must be captured data retained. Gas subsystems such as
www.info.hotims.com/30916-62
June 2010 ASHRAE Journal’s Guide to Standard 189.1 S27
