UC Santa Barbara
UC Santa Barbara Previously Published Works
Title
Environmental performance of green building code and certification systems.
Permalink
https://escholarship.org/uc/item/1wv6m7hr
Journal
Environmental science & technology, 48(5)
ISSN
0013-936X
Authors
Suh, Sangwon
Tomar, Shivira
Leighton, Matthew
et al.
Publication Date
2014
DOI
10.1021/es4040792
Peer reviewed
eScholarship.org Powered by the California Digital Library
University of California
Environmental Performance of Green Building Code and Certification
Systems
Sangwon Suh,*
,†,‡
Shivira Tomar,
‡
Matthew Leighton,
‡
and Joshua Kneifel
§
†
Bren School of Environmental Science and Management, University of California, Santa Barbara, California 93106-5131, United
States
‡
IERS, 5951 Encina Road, Suite 206, Goleta, California 93117, United States
§
Applied Economics Office, Engineering Laboratory, National Institute of Standards and Technology (NIST), 100 Bureau Drive Stop
8603, Gaithersburg, Maryland 20899, United States
*
S
Supporting Information
ABSTRACT: We examined the potential life-cycle environmental
impact reduction of three green building code and certification
(GBCC) systems: LEED, ASHRAE 189.1, and IgCC. A recently
completed whole-building life cycle assessment (LCA) database of
NIST was applied to a prototype building model specification by
NREL. TRACI 2.0 of EPA was used for life cycle impact
assessment (LCIA). The results showed that the baseline building
model generates about 18 thousand metric tons CO
2
-equiv. of
greenhouse gases (GHGs) and consumes 6 terajoule (TJ) of
primary energy and 328 million liter of water over its life-cycle.
Overall, GBCC-compliant building models generated 0% to 25%
less environmental impacts than the baseline case (average 14%
reduction). The largest reductions were associated with acid-
ification (25%), human healthrespiratory (24%), and global
warming (GW) (22%), while no reductions were observed for ozone layer depletion (OD) and land use (LU). The
performances of the three GBCC-compliant building models measured in life-cycle impact reduction were comparable. A
sensitivity analysis showed that the comparative results were reasonably robust, although some results were relatively sensitive to
the behavioral parameters, including employee transportation and purchased electricity during the occupancy phase (average
sensitivity coefficients 0.26−0.29).
■
INTRODUCTION
Buildings generate substantial environmental and natural-
resource impacts on modern society. Estimates show that
about 40 exajoules (EJ) or 40% of total energy consumed in the
US is associated with residential and commercial buildings.
1−3
Given the importance of energy consumption in climate
change, acidi fication, tropospheric oxidant formation, and toxic
impacts, the significance of buildings in many air-pollutant-
induced impacts is obvious. In addition, buildings are an
important conduit for water consumption, land conversion, and
land occupation,
1
and building materials constitute the most
significant end-use category of material consumption by mass.
4
Various approaches including, but not limited to, material
choices,
5,6
thermal insulation,
7,8
local sourcing,
9
passive thermal
storage and alternative envelope designs,
10−13
and energy
efficient designs
14−16
have been developed and applied in an
attempt to reduce environmental and resources footprints of
buildings. Since the 1990s, lessons learned from such efforts
have informed industry standards, model building codes, rating
systems, and green building certifications,
14,17,18
which are
collectively referred to as green building code and certification
(GBCC) systems in this paper.
Over a dozen GBCC systems and their combinations are
reported in the literature,
19−24
among which some of the most
frequently discussed include LEED (Leadership in Energy and
Environmental Design), BREEAM (Building Research Estab-
lishment’s Environmental Assessment Method), Green Globes,
Living Building Challenge (LBC), ISO/TS 21929-1:2006,
ASHRAE (American Society of Heating, Refrigeration, and
Air-Conditioning Engineer s) 189.1 and 90.1, and IgCC
(International Green Construction Code). Some of these
GBCC systems have achieved remarkable market penetration
over the past decade. For example, according to the U.S. Green
Building Council (USGBC), as of August 2013 there are 44,270
LEED-certified projects in the U.S. alone.
25
A natural question is whether these GBCC systems mitigate
environmental impacts. If so, which environmental impacts are
better addressed, and how much impact can they mitigate?
Received: October 17, 2013
Revised: January 13, 2014
Accepted: January 31, 2014
Published: January 31, 2014
Policy Analysis
pubs.acs.org/est
© 2014 American Chemical Society 2551 dx.doi.org/10.1021/es4040792 | Environ. Sci. Technol. 2014, 48, 2551−2560
Empirical studies that attempt to answer such questions
focus mainly on direct energy and water consumption.
24,26−28
Many such studies show modest to significant benefits of
GBCC systems but not without exceptions. For example,
Turner and Franckel (2008)
26
concluded that LEED-certified
buildings use 26−44% less energy than average buildings
reported in the Commercial Buildings Energy Consumption
Survey (CBECS).
29
Newsham et al. (2009)
30
confirmed that
LEED-certified buildings use less energy on average but also
showed that 28−35% of LEED-certified buildings use more
energy than non-LEED-certified counterparts. Scofield
(2009)
28
re-examined Newsham’s analysis and came to the
conclusion that there is no evidence that LEED-certified
buildings collectively show lower energy consumption than
comparable non-LEED buildings. These empirical analyses
frequently use cross-sectional data from the Commercial
Buildings Energy Consumption Survey (CBECS)
29
of the
U.S. Energy Information Administration (EIA) to derive energy
and water consumption profiles of comparable buildings. One
of the challenges, which in part contributed to the mixed results
in the literature, lies in the difficulties of establishing
counterfactuals: each building is, to a certain extent, unique
with respect to the design, materials, location, climate, purpose,
and occupants, which in concert influence the building’s energy
and water consumption profiles.
A few studies approached the question using life cycle
assessment (LCA) and went beyond direct energy and water
consumption. In their pioneering work on an earlier version of
LEED, Scheuer and Keoleian (2002)
31
applied LCA and
showed that the lack of comparability between LEED credits
creates disparities in quantitative environmental outcomes
across buildings with the same level of LEED rating. Humbert
et al. (2007)
32
quantified life-cycle environmental costs and
benefits of LEED credits and concluded that the life-cycle
environmental benefits of a LEED credit can be negative or
positive, the credit that provides the highest environmental
benefits being the requirement of at least 50% renewable
energy.
Building upon the previous studies, we attempt to approach
the question using a recently completed whole-building LCA
database of the National Institute of Standard and Technology
(NIST)
33
and a prototype model building specification by the
National Renewable Ene rgy Laboratory (NREL).
34
The
objective of our study is to quantify the potential life-cycle
environmental impact reduction of three GBCC systems:
LEED, ASHRAE 189.1, and IgCC, covering a wide range of
environmental impact categories. Our intention is neither to
generalize the environmental performance of the three GBCC
systems nor to provide a rank between them. Rather, we intend
to gauge the potentia l environmental benefits of GBCC
systems from a life-cycle point of view using a typical small
office building and the three GBCC systems as a case study.
■
METHOD AND DATA
In this study, we first mapped the criteria for compliance by the
three GBCC systems in terms of their potential influence,
either on inputs (e.g., material, services, energy, and water) or
on outputs (e.g., waste, greenhouse gas emissions, toxic
pollutant emissions). Using a prototypical small office building
model as a baseline,
34
we quantified inputs to and outputs from
each of the three GBCC-compliant building models. The inputs
and outputs quantified were used to generate life cycle
inventories (LCIs) for the baseline and the three GBCC-
compliant building models. Building lifetime was assumed to be
40 years following previous literature and data available for our
analysis.
35,36
We applied a life cycle impact assessment (LCIA)
model and interpreted the results. The overall procedure of our
analysis is illustrated in Figure 1.
The three GBCC systems selected in this study are briefly
reviewed in the next subsection. The analytical approach is
further elaborated in the next five subsections.
Scope of the GBCC Systems Analyzed. In this study we
selected three GBCC systems: LEED, ASHRAE 189.1, and
IgCC. These GBCC systems were chosen because they have
been widely adopted by local authorities and architects and
were developed in a close coordination, so that the topical areas
covered are closely aligned.
LEED is a voluntary, third-party, verified green building
rating and certification system led by the U.S. Green Building
Council.
37
LEED criteria are regularly updated through an
open, participatory process. The most recent, officially released
version of the LEED rating system is version 3 published in
2009. The next version is expected to be released later in 2013.
The remaining description of LEED is based on LEED version
3. LEED employs credit points as well as prerequisites, which
are mandatory for any level of LEED certification. Depending
on the type of project in question, LEED uses a point scale
ranging from 100 to 125, covering 5 major topical areas
including (a) sustainable sites; (b) water efficiency; (c) energy
and atmosphere; (d) materials and resources; and (e) indoor
environmental quality. In addition, up to 11 additional points
can be added in the areas of design innovations and regional
priorities.
LEED contains Global Alternative Compliance Paths
(ACPs) that allow project teams outside the U.S. to select
local equivalents to the prescribed U.S. codes and regulations
for select credits. The ACPs are substitute credit and
prerequisite requirements that establish a new and different
way to demonstrate compliance with the stated intent of a
Figure 1. Procedure for LCA of Green Building Standard, Code and
Certification Systems: (A) Key features matrix for LEED, ASHRAE
189.1 and IgCC; (B) Bill of Materials (BoM) for the baseline and
three alternative building models to conform three GBCC systems;
(C) Quantification of occupancy and postoccupancy inputs and
outputs; (D) Mapping the B oM and the occupancy and
postoccupancy inputs and outputs data with LCI databases; resulting
Life Cycle Inventory (LCI); (E) Application of TRACI 2.0 for impact
assessment; (F) Characterized impact results for interpretation and
sensitivity analysis.
Environmental Science & Technology Policy Analysis
dx.doi.org/10.1021/es4040792 | Environ. Sci. Technol. 2014, 48, 2551−25602552
credit or prerequisite. This is applicable only for certain credits
such as for credit 1, ‘water efficient landscaping’ under the
Water Efficiency requirement.
38
We used ‘certified’ level rating
for our analysis, which requires 40 or higher credit points.
ASHRAE 189.1 of 2009
39
is an ANSI (American National
Standards Institute) standard in a model code format that
intends to set the minimum requirements for the design of
high-performance green buildings. Model building codes are
designed to be applicable to a wide range of local governments
and municipalities, which help reduce redundant efforts to
develop them by individual entities. ASHRAE 189.1 was
developed jointly by the American Society of Heating,
Refrigeration, and Air-Conditioning Engineers (ASHR AE),
the Illumi nating Engineering Society (IES), and the US
Green Building Council (USGBC). ASHRAE 189.1 uses
ASHRAE 90.1
40
as the baseline case, targeting 30% additional
energy savings compared to the baseline.
41
ASHRAE 189.1
codes consist of mandatory provisions and prescript ive
recommendations over six topical areas, which correspond
well with those in LEED.
International Green Construction Code (IgCC)
42
is also
designed as a model building code by the International Code
Council (ICC). Local governments can adopt IgCC either as a
mandatory or voluntary requirement. IgCC recognizes
ASHRAE 189.1 as an alternative compliance path. The topical
areas that IgCC covers are similar to ASHRAE 189.1 and
LEED, with a notable exception on the commissioning,
operation, and maintenance sections. IgCC provides both
mandatory and elective provisions and al lows alternative
compliance paths on a number of specific requirements. For
instance, a whole-building LCA is recognized as an alternative
to material selection requirements (section 505). In this study,
we used the mandatory requirements as the basis of modeling
the effect of adopting IgCC to the baseline building model.
The three GBCC systems described in this section have been
developed in close consultation with each other, cover similar
topical areas, and in part employ comparable requirements.
Nevertheless, the three systems utilize different modalities of
implementation: LEED is a voluntary certification system based
on credit points, while ASHRAE 189.1 and IgCC are developed
as a model building code designed to be adopted as building
codes by local authorities, which set normative requirements.
As such, a direct comparison between them may not be
relevant. Instead, the close coordination between the three
GBCC systems and the participatory nature of their develop-
ment processes provide a point of reference to contemporary
GBCC systems, the potential implications to the environment
of which are examined in this study for the case of a small offi ce
building.
Key Feature Mapping. In this study we first mapped the
criteria for compliance with LEED (for ‘new office buildings’),
ASHRAE 189.1, and IgCC to a list of 15−30 key features for
each that affect the life-cycle environmental performance
through changes in the inputs (e.g., material, services, energy,
and water), outputs (e.g., waste, greenhouse gas emissions,
toxic pollutant emissions), or both (see Supporting Information
(SI) section 1).
First, we analyzed each criterion of the three GBCC systems
and determined whether implementing a criterion is likely to
affect the life-cycle environmental impacts quantified using
current LCA methodology and data available. For example,
ASHRAE 189.1’s section 5.3.3, IgCC’s clause 409, and LEED’s
SS 8 set exterior lighting specifications to reduce light pollution.
While light pollution is becoming an increasingly important
issue, the methodology to characterize the impact has yet to be
developed and incorporated in LCA. Therefore implementing
the requirement is unlikely to affect LCA results. On the other
hand, ASHRAE 189.1’s section 5.3.5, IgCC’s clause 407, and
LEED’s SS4.1, SS4.2, SS4.3, and SS4.4 set specifications to
reduce transportation needs, the impact of which can be easily
quantified using current LCA methodology (see section 1 of
the SI).
Second, the effects of implementing the criteria that are likely
to affect life-cycle environmental performance are quantified in
terms of the changes in inputs and outputs throughout the
preoccupancy, occupancy, and postoccupancy phases. For
ASHRAE 189.1 and IgCC, this was done by simply changing
the parameters of the baseline building model in accordance
with the requirements set by these two building codes. For
LEED, however, an architect can choose different combinations
of credits to achieve the same, certification-level compliance.
Therefore, we adjusted the parameters of the baseline building
model under three scenarios: (a) ASHRAE 189.1-comparable
case, (b) ‘LCA-relevant credits first’ case, and (c)
‘no LCA-
relevant credits’ case. Some local authorities recognize a
certification-level LEED rating as well as ASHRAE 189.1 and
IgCC as an alternative compliance path for their building codes,
and therefore, the ASHRAE 189.1-comparable case was set as a
default for the certification-level LEED case. Under the ‘LCA-
relevant credits first’ case, the credit points of which the
environmental benefits can be quantified using LCA were
incorporated as much as possible, while the ‘no LCA-relevant
credits’ case draws credit points from the requirements of
which the environmental benefits cannot be quantified by the
current LCA methodology. The allocation of LEED credit
points for these three scenarios is shown in Table 1.
As shown in Table 1, there were 38 credits, of which the
environmental benefits of implementation can be measured
using LCA, for the ‘LCA-relevant credits first’ case.
Table 1. Allocation of LEED Credit Points for ASHRAE
189.1-Comparable Case, Best Case, and Worse Case
Scenarios Used in This Study
LEED credits for
credit
‘no LCA-
relevant
credits’
case
ASHRAE-
compliant
case
‘LCA-
relevant
credits first’
case
measurable
using LCA
alternative
transportation -
public transportation
access
a
016
water use reduction
b
024
optimize energy
performance
c
01319
on-site renewable
energy
d
047
construction waste
management
e
012
unmeasurable using LCA (remaining
credits)
≥40 ≥19 ≥2
total (minimum 40 for certification-
level)
≥40 ≥40 ≥40
a
Sustainable Sites (SS Credit 4.1).
b
Water Efficiency (WE Credit 3).
c
Energy and Atmosphere (EA Credit 1).
d
Energy and Atmosphere
(EA Credit 2).
e
Materials and Resources (MR Credit 2).
Environmental Science & Technology Policy Analysis
dx.doi.org/10.1021/es4040792 | Environ. Sci. Technol. 2014, 48, 2551−25602553
Estimation of Bill of Materials (BoM). After the key
features of the three GBCC systems were analyzed, Bills of
Materials (BoM) for a baseline building model and those for
GBCC-compliant alterations to the baseline were developed.
We used the BoM for a 3-story office building (national
average) compiled by the National Institute of Standards and
Technology (NIST),
35,43−45
which is based on the specifica-
tions of the National Renewable Energy Laboratory (NREL)’s
ASHRAE 90.1-compliant prototype for a 3-story small office
building.
34
Table 2 lists the specifications for the NREL
prototype small office building.
The BoM data from NIST contains information on the cost
of inputs for a prototypical, 3-story office building in a
UNIFORMAT II third-level breakdown organized into 7
general categories: (i) Substructure, (ii) Shell, (iii) Interiors,
(iv) Services, (v) Equipment & Furnishings, (vi) Special
Construction, and (vii) Building Sitework.
36
For each general
category, a total cost is provided along with a list of assemblies
that contribute to the total costs. A building assembly may be
comprised of multiple components. For example, the assembly
category, ‘Spread Footings’ consists of wooden concrete forms,
steel reinforcements, and concrete. The building-assembly level
BoM was not granular enough for constructing an LCI and was
therefore further disaggregated into subcomponents using the
RSmeans database.
46
For example, the BoM data that NIST
provided shows $49,000 worth of input for the category,
“A1010 Standard Foundation”. RSMeans data allowed us to
further disaggregate the BoM, first to three assembly categories:
(1) “Strip footing, concrete, reinforced, load 11.1 KLF, soil
bearing capacity 6 KSF, 30.48 cm deep, 60.96 cm wide”, (2)
“Spread footings, 20,684 kPa concrete, load 200K, soil bearing
capacity 6 KSF, 1.82 m−0 square cm, 50.8 cm deep”, and (3)
“Spread footings, 20,684 kPa concrete, load 300K, soil bearing
capacity 6 KSF, 2.13 m−38.70 cm
2
, 63.5 cm deep”. These three
assembly level components were further disaggregated into 16
subassembly components, including “concrete form, plywood”,
“rebar, footings”, and “concrete, ready mix”.
The key features of each of the three GBCC systems were
then mapped into potential BoM changes needed to satisfy
each GBCC system. There can be a one-to-many correspond-
ence between a GBCC requirement and potential BoM changes
to satisfy the requirement. For example, the building envelope
section of the ASHRAE 189.1 specifies, for each climate zone,
energy efficiency requirements for building envelope compo-
nents including roof and wall. Such a requirement can be
achieved by (a) increasing the thickness of the materials for the
envelope specified in the baseline building model or by (b)
adding new materials. Given the wide variety of envelope
materials, there can be near infinite combinations of materials
that can achieve the same requirements. In this case, we used
two criteria to select one representative option for a BoM
change: (i) whether the option can be commonly and easily
applied to all three GBCC systems and (ii) whether the option
can be easily translated into quantifiable changes. For example,
improvements in the roof and wall thermal performance were
obtained by increasing the thickness of the insulation modeled
using EnergyPlus
47
software tool, because this option is
straightforward and can be easily applied to all GBCC systems.
In many cases, the level of change required in a BoM to
satisfy certain GBCC criteria needs to be calculated using
engineering estimations. For example, the baseline building
model following ASHRAE 90.1 requires the coefficient of
performance (COP) of packaged air conditioning systems of 19
kW to 70 kW capacity to be a minimum of 3.0, whereas
ASHRAE 189.1 requires a 3.7. In this case, we used the
regression model of Kneifel (2012),
35
which shows th e
relationship between an increase in HVAC efficiency and
percent increase in HVAC purchase cost, to estimate the
change in BoMs to meet the higher efficiency standard in air
conditioning systems of ASHRAE 189.1.
As a result, four BoMs were obtained, one for the baseline
building and three for the GBCC-compliant modi fications. We
further examined the completeness of these BoMs by
comparing them against the input structures of relevant
building sectors in the U.S. national input-output table by the
Bureau of Economic Analysis (BEA).
48
We identified a number
of missing inputs such as transportation and on-site fuel
consumption, which were estimated and incorporated into
respective BoMs.
Occupancy and Postoccupancy Phases. Occupancy and
postoccupancy phase materials, energy, water requirements, on-
site emissions, and end-of-life waste were estimated for each of
the four building models obtained in the previous step.
Occupancy Phase. For the occupancy phase, energy and
water consumption as well as occupants’ commuting,
maintenance, and repair were included in the scope. Data on
annual electricity and natural gas use for the prototype small
office building were generated using EnergyPlus
47
and NREL’s
OpenStudio software package.
49
Compliance to ASHRAE 189.1 and IgCC under ‘Energy’
category can be achieved either through prescriptive com-
pliance path or performance compliance path. The performance
option generally involves a model-based calculation and does
not specify specific improvements from the baseline. Therefore,
for the sake of simplicity in modeling energy reductions, the
prescriptive option was chosen for the ASHRAE 189.1 and
IgCC 2012.
The annual energy consumption of the office building will
vary depending on its geographic location and climate zone. To
account for this variability, the building energy simulations were
run 8 times, one for each of the major climate zones within the
U.S. following Baechler et al. (2010).
50
The representative cities
for each of the climate zones and the electricity and natural gas
consumption results are shown in SI section 2. Baseline energy
consumption results for each climate zone were combined into
Table 2. Prototype 3-Story Office Building Specifications
parameter specification
CBECS type office
% U.S. floor space 17%
number of floors 3
floor height 3.66 m
floor area 1858 m
2
roof type IEAD
wall type mass (masonry)
% glazing 20%
max occupancy 72 people or 1 person per 25.5 m
2
density 25.5 m
2
/occupant
lighting 8.6−14.0 W/m
2
elec. equipment load 8.07 W/m
2
cooling equipment rooftop packaged unit
heating equipment furnace
infiltration (ACH) 0.3 or 0.189 m
3
/s per floor
ventilation (ACH) 0.4 or 0.246 m
3
/s per floor
Environmental Science & Technology Policy Analysis
dx.doi.org/10.1021/es4040792 | Environ. Sci. Technol. 2014, 48, 2551−25602554
