Life-Cycle Assessment Modeling of Construction Processes
for Buildings
Melissa M. Bilec1; Robert J. Ries2; and H. Scott Matthews, A.M.ASCE3
Abstract: This research examined the environmental impacts due to the construction phase of commercial buildings. Previous building
research has often overlooked the construction phase and focused on the material and use phases, discounting the significant environmental impacts of construction. The research was conducted using life-cycle assessment 共LCA兲 methodology, which is a systematic
environmental management tool that holistically analyzes and assesses the environmental impacts of a product or process. Life-cycle
inventory results focused on particulate matter, global warming potential, SOx, NOx, CO, Pb, nonmethane volatile organic compounds,
energy usage, and solid and liquid wastes. Results over the entire building life cycle indicate that construction, while not as significant as
the use phase, is as important as other life-cycle stages. This research used augmented process-based hybrid LCA to model the construction phase; this modeling approach effectively combined process and input-output 共IO兲 LCA. One contribution was the development of a
hybrid LCA model for construction, which can be extended to other sectors, such as building products. Including IO results, especially
construction service sectors, is critical in construction LCA modeling. Results of a case study demonstrated that services had the highest
level of methane emissions and were a significant contributor to CO2 emissions.
DOI: 10.1061/共ASCE兲IS.1943-555X.0000022
CE Database subject headings: Construction; Life cycles; Environmental issues; Buildings, nonresidential.
Author keywords: Construction; Life cycle; Environmental issues.
Introduction
Research on environmental impact of buildings has primarily
focused on material manufacturing, energy use during building
operation, and waste management when decommissioning buildings. On-site construction is often overlooked or incompletely
modeled, leading to a gap in understanding the full spectrum of
possible sources of environmental impacts from the life cycle of
the built environment. Construction activities have an impact on
air quality recently exemplified by China’s restrictions on construction projects prior to and during the 2008 Beijing Olympics
in an effort to improve local air quality. When fully investigated,
on-site construction activities are found to have a range of significant impacts. Service sectors such as design 共e.g., architects and
engineers兲 and construction 共e.g., surveyors and construction
firms兲 represent a noteworthy but often ignored source of environmental impacts. The research used life-cycle assessment
共LCA兲, a systematic environmental management tool that holistically analyzes and assesses the environmental impacts of a prod-
uct or process. LCA can be used for decision making that
inherently promotes stewardship by considering global, national,
and regional impacts on social and environmental problems such
as human health, resource depletion, and ecosystem quality.
While LCA is a powerful tool, creating an accurate and inclusive
model is often difficult. LCA practitioners are often faced with
making difficult decisions related to selecting the appropriate
scope or boundary of the analysis, the sources of data for lifecycle inventories, software, and impact assessment methods. Hybrid LCA frameworks that combine input-output 共IO兲 and process
LCA modeling approaches are being explored to address some of
these issues. This work focused on hybrid LCA for the construction phase of a commercial building. The hybrid framework,
while developed for construction, can also be applied to analyze
the life cycle of other products or processes. This paper discusses
the motivation behind the research, provides a brief background
and literature review on LCA and construction, presents the
model development and its structure, examines a representative
case study, and concludes with recommendations for improving
the construction process and LCA modeling.
1
Assistant Professor, Dept. of Civil and Environmental Engineering,
Univ. of Pittsburgh, Pittsburgh, PA 15261 共corresponding author兲. E-mail:
mbilec@pitt.edu
2
Assistant Professor, Rinker School of Building Construction, Univ.
of Florida, Gainesville, FL. E-mail: rries@ufl.edu
3
Associate Professor, Civil and Environmental Engineering/
Engineering and Public Policy, Carnegie Mellon Univ. of Pittsburgh,
Pittsburgh, PA 15213. E-mail: hsm@cmu.edu
Note. This manuscript was submitted on April 14, 2009; approved on
September 16, 2009; published online on October 2, 2009. Discussion
period open until February 1, 2011; separate discussions must be submitted for individual papers. This paper is part of the Journal of Infrastructure Systems, Vol. 16, No. 3, September 1, 2010. ©ASCE, ISSN 10760342/2010/3-199–205/$25.00.
Motivation
The built environment contributes significantly to environmental
impacts regionally, nationally, and globally. All phases of a building’s life cycle—design, raw material extraction and processing,
manufacturing, construction, use and maintenance, and deconstruction—contribute to environmental impacts and energy use. A
fair amount of research has focused on the material phase and the
associated impacts from extraction and manufacturing. Some research has looked at end-of-life options for commercial buildings
共Guggemos and Horvath 2003兲. Existing research on the con-
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struction phase has assumed that the impacts are negligible 共Junnila and Horvath 2003兲, while others have indicated that the
environmental impacts associated with construction are underestimated 共Hendrickson and Horvath 2000兲.
LCA is an important method to determine and measure the
environmental performance of a product or process. Guidelines
for performing an LCA are delineated by International Organization for Standardization’s 共ISO兲 14040 series 关International Organization for Standardization 共ISO兲 2006兴. As defined by the ISO
14040 series, LCA is an iterative four-step process including goal
and scope definition, life-cycle inventory 共LCI兲 analysis, lifecycle impact assessment 共LCIA兲, and interpretation. LCI is often
where LCA studies terminate due to inconsistent framework, incomplete development, and subjectivity in the LCIA stage. Many
construction LCAs utilize either process-based 共Keoleian et al.
2000兲 or IO techniques 共Ochoa et al. 2002兲; another option is
hybrid LCA modeling, which is used in this research. This research combines the strengths of both techniques to develop a
framework for hybrid LCA modeling.
Background and Literature Review on LCA and
Construction
There are a limited number of published studies on LCA and
commercial buildings. Few of these studies comprehensively considered on-site construction processes with the exception of Junnila and Horvath 共2003兲, Hendrickson and Horvath 共2000兲, Ochoa
et al. 共2002兲, Guggemos and Horvath 共2005, 2006兲, Junnila et al.
共2006兲, and Sharrard et al. 共2008兲. Some studies stated that construction was included, but the definition of construction included
various stages of material extraction, production, and transportation and not on-site construction processes 共Horvath and Hendrickson 1998; Treloar et al. 2004; Treloar et al. 2000兲. In
summary, published research on LCA for the construction phase
is limited and a consensus on methodology or approaches has not
fully developed. Furthermore, a comparison between the relevant
studies is difficult because the description of the building lifecycle phases is not consistent. For example, Ochoa et al. 共2002兲
included raw material acquisition, manufacturing, and transportation to the construction site as the construction phase. Conversely,
Junnila and Horvath 共2003兲 considered the construction phase to
include on-site activities and transportation. Guggemos and Horvath 共2005, 2006兲 and Junnila et al. 共2006兲 developed model for
construction. The models created by Guggemos and Horvath
共2005, 2006兲 and Junnila et al. 共2006兲 include on-site energy,
equipment utilization, transportation, and temporary materials.
Athena Impact Estimator 4.0 includes primarily transportation
and equipment combustion 共Athena Institute 2008兲. This model
includes the aforementioned along with construction worker
transportation, construction service sectors, equipment manufacturing, and fugitive dust generation.
Model Development and Structure
The model includes both the LCI and impact assessment stages.
Process and IO methods are widely used and have strengths and
limitations. Process LCA models the known environmental inputs
and outputs by using a process flow diagram. Economic IO 共EIO兲
analysis, developed by Leontief 共1936兲, is an interdependency
model that quantifies proportional interrelationships among sectors in an economy. IO LCA combines national sector-by-sector
economic interaction data, which quantify the dependencies between sectors, with sector level environmental effects and resource use data 共Hendrickson et al. 1998; Lave et al. 1995兲.
Minimal straightforward guidance for the LCA practitioner for
selecting a modeling approach exists; the practitioner makes decisions based on the best available data and information. After
considering the applicability of process only, IO only, and the
range of hybrid LCA models, LCI was developed using an augmented hybrid approach. This modeling approach was chosen for
the following reasons: to decrease reliance on the limited amount
public data; to utilize available data within the context of the
existing structure of the construction industry; and to ensure that
the developed model has both depth and breadth. Since construction is a deregulated sector in the United States, environmental
process data are limited. Process data were used in this model in
conjunction with typical project records and practices when available. Additionally, the construction industry has existing financial
construction data in estimating software and scheduling tools. In
other words, available data are typically in monetary units 共cost
estimates兲 and time 共schedules兲. These monetary data can be used
in IO tools such as EIO-LCA without the need to collect additional data. Two main goals in hybrid LCA models are improving
the time and cost associated with process-based LCAs and developing an inclusive boundary. Using an augmented process-based
hybrid LCA approach achieves both of those goals.
The hybrid LCA construction model blends the most important
construction processes along with realistically assessing the availability and accuracy of data. An overall goal of the model was to
respond to the construction industry’s need to ultimately improve,
in terms of sustainability, what it can control—construction processes. Since each construction project is unique, the model allows for project specific user input, for example, project cost,
which is important for usability. The construction industry is
driven by schedule and cost, so the framework of the model centers on those two factors. Cost data are available from initial
estimates, final costs, and cost databases 共e.g., R.S. Means兲 to
name only a few. The user input and structure of the model follow
the Construction Specification Institute format along with dollar
units of demand with respect to IO information. Another important consideration in creating the model was determining data
availability and data quality. This leads to including constructionspecific process information such as AP-42 emission factors 共EFs兲
共U.S. Environmental Protection Agency 2003兲 and the use of EFs
and equipment fuel usage metrics from the Nonroad model 共U.S.
Environmental Protection Agency 2005a兲. The structure of the
model consists of three modules, namely, user input, detailed
model, and results, each described in more detail below.
Overview
The hybrid LCA construction model was created in the software
program Analytica, a visual modeling tool that can be used to
create, analyze, and communicate decision models 共Lumina Decision Systems 2006兲. Analytica has been used to support other
LCAs 共Thabrew et al. 2008; Lloyd and Ries 2009兲. The model
combines several data sources, including process, EIO-LCA, and
other data into one common LCA framework. The user inputs
required are available from typical construction process variables,
such as the dollar value of construction, the quantity of brick, and
the hours of equipment operation. Face validity with industry was
used to confirm usability and applicability of the model. The
model also calculates LCIA and displays results by impact category that will not be discussed herein.
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Table 1. Environmental Impacts Included in the Hybrid LCA Construction Model
Environmental impacts
Data sources
Dust from driving on paved roads
Dust from driving on unpaved roads
Dust generation during heavy construction operations
Welding—hazardous metals and particulates
Surface applications—application of paints, sealants, etc.
Construction services—e.g., inspection, architects, engineers, and surveyors
Equipment manufacturing
Temporary materials
Construction equipment—fuel combustion and usage
Construction equipment—extraction and distribution
Transportation of materials and workers—fuel combustion, extraction, distribution—diesel
and gasoline truck, and diesel and gasoline tractor trailer
Electricity—on-site usage, generation, distribution
Concrete water and wastewater
Model Boundaries and Major Construction Categories
The model’s scope is bounded by transportation from the manufacturer’s, supplier’s, or waste handler’s gate and includes transportation to and from the construction site, on-site construction
activities, and sectors that support construction such as construction services. The major sources of environmental impacts in construction are modeled in the categories listed in Table 1.
Transportation can include both truck transportation for materials
and equipment as well as worker transportation to and from the
site. Electricity primarily represents on-site electricity usage for
site office trailers, small equipment and tools, and lighting. Construction equipment includes not only fuel combustion but also
fuel usage, production, and distribution; construction services represent sectors such as inspectors, architects, engineers, and surveyors. Environmental effects from manufacturing permanent
materials are not included, but the full life cycle of temporary
materials such as concrete formwork is included. Permanent materials are not included because they would typically be included
in the “raw material” portion of a building LCA. Both on-site
construction waste and concrete wastewater are included, along
with emissions from welding and surface treatments such as
paints and sealants. The category “paved and unpaved roads” captures particulate emissions from vehicles traveling over a surface,
which is typically from brake wear, tire wear, and resuspended
loose road materials. Dust generation from heavy construction
operations is a particulate generation from the materials handled
rather than directly from equipment or roads.
User Input and Detailed Model
The user can input project specific characteristics in nine categories, and data can be entered as a distribution or a single value.
The nine categories are general project information, site preparation and deep foundations, concrete, masonry, steel, paints and
surface applications, transportation 共not otherwise included兲, material handling, and generator usage. For example, for general
project information, some categories include common construction information such as the dollar value of construction, project
duration, and average travel distance 共one way兲 for a concrete
truck.
The detailed model module contains the main portion of the
hybrid LCA model. In general, this module has two basic components: construction processes and data sources. The construc-
AP-42, Section 13.2.1
AP-42, Section 13.2.2
AP-42, Section 13.2.3
AP-42, Section 12.9
User provided information
EIO-LCA
EIO-LCA
EIO-LCA
Nonroad
Franklin; Idemat
Franklin
Franklin
Independent laboratory results
tion process section models the relevant construction processes
while drawing from data sources as indicated in Table 1.
Data Sources
AP-42
AP-42 EFs were used for four different elements of the model:
dust generation paved roads; dust generation unpaved roads;
heavy construction operations; and welding. AP-42, Section
13.2.1—paved roads was used to determine dust generation from
paved roads; AP-42, Section 13.2.2—unpaved roads was used to
calculate dust from unpaved roads. AP-42 EFs for paved and
unpaved roads are in units of mass of emissions per vehicle kilometer traveled.
AP-42, Section 13.2.3—heavy construction operations are
used to determine emissions from construction activities. Heavy
construction activities have a significant temporary impact on
local air quality from dust emissions, and both building and road
construction activities have high emission potential. Table
13.2.3-1 provides information on the associated sources along
with recommended EFs. An information process-specific approach, as outlined in Table 13.2.-1, was used. Specifically, information related to dozer equations in Section 11.9, western surface
coal mining 共Tables 11.9-1 and 11.9-2兲.
AP-42, Section 12.9—electric arc welding is used to determine the emissions factors related to welding. The emissions generated during welding are particulate matter and hazardous
metals, and only electric arc welding generates the pollutants in
significant quantities. Most of the particulate matter 共PM兲 generated is submicron in size, and all PM is considered to be PM-10.
The EFs were used for shielded metal arc welding, gas metal arc
welding, flux cored arc welding, and submerged arc welding:
from Table 12.19-1 共PM-10兲, EFs for welding operations and for
Table 12.19-2, hazardous air pollutant EFs for welding operations.
EIO-LCA
Inventory results from the EIO-LCA 共1997 benchmark model兲
were used for three major areas: construction equipment manufacturing; construction services; and temporary material manufacturing. The decision to use EIO-LCA as a data source was done
for two reasons—obtaining process data was not feasible and pro-
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cess data were not reliable. Since construction equipment is a
major component of construction and it is used in the construction
process, manufacturing of construction equipment is included.
Different modeling approaches were considered for this category.
For example, one option is to enter the dollar value of total
project construction equipment into the associated IO sector. This
option proved to have too many variables such as the age of the
equipment and the depreciated value and required knowledge of
specific manufacturer’s makes and models. The second option,
which was used in the model, is to enter the total value of construction in the associated IO sector and manually identify the
construction equipment sectors. These sectors are used to estimate
the impact from construction machinery manufacturing per dollar
of construction. Sectors relevant to construction equipment manufacturing selected included a range from construction machinery
manufacturing to motor and generator manufacturing. In the
model, the user inputs the dollar value of construction, which is
then multiplied by the construction equipment manufacturing results described above.
Construction services 共e.g., architects, engineers, and surveyors兲 were modeled using the same approach as construction
equipment manufacturing. The results from EIO-LCA’s Commercial and Institutional Building sector were reviewed to determine
whether the sector was deemed a construction service.
Temporary materials are included because these materials are
used directly and exclusively in the construction process. The
temporary materials for this model are related to concrete forms.
Within each of the concrete construction processes, a submodule
of concrete forms was created. Temporary materials used in formwork included in the model are wood, steel, fiberglass, and cardboard. Unlike construction equipment and services, temporary
materials cannot be selected from commercial and institutional
construction sectors because they are identical to permanent construction materials. Detailed material cost information on temporary materials was available from R.S. Means. Individual EIOLCA results were generated for four materials. Because R.S.
Means cost data were from 2006 and the EIO-LCA data were
from 1997 model 共the most recent available at the time of this
research兲 adjustments were made for deflation with one single
value.
Nonroad Output and Model Details
NONROAD2005 共U.S. Environmental Protection Agency 2005a兲
was used to model emissions from primarily nonroad equipment
combustion. While Nonroad provides several estimating and reporting capabilities, the EF information was used the most. EFs
used included grams per operating hour by source classification
codes 共SCCs兲, grams per operating hour by horsepower 共hp兲 and
SCC, grams per day by SCC; grams per day by hp and SCC,
grams per hp hour by SCC, and grams per hp hour and SCC 共U.S.
Environmental Protection Agency 2005b兲. EFs are based predominately on emission tests that were adjusted for in-use operation that differs from typical testing conditions 共U.S.
Environmental Protection Agency 2004兲. The equipment ranges
from loaders to aerial lifts.
Process LCA from Existing Databases
SimaPro, an LCA software package, allows users to conduct an
LCA with preexisting unit processes, built-in impact assessment
methods, and end-of-life options. SimaPro 5.0 is supported by
several databases with ETH-ESU 共Frischknecht and Jungbluth
2001兲 and Franklin 共Norris 2001兲 being the most extensive. Many
unit processes are available varying from “paint” to “production
of paper bags.” SimaPro, which was developed by a European
firm, contains more European-based process data. The unit processes from SimaPro that were incorporated into the hybrid LCA
model were primarily from the Franklin database, which focuses
on United States’ processes. ETH-ESU 共Frischknecht and Jungbluth 2001兲 and Idemat 共Delft University of Technology 2001兲
were also used on a minimal basis when Franklin information was
not available.
The three categories where process data are used are transportation, worker transportation, and electricity. Several Franklin database transportation processes were used with respect to
transportation, including one truck and one tractor trailer with two
fuel options. Worker transportation is modeled using an ETHESU process since the U.S. Franklin passenger car information
was not available. Electricity is modeled using the “electricity
average kilowatt hour USA” process from the Franklin database.
The model can be adjusted for specific regional electricity modeling by changing the existing unit process if required by the user
or the project. The unit process includes generation and distribution and accounts for line losses of about 8%.
Construction Processes
Modeling the construction process was a major portion of this
research. The basic structure of the model and data are based on
R.S. Means 共2006兲. Preprocessing R.S. Means information was
done in Microsoft Excel before additional model development in
Analytica. The available construction processes in the hybrid
LCA construction model are aggregated into eight main categories of site preparation, deep foundations, concrete, masonry,
steel, paints and sealants, general hauling and material handling,
and energy. Information within each construction process draws
from the references previously mentioned.
Construction has a multitude of processes, and modeling every
process was not practical. The selected construction processes
represent the major core and shell processes. While building fit
out is not included, it is possible for the user to input information
related to this phase or the building use phase in the general
hauling, material handling, paints, sealants, and energy categories.
While each construction process is unique, the structure of the
model is consistent.
Results
Result options were developed in submodules for presenting and
comparing results in both LCI and LCIA. The LCI has several
options in the LCI stage represented in seven submodules that
range from total LCI and LCIA results to local and regional inventory impacts.
In summary, the hybrid LCA construction model is a complex
model that draws from many data sources. Creating the structure
of the model and finding and integrating the appropriate data
sources were challenging from a larger scale in both framework
and structure and a smaller scale in terms of consistent units and
unit conversions. The processes created for individual construction activities are in some ways unique to each activity but in
other ways are similar. Most of the construction processes involved calculating equipment combustion and associated fuel
usage and emissions, determining transportation impacts, and estimating the amount of temporary materials. The model’s structure and readability were validated through face validity, which is
an assessment method for the relevance of the model by using
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25
15
SO2
NOx
P M10
10
5
6,000
5,000
4,000
Energy
3,000
CO2
2
Emissions (kg/m2 )
20
Energy (MJ/m ) and CO2 (kg/m2 )
7,000
\
2,000
1,000
0
Materials
Construction
Use and
Maintenance
End-of-Life
Materials
Construction
Use and Maintenance
Life Cycle Stages
End-of-Life
Life Cycle Stages
Fig. 1. Emissions by life-cycle stage—steel case study construction
results 关materials, use, and end-of-life data from Guggemos and Horvath 共2005兲兴
knowledgeable opinions from individuals. While the model is
unique to construction, the framework and approach can translate
to other applications of hybrid LCA. A LCIA calculation module
is included; however, the results are not presented in this paper.
Case Study
A steel frame structure representing a typical office building is
presented as a case study. As mentioned earlier, the material and
manufacturing phases are not included in the boundary of the
model except for temporary materials. The case study is a
17, 280-m2 core and shell office building completed in 2005 with
a steel frame. The six-story structure has a brick and curtain wall
exterior and exposed architectural and structural steel. The primary data sources for project data were construction drawings
and the construction schedule. Storm water run-off quantity and
quality were not included in this analysis since a management
plan was implemented. The storm water management plan was
approved by the County Conservation District and included elements such as inlet basin covers, silt fencing, and rock construction entrances.
Case study results from this research 共SO2, NOx, PM10, energy,
and CO2兲 from the construction phase were compared with other
life-cycle stages 共material production, use and maintenance, and
end of life兲 to determine the significance of the construction phase
to the other phases. Data from the life-cycle stages 共material production, use and maintenance, and end of life兲 were obtained
from Guggemos and Horvath 共2005兲; data from this case study
were used because they are also a steel framed structure. The data
from Guggemos and Horvath 共2005兲 were normalized on a square
meter basis. For PM10, construction is relatively high, illustrating
the importance of construction for local and regional impacts 共see
Fig. 1兲. PM10 is primarily due to vehicles and equipment traveling
on paved and unpaved roads and earth moving activities. SO2
emissions from construction 共2%兲 are lower than the other phases
except end of life. For NOx, construction and end of life 共8%兲
have the lowest emissions of all the phases with the highest at
70% from the use phase. In terms of CO2, construction is the third
highest 共Fig. 2兲. Energy, materials, and construction are almost
the same in terms of percentage of energy use.
Sensitivity Analyses
Sensitivity analyses were performed on key components of the
model to better understand elements of uncertainty and key vari-
Fig. 2. Energy and CO2 by life-cycle stage—steel case study construction results 关materials, use, and end-of-life data from Guggemos
and Horvath 共2005兲兴
ables that can greatly impact the results. Varying levels of analyses were performed ranging from broader factors to specific
variables in equations. In total 13 scenarios were investigated and
grouped into several categories 共see Table 2兲.
The service sectors to include in the model from EIO-LCA
results are somewhat subjective and therefore, a sensitivity analysis was performed. The model takes a fairly broad view of service
sectors, which results in service sectors representing about
$4,330,000 or 33% of the $13,000,000 construction cost. A more
narrow interpretation of service sectors such as architects and
engineers only results in service sectors representing 22% of the
construction cost. Global warming potential 共GWP兲 results indicate that service sector selection range has relatively minimal
impact 共see Fig. 3兲. The major impacts related to on-site construction were captured in the traditional service sectors. Detailed processes positively impacted the results; however, it would be very
difficult to determine the quantitative level of the impact.
Conclusions
The foci of this research were construction, hybrid LCA modeling, and context. First, in terms of commercial core and shell
construction in the United States, the research determined the LCI
and impact assessment of the construction processes of a typical
steel-framed commercial building in the U.S. LCI results included
292 substances but focused on PM emissions, GWP, SOx, NOx,
CO, Pb, nonmethane volatile organic compounds, energy usage,
and solid and liquid wastes. The model results were compared
Fig. 3. Global warming potential comparison from an example sensitivity analysis of broad and narrow service sectors from inputoutput life-cycle assessment results
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Table 2. Sensitivity Analysis Scenarios
1
2
3
4
5
6
7
Ratio between diesel and gasoline equipment
Ratio between diesel and gasoline transportation fleets
Transportation distance for concrete supplier
Transportation distances with respect to vehicle weight
Number of construction workers and distance traveled
Vehicle weights traveling on paved and unpaved roads
Service sector selection
with building life cycle results from published work. The comparison indicated that construction, while not as significant as the
use phase, is as important as the other life-cycle stages and that
PM emissions are significant in the construction phase.
Second, with regard to hybrid LCA modeling, the augmented
process-based LCA proved to be effective in modeling construction. A framework that allowed for efficiently combining process
and IO modeling, especially for the construction sectors, is critical in construction LCA modeling. In the steel case study, services had the highest level of methane emissions, and they were a
significant contributor to CO2 emissions. Third, hybrid LCA modeling requires both breadth and depth. For example, the model not
only includes construction processes from site preparation to
painting but also includes detailed modeling of construction
equipment combustion. Modeling a diverse mix of construction
equipment improves the usability and applicability of the construction LCA and improves the accuracy of the results.
The research found that it is critical to include service sectors
in LCAs and EIO-LCA is an effective source for service sector
data. This finding pertains not only to construction but can also
extend to LCAs in other domains as well; for example, this approach is currently being used to model construction products,
such as insulating concrete forms and pultruded composites 共Rajagopalan et al. 2009兲. With respect to on-site construction and
GWP, emissions from electricity are insignificant since electricity
accounts for less than 6% of overall CO2. While this research
focused on commercial construction in the United States, the
framework can be extended to other construction types and countries, including developing countries. The framework allows for
considerable flexibility with minimal effort to make changes to
data sources. Examples of changes to the model in developing
countries may include changes to combustion emissions for construction equipment, fuel usage, and equipment types. Developing
countries may also employ different construction practices and
levels of equipment use. The model may also be used to compare
not only the entire project but also different construction activities, such as comparing the environmental impacts of augercast
piles versus driven steel piles. The overall body of knowledge of
construction LCAs needs to be further developed and expanded,
and this research contributed to its development. The model will
be posted online in the future. Additional research and especially
case studies are needed so that deeper and more in-depth comparisons can be made to further refine the results.
Acknowledgments
Financial support for this research was provided by National Science Foundation Grant No. CMS-0327878. Any opinions, findings, and conclusions or recommendations expressed in this
material are those of the writer共s兲 and do not necessarily reflect
the views of the National Science Foundation. The writers would
also like to thank Dr. Aurora L. Sharrard for helpful discussions
and the reviewers.
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