1. EXECUTIVE SUMMARY
Due to tremendous increase in
population globally over the years, the need for the sustainable housing development
is gaining significance. The residential units are the major source of energy
consumption. Due to advancement in technologies in building construction
techniques over the years there is potential to save the energy loss. Life
cycle assessment is well accomplished technique that has been employed to
calculate the primary energy uses and associated environmental impacts during different
stages of the building such as: embodied stage, maintenance stage and
demolition stage. In this study the life cycle assessment of two residential
units; home of today and home of tomorrow is performed. Home of today is
basically equipped with the conventional construction materials being used in
residential construction industry whereas home of tomorrow is equipped the
environmental friendly construction materials. These two different alternatives
of residential units in Kelowna (BC, Canada) with a 50-year lifespan have been
evaluated and comparison is carried out for the primary energy, embodied
energy, demolition energy consumption and associated environmental impacts.
Estimation of operational energy and LCA are performed using HOT 2000 software
and Athena Impact estimator software respectively. The study results revealed
that over the life span of the buildings, the relationship between the energy
use and the environmental impacts are identical. Home of tomorrow is found to
be the best alternative in terms of embodied energy use and embodied
environmental impacts. Sensitivity analysis has also been carried out to study
the influence of building service lifespan over 50, 75, and 100 years on the
relative significance of embodied energy and total life cycle energy.
The human demands in growing urban environment,
including residential housing, water and food supply, health care facilities,
efficient transport, and disposal of domestic waste are dependent on the
construction industry. All these facilities, significantly utilizes the
resources and energy, and leads to adverse environmental impacts, such as generation
of greenhouse gases leading to climatic changes, generation of wastewater,
emissions and solid waste 1. Since, residential buildings holds the major
share of entire land use serving the largest number of consumers are the major
contributors to the environmental impacts. In the United States, building industry
accounts for 39% of the total primary energy use, 38% of carbon equivalent
emissions, and 40% of all raw material use annually; the statistics in Canada
are almost the same 2. Such consequences has increased the need of
sustainable housing development 3. The environmental aspects are increasingly
more significant in sustainability. Therefore, environmental assessment of
building is a right approach to attain the goal of sustainability. In general,
Life-Cycle Assessment (LCA) technique is employed in building industry to
quantify and evaluate the environmental aspects during its whole life time that
is from cradle to grave including the extraction of raw materials,
construction, utilization, end of life, and beyond building life 4. Many LCA
studies have been conducted in building sector, various studies mainly focused
on residential buildings. For example, 5 presented the method to calculate
the energy use during the life cycle of a building and in the same year studied
the life cycle of three single unit dwellings in Sweden. Reference 4 studied
the LCA for three bedroom semidetached house in Scotland. This study is focused
on five construction materials and their embodied energy, and associated
Greenhouse gas (GHG) emissions. Reference 6 compared the high and low-density
residential buildings in Toronto (ON, Canada) for their energy use and
associated GHG emissions. Two functional units are selected for this study:
living area (m2) and number of people in a house (per capita basis) and it is
demonstrated that the choice of functional unit is vastly relevant for full
understanding of urban density effects. The study found that, low-density
suburban development consumes 2.0-2.5 times more energy and GHG intensive than
High-density urban development on per capita basis. Reference 7 studied the
two-storey single family residential building located in Vancouver, Canada.
This study focused on construction materials, and manufacturing and operation
phases of a building. This study also shows that operational phase contributes
high environmental impacts. Reference 8 proposed the ‘energy-based’ LCA
framework and compared the single-family and multi-family residential buildings
in four Canadian provinces. Nevertheless, this study was not intended to select
the better sustainable building; instead this study offered a sustainability
assessment tool by providing quantitative and transparent results for informed
decision-making. In conclusion, existing literature on the LCA of building
focuses primarily on the energy use and greenhouse gas emissions of small to
mid-size houses. However, neither the full life cycle (cradle to grave) nor
full range of impact categories that generally included in LCA is considered.
The purpose of this study is to contribute towards a better understanding of
the full LCA impacts of residential buildings in Canada by focusing on home of
today and home of tomorrow. The main objective of this study is to evaluate and
compare the primary energy use and the potential environmental impacts (EI)
associated with the alternatives for residential buildings by using the
concepts of LCA. This study considered whole life cycle phases of buildings
with 50 years lifespan. In order to attain the main objective, the following
sub objectives have to be fulfilled:
? Analyzing the operational energy of
the building by performing energy simulation
Identifying the best housing type consuming very less energy and contributing
to the least environmental
? Perform the sensitivity analysis for
four types of houses over 50, 75, and 100 year lifespan
The following sections represents the
present and comparison of the life cycle energy use and EI of each type of the
house. It is anticipated that the results of this study would be beneficial for
a wide range of stakeholders, including planners, engineers, developers, and policy
The methodology is represented in this
section for the present study. The approach to carry out the analysis for the
energy consumption and environmental impacts is described below
Cycle Analysis (LCA)
To obtain the specified results the
Life Cycle assessment methodology is selected in case of this study. As there
are number of methods available to calculate the environmental impacts but
these methods have certain shortcomings. But LCA is well defined approach and
is restricted strictly to the use of ISO 140-43 standards9–12. The
modelling for the LCA is done in Athena Impact Estimator (Athena IE) for
buildings 13. According to ISO 14040, there are four LCA analytical stages:
1. Goal and scope definition for LCA
2. Determine the LCI for materials and
their corresponding environmental impacts
3. Generating impact assessment data
using the LCI reports
4. Results interpretation
The first stage of the LCA is to define
the scope and boundaries of the system. The goal of the study is to evaluate
the life cycle energy use and EI of typical types of houses in Canada and to
scrutinize whether the obtained results are significantly skewed by the type of
house. These results are then used to evaluate the overall energy use and
impacts from the Canadian housing sector with the aim of identifying the best
alternative. The functional unit is considered as 1m2 of floor area of a house
over its lifetime. A 50 year lifespan was assumed for this study, which is
commonly used by researchers in LCA study of building. Also, this allows for a
significant time period for repair, and replacement of building materials. The brief
description of each type of house is summarized in section B. The framework for
system boundaries and outputs of this LCA study are shown in Fig. 1.
Fig. 1: LCA system boundaries and
As can be seen, the system boundaries
can be divided into three distinct phases, i.e. the pre-occupancy, the
occupancy, and the post occupancy. The outputs comprises of the total primary
energy use and the EI for all phases. The stage two of LCA study is life cycle
inventory (LCI), starts with making a process tree or a flow-chart classifying the
events in a building’s life-cycle which are to be considered in the LCA, plus
their interrelations. This procedure is followed by data collection, where
quantitative and qualitative data for all inflows and outflows, such as raw
materials, energy, ancillary products, land use and emissions are gathered. The
next step in LCI is to calculate the amount of energy used and emissions of the
studied system in relation to its functional unit 10, 14. In this study,
the Athena IE software is used to assess the material and energy inputs and outputs.
The stage three of LCA study is life cycle impact assessment (LCIA), which
calculates the potential EI and estimates the energy used in the studied system
or process. The detailed LCIA results are presented in results and discussion
section. Finally, the last stage of LCA study is interpretation, which is an
iterative process present during all phases of the study. The findings of the
LCI and LCIA are combined here in order to achieve the recommendations and
conclusions for the study.
In this study, two types of residential
buildings in Kelowna (BC, Canada) are used as a case study to demonstrate the
mechanism of this research method. This home is built to minimum code
home of today is built to minimum code requirements.
Equipment and construction is of a standard nature, in order
to give a baseline comparison to the Home of Tomorrow:
• HVAC: 92 % efficient 60,000 btu natural gas furnace c/w single stage psc
blower c/w 14.5 seer 3 ton AC.
• Nu Air non dedicated HRV system.
• Fireplace: heat & glo DV3732SBI direct vent gas fireplace.
• Plumbing: standard fixtures. 60 gal elect HWT.
• Windows: vinyl double glazed windows c/w 180 low E.
• Insulation: R-22 batt walls, R-40 blown in ceilings, 2 lb Sprayed joist ends.
• Lighting: Incandecent
• Appliances: Standard
The Home of Tomorrow is built to higher energy
• HVAC: 5 series – ground source heat pump c/w ECM
variable speed blower
• Zoned ducting (1 @basement/1 @ main)
• Solar panels: CSUN Quasar 260 – connected to a Fortis net meter
• Life Breath RNC155 dedicated HRV system
• GE Geospring Pro heat pump water heater
• Fireplace: Marquis 46? Skyline 2 ZRB46NE gas direct vent
• Plumbing: water saving toilets and faucets
• Windows: vinyl triple glazed windows c/w double 366 low E
• 12 inch Insulated Concrete Form (ICF) foundation walls at entire basement
• QuikTherm 2? styrofoam wall system, c/w R14 batt insulation on the main floor
• R-20 batted and R-50 blown in ceilings (total R-70), 2 lb Urethane Spray at
• Lighting – LED
• Appliances: induction range, double ovens (clients can use the smaller oven
the majority of the time and save power), 5 door fridge (allowing the client to
access smaller cavities resulting in less temperature fluctuations due to cold
air loss), heat pump dryer (brand new technology resulting in significant gains
in efficiency. These dryers are also condensing units and do not require
• Energy Star rated hood fan with LED lighting and ultra-quiet blower
• Energy efficient dishwasher
• Energy management and climate control system by Honeywell
B. Athena Impact Estimator for
Athena Sustainable Materials Institute,
a non-profit organization based in Ontario, Canada developed the ATHENA® Impact
Estimator for Buildings. The Institute’s mission is to promote sustainability
in the built environment through the use of LCA in North America. Notably, it
is the only software tool presently available in North American context. The
Athena IE was developed as a support tool to aid in the decision making process
at the conceptual design stage. The software provides a cradle-to-grave LCA for
a building and individual assembles. This software generates the bill of
materials based on the given inputs, this can be compared with expected
outcome, and in case of any discrepancies the material quantities can be
adjusted using ‘additional materials’ input feature. The Athena IE takes into
account any or all of the following building characteristics and life-cycle
factors to measure the impact in each of the metrics: Material manufacturing,
including resource extraction and recycled content, transportation, On-site
construction, regional variation in energy use, transportation and other
factors, type of building and lifespan, maintenance and renovation effects, end
of life management.
Calculating Embodied Energy Use and
the environmental damage caused by houses over its life cycle is a challenging
task. Embodied energy is the energy used during the construction stage of a
building, it includes the energy incurred at the time of erection/construction
of materials, as well as the renovation of building components 16. According
to 17, LCI involves the collection of data and modeling to estimate the total
amounts of emissions, waste, energy used, and materials used throughout the
life cycle of a building 18. Although specific techniques are available to
manually conduct LCI, various computer software tools develop din the recent
past have superseded these techniques. Calculating the energy use and
environmental impacts at each stage of the house including raw materials
extraction, manufacturing of building materials, construction, maintenance, end-of-life
management, transportation during all of these stages is computationally intense.
The HOT 2000 software is used for calculating the embodied energy. The method
evaluates different categories of environmental impacts, including,
acidification, eutrophication, smog potential, fossil fuel consumption, global warming,
human health particulate, non-renewable energy, and ozone depletion. Each house
in this study is separately modeled as precisely as possible using the gathered
inputs. Athena IE generated the detailed bill of quantities for each house.
Unfortunately, the embodied effects associated with the electrical, HVAC, and
plumbing services in a building cannot be calculated using Athena IE. Hence,
these embodied effects have not been considered in this study. The Athena IE
can evaluate only the embodied energy, and currently there is no option for
evaluating the operational energy of a building. Yet, it consists of a
calculator that transforms the estimated operational energy into primary energy
over a building’s life cycle. However, this estimation of operational energy
use must be calculated using additional building energy simulation software
Table 2: Home of Today
Table 3: Home of Tomorrow
D. Calculating Operational Energy Use and Environmental Impacts
During occupancy in a building,
operational energy is required for space heating, space cooling, lighting,
domestic hot water, and equipment; however, it varies significantly based on
the level of comfort, climatic conditions and the operating schedules 16.
Currently, various computer applications are available to calculate the
operational energy of a building. For this study, Athena Building Impact
Estimator software is selected for the purpose. In general, energy can be
classified in to two major types, primary and secondary energy. As mentioned
earlier, in this study, the Athena IE for buildings evaluates embodied energy in
terms of primary energy and the HOT 2000 evaluates the secondary energy. The
estimated secondary energy (i.e. embodied or site energy) and energy mix (i.e. electricity,
natural gas, geothermal, etc.) have been used as the inputs to Athena IE to
calculate the resulting total primary energy use and total environmental
impacts. 2. Later, the obtained annual energy use values are entered in
Athena IE to get the total operating energy and environmental impacts.
Table 4 : LCA Measure by Assembly Group
Table 4: LCA Measure by Assembly Groups
(A to C)
Table 5 : Comparison of Total Primary
Energy by Life Cycle Stage
Table 6: Green Globes LCA Measures
Comparison Report Cradle to Grave
E. Calculating Total Life Cycle Energy Use and Environmental
two major outputs of this study are the total life cycle energy consumption and
the total life cycle environmental impacts. The total life cycle energy
consumption in million joules (MJ) of each house is the sum of total embodied
energy and the total operational energy over the lifespan of 50 years. In this
study, total embodied energy, total operational energy, and total life cycle
energy are presented in terms of primary energy consumption. The total life
cycle EI is also estimated similar to total energy use. The total life cycle EI
of each house is the sum of total embodied EI and the total operational EI over
50 years of lifespan.
4. RESULTS AND DISCUSSION
In this section, the results of a
comprehensive LCA study of two types of residential buildings in BC, Canada are
presented. The presentation of results is divided into the
Following categories: total embodied
energy and environmental impacts, total operating energy and embodied impacts.
a. Total Embodied Energy Use and Environmental Impacts: A breakdown of total embodied energy
for two types of buildings for a service life of 50 years. The results are
divided into the relevant building life stages:
product, construction process, use or
maintenance, end of life, and beyond building life. The total embodied energy
of buildings of home of tomorrow is less than home of today. In terms of the
total embodied EI, the relationship between the EI and the embodied energy are
much the same. The foundation and walls for all the building types are responsible
for maximum embodied EI.
1 Environmental impacts of the UK
residential sector: Life cycle assessment of houses Rosa M. Cuéllar-Franca,
2 Life cycle environmental
performance of material specification: a BIM-enhanced comparative assessment Saheed O.
Gallanagh & Kabir O.
3 Environmental Life Cycle Analysis
of Office Buildings in Canada F. A. Amin
Ganjidoost and S. A. Sabah Alkass
M. Asif, T. Muneer, and R. Kelley, “Life cycle assessment: A case study Of a
dwelling home in Scotland,” Build. Environ.
5 K. Adalberth, “Energy use during
the life cycle of buildings: a method,” Build. Environ. vol. 32, no. 4, pp.
317–320, Jul. 1997.
6 Energy use during the life cycle of
single-unit dwellings: Examples
links open overlay panel K .Adalberth
J. Basbagill, F. Flager, M. Lepech, and M. Fischer, “Application of lifecycle assessment
to early stage building design for reduced embodied
environmental impacts,” Build. Environ.
vol. 60, pp. 81–92, Feb. 2013. 8 J. Norman, J. Norman, H. L. MacLean, H. L.
MacLean, C. a. Kennedy, and C. a. Kennedy, “Comparing High and Low Residential
Life-Cycle Analysis of Energy Use and
Greenhouse Gas Emissions,” J. Urban Plan. Dev., vol. 132, no. 1, p. 10, 2006.
9 W. Zhang, S. Tan, Y. Lei, and S.
Wang, “Life cycle assessment of a single-family residential building in Canada:
A case study,” Build. Simul., vol. 7, no. 4, pp. 429–438, 2014.
10 B. Reza, R. Sadiq, and K. Hewage,
“Emergy-based life cycle assessment (Em-LCA) of multi-unit and single-family
residential buildings in Canada,” Int. J. Sustain. Built Environ. vol. 3, no.
2, pp. 207–224, Oct. 2014.
11 I. O. for S. ISO 14040,
“Environmental management: life cycle assessment. Principles and framework,”
12 I. O. for S. ISO 14041, “ISO 14041
Environmental management — Life cycle assessment — Goal and scope definition
and inventory analysis,” 1998.
13 I. O. for S. ISO 14042, “ISO 14042
Environmental management – Life cycle assessment – Life cycle impact
14 I. O. for S. ISO 14043, “ISO 14043
Environmental management — Life cycle assessment — Life cycle interpretation,”
15 A. I. E. AIE, “Athena Impact
Estimator for Buildings and the Athena EcoCalculator for Assemblies,” http://www.athenasmi.org/,
16 H. Baumann and A.-M. Tillman, The
Hitch Hiker’s Guide to LCA. 2004.
17 O. S. Asfour and E. S. Alshawaf,
“Effect of housing density on energy efficiency of buildings located in hot
climates,” Energy Build., vol. 91, pp. 131–138, Mar. 2015.
18 I. O. for S. ISO 14044, “ISC
14044: Environmental Management — Life Cycle Assessment— Requirements and
19 Sun, M.; Kaebernick, H.; Kara, S.
Simplified life cycle assessment for the early design stages of industrial
products. CIRP Ann-Manuf. Techn. 2003, 52, 25-28.
20 X. Li, F. Yang, Y. Zhu, and Y. GAO,
“An assessment framework for analyzing the embodied carbon impacts of
residential buildings in China,” Energy Build., vol. 85, pp. 400–409, Dec.
21 Heijings (2002) Heijungs, R . and
Suh, S ., “The Computational Structure of Life Cycle Assessment,” Kluwer