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Emissions of Materials Benchmark Assessment for Residential Construction (EMBARC)

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Abstract and Figures

The report analyses the embodied carbon 503 as-built low-rise homes in the Greater Toronto and Hamilton Area. Based on a A1-A3 analysis using the BEAM tool, the results ranged from a high of 90.7 tonnes of CO2e to a low of 9.5, with a mean of 42.9 tonnes. The material carbon intensity for heated floor area ranged from a high of 561 kg CO2e/m2 to a low of 116, with a mean of 191. Extrapolated to all annual construction of this type in the region, embodied carbon from the materials considered in the report is approximately 840,000 t CO2e. Concrete, insulation and cladding were the three material categories with the highest impact, and suggestions for achieving reductions are explored. The use of carbon storing materials was explored by applying different materials to several of the homes in the study, demonstrating that reductions in net emissions between 51-177% are achievable, with some results demonstrating net carbon storage.
Content may be subject to copyright.
Emissions of Materials
Benchmark Assessment
for Residential Construction
Table of Contents
Acknowledgments ..................................................................... 1
Executive Summary ....................................................................2
Putting Material Carbon
Emissions into Context ................................................................4
Previous Studies of Material Carbon Emissions .............................................. 5
Emissions of Materials Benchmark
Assessment for Residential Construction (EMBARC) ....................................... 6
Methodology .............................................................................7
2.1 New Home Starts ................................................................................. 8
2.2 Sample House Plans ............................................................................ 8
2.3 Material Carbon
Emissions (MCE) Calculations ..................................................................... 9
2.3.1 BEAM Methodology .......................................................................... 9
2.3.2 Carbon Storage .............................................................................. 10
2.3.3 Cradle to Gate Focus on Structural,
Enclosure & Interior Surface Materials ......................................................... 12
2.3.4 BEAM Limitations ............................................................................ 14
Results & Discussion ................................................................. 15
3.1 Material Carbon Emissions (MCE)
and Material Carbon Intensity (MCI) ........................................................... 15
3.1.1 Housing Typology and MCI ............................................................... 20
3.1.2 Combining Material and
Operational Emissions: Carbon Use Intensity ............................................... 21
3.2 Material Analysis ................................................................................24
4. Effects of Material
Substitutions on MCI ............................................................................... 32
Conclusions .............................................................................37
Recommendations for Policy Makers ...........................................40
Industry Recommendations .......................................................45
Endnotes ................................................................................46
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 1
Acknowledgments
Passive Buildings Canada is Canada’s first national
non-profit organization supporting the passive house
community to build a more sustainable Canada and
planet. We welcome a diversity of approaches and
voices to connect, share knowledge, and promote
passive house projects.
Builders for Climate Action is creating tools,
research and resources to support practitioners
and policy makers in making zero carbon buildings.
Chris Magwood, Erik Bowden and Mélanie Trottier
prepared this report on behalf of BfCA.
This report has been made possible by a grant from
The Atmospheric Fund, a regional climate agency
that invests in low-carbon solutions for the Greater
Toronto and Hamilton Area and helps scale them
up for broad implementation. TAF are experienced
leaders and collaborate with stakeholders in the
private, public and non-profit sectors who have ideas
and opportunities for reducing carbon emissions. TAF
advances the most promising concepts by investing,
providing grants, influencing policies and running
programs. TAF is particularly interested in ideas
that offer benefits beyond carbon reduction such as
improving people’s health, creating new green jobs,
boosting urban resilience, and contributing to a fair
society.
The team would like to thank Gaby Kalapos at the
Clean Air Partnership for her insights, support
and assistance in working with the municipalities
of the GTHA.
The team would also like to express their sincere
appreciation to Eve Treadaway for her work in
organizing the data for this study and Javaria Ahmed
for her assistance in entering building plans into
BEAM.
Thanks to reviewers: Ryan Zizzo, Founder & CEO,
Mantle Developments; Kelly Alvarez Doran, MASS
Design Group and Associate Professor, University
of Toronto; Lisa King, Senior Policy Planner, City of
Toronto; and Roya Khaleeli, Director, Sustainability
Innovation - Minto Communities Canada.
Thanks as well to everyone who provided feedback
and comments, who are too numerous to name.
Arista Homes
Country Homes
Chatsworth Fine Homes
Geometra Designs
Minto Communities
OPUS Homes
Sustainable TO.
Westpark Homes
Cities and Regional Municipalities of:
Durham
Hamilton
Toronto
York
Municipalities of:
Burlington
Halton Hills
Milton
Oakville
Brampton
Caledon
Mississauga
This report has been made possible in part thanks to data and advice from:
Suggested citation: Magwood, C., Bowden, E., Trottier, M. Emissions of Materials Benchmark Assessment for
Residential Construction Report (2022). Passive Buildings Canada and Builders for Climate Action.
Report layout and design by FrolicDesign.ca
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 2
Executive Summary
Rich Data Set
EMBARC generated a rich data set, representing
503 as-built homes of three key typologies:
single detached, semi-detached and townhouses.
Together, these housing types represent an
average of 16,400 new homes built annually in
the region.
Building Emissions Accounting for Materials
The BEAM (Building Emissions Accounting for
Materials) estimator tool was used to assess GHG
emissions and carbon storage for building materials
that make up the structure, enclosure and main
finishes, based on results from Environmental
Product Declarations. Emissions from raw
material harvesting, transportation to factory and
manufacturing (A1-A3) were considered. Mechanical,
electrical and plumbing materials, millwork, stairs,
doors and surface finishes were not calculated.
503 homes = 20,122 tonnes of emissions
Material carbon emissions (MCE) across the study’s
sample of 503 as-built housing units totalled an
estimated 20,122 tons, with an average of 40 t CO2e
per unit. The lowest emitting home was responsible
for 9.5 t CO2e and the highest 827.1 t CO2e.
16,400 homes = 840,000 tonnes of emissions
Extrapolating the study’s average values to all new
low-rise homes built each year in the GTHA, the total
annual MCE may be around 840,000 t CO2e annually.
This is equivalent to the emissions from more than
183,000 automobiles.
As the MCE measured in this study may represent as
little as 50 percent of the total MCE for these building
typologies, due to the exclusion of MEP equipment,
appliances, finishes and millwork, a possible impact
of 1.75 Mt (megatonnes) of MCE is likely arising from
new home construction.
Material Carbon Intensity
Material carbon intensity (MCI) was calculated by
dividing total emissions by floor area, to enable
comparisons between units of different sizes.
MCI was calculated using various definitions of floor
area, with the weighted average results:
Gross oor area — 154 kg CO2e/m2
Heated oor area — 189 kg CO2e/m2
Habitable oor area — 225 kg CO2e/m2
Depending on the floor area definition, each of
the three housing typologies could be the best or
the worst, indicating the importance of accurately
defining the parameters for MCI.
Based on heated floor area, the lowest MCI result
was 116 kg CO2e/m2 and the highest was 561 kg
CO2e/m2. The 189 kg CO2e/m2 average MCI for
heated floor area was higher than the 150 kg CO2e/
m2 average from previous studies, due largely
to bigger garages and more use of high emission
cladding (brick) and insulation (XPS foam).
High Emission Materials
73 percent of all material carbon emissions in the
study come rom just three material categories:
concrete (33 percent for foundation walls, slabs and
footings), insulation (26.1 percent for foundations,
walls and roofs) and exterior cladding (13.4 percent).
Efforts to reduce MCEs should be concentrated on
these material categories.
We Can Make a Dierence
Material substitutions were explored for a home
with heated floor area MCI of 116 kg CO2e/
m2. Using the “best available materials” (widely
available, affordable and code-compliant), this
could be reduced to 56.5 kg CO2e/m2. If all new
homes in the GTHA used the “best available
materials” this would result in approximately
573,000 t CO2e fewer emissions annually.
Using the “best possible materials” (feasible but
unconventional), this could be further reduced to
-54.6 kg CO2e/m2, indicating that homes could
become sites of net carbon storage, rather than
net emissions.
Using the “best possible materials” would result in
the reduction of roughly 1,065,000 t CO2e. In this
hypothetical scenario, new Part 9 homes built in
the GTHA would pass beyond net zero carbon to
store around 225,000 tonnes of carbon from the
atmosphere during a single construction year.
The New Direction
The researchers recommend that policy makers
and the home building sector begin to regularly
measure MCE and MCI for new homes, and
implement voluntary thresholds in line with the
average results from this study. Regulation of MCE
may enable region-wide emission reductions of
250,000 to 1,000,000 t CO2e annually.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 3
Using the BEST
available materials we
can reduce emissions
by 50%
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 4
Putting Material Carbon
Emissions into Context
Canada, and the entire world, is faced with a rapidly
declining “carbon budget” within which we must
function to stave off the worst effects of climate
change. The United Nations has declared the climate
emergency “code red for humanity.”1 The Pan-
Canadian Framework on Clean Growth and Climate
Change (PCF, 2016) identified the building sector as
one of the major contributors to GHG (greenhouse
gas) emissions in Canada.2 To this end, improvements
in energy efficiency have been integrated into the
National Building Code of Canada and the Ontario
Building Code as well as municipal incentives and
voluntary green building standards in order to reduce
emissions from new homes.
The very short amount of time available to meet
Canada’s emission reduction targets of 40-45 percent
below 2005 levels by 20303 requires us to consider all
of the emission impacts from the housing sector and
focus effort on those sources of emissions that have the
greatest immediate impact on our remaining carbon
budget. In recent years, increased attention has been
drawn to the emissions arising from building materials,
oen referred to as “embodied carbon,” (this
report uses the more specific term “material carbon
emissions”(MCE) to describe the cradle-to-gate phases
of life cycle assessment 4). Early research5 6, in this
field indicated that over the next two crucial decades
these emissions are likely to substantially outweigh the
operational emissions attributed to newly
constructed homes.
50
45
40
35
30
25
20
15
10
5
2020 2025 2030 2035 2040 2045 2050
Remaining Global Emissions Budget
PHASE OUT
340 GtCO2
(1.5°C, 67% Chance)
500 GtCO2
(1.5°C, 50% Chance)
660 GtCO2
(1.5°C, less than 50% Chance)
67%
50%
33%
Emissions from buildings
need to be reduced by
50-67% to meet IPCC
1.5°C targets
Figure 1: Emission reduction pathways to meet IPCC 1.5C targets Adapted from Architecture 2030.
Figure 2:
Results of MCE studies
Canada-wide
NRCAN Study
Canadian average of three
archetypes and 190 models
British Columbia
Nelson & Castlegar Study
34 as-built homes
Total Net
EMISSIONS
72
kgC02e/m2
Lowest Carbon
Result
Total Net
EMISSIONS
150
kgC02e/m2
Average Carbon
Result
Total Net
EMISSIONS
309
kgC02e/m2
Highest Carbon
Result
Total Net
STORAGE
-50
kgC02e/m2
Best Possible
Materials
Total Net
EMISSIONS
2
kgC02e/m2
Best Available
Materials
Total Net
EMISSIONS
150
kgC02e/m2
Moderate Carbon
Materials
Total Net
EMISSIONS
513
kgC02e/m2
High Carbon
Materials
Canada-wide
NRCAN Study
Canadian average of three
archetypes and 190 models
British Columbia
Nelson & Castlegar Study
34 as-built homes
Total Net
EMISSIONS
72
kgC02e/m2
Lowest Carbon
Result
Total Net
EMISSIONS
150
kgC02e/m2
Average Carbon
Result
Total Net
EMISSIONS
309
kgC02e/m2
Highest Carbon
Result
Total Net
STORAGE
-50
kgC02e/m2
Best Possible
Materials
Total Net
EMISSIONS
2
kgC02e/m2
Best Available
Materials
Total Net
EMISSIONS
150
kgC02e/m2
Moderate Carbon
Materials
Total Net
EMISSIONS
513
kgC02e/m2
High Carbon
Materials
Previous Studies of Material Carbon Emissions
In 2021, Natural Resources Canada (NRCan) released
the report “Achieving Real Net Zero Emission Homes7
establishing that material carbon emissions (MCE)
for new homes will outweigh operational carbon
emissions (OCE) for electrified homes using relatively
clean electrical grids such as that in the Greater
Toronto and Hamilton Area (GTHA) for almost 120
years. At the highest levels of energy efficiency
proposed by codes, this imbalance extends to 166
years of OCE to equal MCE. According to these
results, MCE would represent a large majority of
a new home’s total emissions over the next few
decades. Le unchecked, MCE is likely to undercut
the gains made in reducing operational emissions
over the past decade.
Using archetype home designs for a bungalow,
two-storey and row house the NRCan report used
four material palettes to reflect different MCE
outcomes: high, mid-range, best available and
best possible materials.
The study found that the average measured MCE for
Tier 38 homes across five Canadian cities could vary
widely based on these material selections, from a
high of 513 kilograms of emissions per square meter
of heated floor area (kg CO2e/m2) to a low of -50 kg
CO2e/m2. The model using the most conventional
mix of materials showed 150 kg CO2e/m2 and the
model using materials with the lowest emission profile
that are widely available and code compliant was
2 kg CO2e/m2.
In 2021, Builders for Climate Action worked with
the cities of Nelson and Castlegar, BC, to examine
the MCE of 34 as-built homes in the region9. The
measured results included a high of 309 kg CO2e/m2
and a low of 72. The average across the 34 samples
was 150 kg CO2e/m2. A local home that was not
included in the study but measured using the same
methodology matched the NRCan “best available
materials” result of 2 kg CO2e/m2.
Both studies revealed that total MCE from new
homes represents a significant, mostly overlooked
and unregulated, pool of GHGs. Nationally, an
average of 150 kg CO2e/m2 for all new housing
construction would represent total GHG emissions of
8.5 million tonnes annually based on average annual
construction10.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 5
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 6
Emissions of Materials Benchmark
Assessment for Residential Construction (EMBARC)
The EMBARC study examines MCE in the GTHA using
a large sample of as-built new Part 9 homes and
the same methodology as the NRCan and Nelson/
Castlegar studies. The intent of the study is to provide
an understanding of the total impact of MCE from new
Part 9 homes on the region’s emissions and provide
decision makers – including policymakers, developers,
home designers and builders, as well as homeowners
– with insights on how this MCE can most effectively
be reduced in future construction of the GTHAs
housing stock.
EMBARC generated a rich data set,
representing 503 as-built homes of three
key typologies: single detached, semi-
detached and townhouses. Together,
these housing types represent an average
of 16,400 new homes built annually in
the region, based on data from 2017-
2020 collected from municipalities by the
research team.
A detailed analysis of each set of home plans in the
free soware program BEAM (Building Emissions
Accounting for Materials) enabled the study team
to generate total MCE for each home, as well as a
material-by-material breakdown.
This report offers many insights into MCE from Part
9 homes and ways in which it can be dramatically
reduced. These emissions are considered “Scope
3” – generated by manufacturers across North
America (and indeed around the world) – and are
therefore not typically addressed by municipalities.
However, decisions made by municipal policymakers
and the local building sector can have significant
and immediate impacts on these emissions.
Addressing MCE at the regional level is an example
of acting locally to make important impacts globally,
and we look forward to sharing and discussing
the recommendations in this report widely with
stakeholders in the region to encourage action
on MCEs.
On a positive note, this study does not only point out
a problem, it also provides clear recommendations for
how to minimize the problem. Unusual for a report on
climate change, this study suggests that new homes
could potentially become sites of negative emissions,11
with atmospheric carbon stored in building materials
outweighing all associated manufacturing emissions
and providing a net reduction in atmospheric carbon.
While it is beyond the scope of this report to consider
the future supply chains necessary for a carbon-storing
homebuilding sector, we want to be sure to point
toward the economic potential of using the vast array
of regionally available carbon-storing raw materials
in new regional manufacturing of building materials
and components. As there is much talk of post-
pandemic “building back better” we can think of no
better way to do so than by lowering CO2 levels in the
atmosphere while making energy efficient and healthy
buildings out of materials that boost all sectors of our
regional economy.
?
TERMINOLOGY
MCE Material Carbon Emissions
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 7
59
SAMPLE
HOUSE
PLANS
Extraction of
Raw Materials
Transport of
Raw Material
Processing into
Building Products
Standardized Environmental
Product Declarations
(EPDs)
BEAM results for 59 sample
house plans from 8 developers
BEAM estimator applies
EPD factors to individual
home plans
EPD
BEAM
CALCULATIONS
A1 A2 A3
+ +
59
house plans
represent
503
as-built homes
TOTAL
Material Carbon
Emissions
Extrapolation of results to
annual construction of new
homes in GTHA
Methodology
The researchers chose to use the same methodology as earlier Canadian
studies of MCE, following the steps illustrated in Figure 3.
Figure 3. EMBARC study
methodology diagram
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 8
2.1 New Home Starts
Each municipality in the GTHA was approached to
ascertain the number of new Part 9 homes constructed
between 2017-2020, composed of three typologies:
single detached, semi-detached and townhouses. The
annual average total is 16,428 units. The results for
each typology are shown in Table 1.
Table 1. Average annual new dwelling unit completions
by building type and municipal region (GTHA, 2017-2020
annual average).
Average annual new Part 9
dwelling unit completions in GTHA
Municipal
Region Single
Detached Semi-
detached Town-
house Total
Durham 1,452 84 989 2525
Halton 1,188 169 1,036 2393
Hamilton 580 54 881 1515
Peel 2,165 419 1,137 3721
Toronto 1,122 92 570 1784
York 2,564 205 1,721 4490
GTHA 9,071 1,023 6,334 16,428
% of
total units 55% 6% 39%
2.2 Sample House Plans
The researchers contacted developers and builders
across the GTHA with a request for Part 9 residential
plans that met the criteria of the study. Eight
developers/builders in the region supplied plans for
the study, with the majority sharing plans for numerous
homes they have constructed in the GTHA between
2017 and 2020. Most of the shared plans represent
more than one constructed building. The researchers
were informed of the number of times each sample plan
was actually constructed during the period of the study.
The researchers analyzed 59 different plan sets which
represent 503 homes built in the GTHA region. Table 2
shows a breakdown of the plan sets by typology
and built examples.
Table 2. Plan sets and number of plan sets built
Building
Archetype Plan count per
archetype Quantity of
plans built
Single Detached 19 116
Semi-detached 5 38
Townhouse 35 349
Total 59 503
Single Detached 32% 23%
Semi-detached 8% 8%
Townhouse 59% 69%
The sample size is 3.1 percent of the total number of
new single detached, semi-detached and townhouses
typically completed annually in the GTHA. This data
set of homes is the largest sample in the world of MCE-
analyzed residential buildings employing a consistent
methodology.
The study sample set acquired underrepresented single
detached homes by 23 percent and overrepresented
townhouses by 21 percent. Where applicable, the
researchers adjusted for this in the calculations, as well
as for the discrepancy between the sample plan floor
areas and the average floor areas for the GTHA for each
of the three archetypes. Floor areas for the GTHA were
extracted from Milton building permits from 2017-
2020, as no other municipality included floor area data
in their building reporting. While Natural Resources
Canada has national floor area statistics up to 2018,12
the researchers decided this was not regionally specific
enough, thus Milton’s floor area values were chosen to
represent all of the GTHA.13
59
SAMPLE
HOUSE
PLANS
59
house plans
represent
503
as-built homes
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 9
2.3 Material Carbon
Emissions (MCE) Calculations
Each set of plans used in the study was entered into a
beta version of a spreadsheet application called BEAM
(Building Emission Accounting for Materials). BEAM
was developed by Builders for Climate Action and
shares an overlapping database and methodology
with the Material Carbon Emissions Estimator (MCE2)
tool from Natural Resources Canada. BEAM and
MCE2 were developed specifically for Part 9
residential construction and include all materials/
products used in residential applications for which
there was sufficient, reliable data available at the time
of the study.
TERMINOLOGY
MCE Material Carbon Emissions
GWP Global Warming Potential
BEAM Building Emission Accounting for
Materials
EPD Environmental Product Declarations
BEAM estimator applies
EPD factors to individual
home plans
BEA M
CALCULATIONS
Standardized Environmental
Product Declarations
(EPDs)
EPD
2.3.1 BEAM Methodology
BEAM is based on a methodology common for
embodied carbon calculations. The Global Warming
Potential (GWP) factors for materials are gathered
from Environmental Product Declarations (EPDs),
which are third-party certified reports prepared
according to ISO 14025 in addition to either EN
15804 or ISO 21930: 2017. 14 In some cases, an EPD
must also conform to ISO 1407115. Where no EPDs
exist for a product, BEAM uses an average GWP
result from all applicable peer-reviewed life cycle
assessments (LCAs) of the product.
The GWP factors in BEAM are a sum of life
cycle stages A1 (raw material acquisition), A2
(transportation of raw materials to manufacturing
facility) and A3 (manufacturing emissions). This is
oen referred to as a “cradle to gate” analysis and
makes up the “material carbon emissions” that are
the focus of this study.16
GWP factors are quantities of GHG emissions
arising from specific life cycle stages, expressed in
kilograms of carbon dioxide equivalent (kg CO2e)
per given “functional unit” of a material or product
(e.g. 1 m3, 1 kg, 1 m2 , depending on the product).
BEAM calculations begin with entering the relevant
building dimensions from the plan set, which are
then used as the basis for calculating material
quantity estimations. Fields are provided in BEAM to
further specify key dimensions and factors used to
complete quantity estimations, such as R-value for
insulation, framing spacing, and concrete wall and
floor thickness. With all material quantity information
entered, BEAM provides the GWP for every material
in a given assembly. BEAM presents the user with
an average GWP factor for all products in a given
material category, or allows for selecting the result
for a particular product within the category. For the
EMBARC study, average results were selected unless
there was a clear product name specified in the plans
and a corresponding EPD for that product in BEAM.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 10
2.3.2 Carbon Storage
BEAM accounts for carbon storage in products that
contain biogenic materials sourced from agricultural
or forestry residues and recycling streams. In such
cases, the mass of biogenic material per functional
unit is determined according to the product EPD
or LCA and the mass of carbon within that biogenic
material is calculated based on chemical composition
analysis results from the Phyllis database17. The net
GWP emissions for the product is the result of the
A1-A3 carbon emissions minus the biogenic carbon
storage. The net emissions for some biogenic materials
therefore have a negative value when carbon storage
is greater than carbon emissions. These net negative
emissions materials are oen termed “carbon-storing”
materials.
No carbon storage attributed
to virgin forest products
While there is a standard methodology in ISO 21930
for determining biogenic carbon storage credits for
products, there remain important and unresolved
concerns with current accounting methods related
to virgin forest products like lumber. Some of these
concerns include uncertainty about the amount of
carbon released from soils during logging operations;
the amount of carbon returning to the atmosphere
from roots, slash and mill waste; the amount of carbon
storage capacity lost when a growing tree is harvested;
and the lag time for newly planted trees to begin
absorbing significant amounts of atmospheric carbon
dioxide. These factors and others are being researched
and deliberated by experts from academia, the
forestry industry, the building industry, environmental
advocacy organizations, and LCA professions. Because
these critical issues were unresolved at the time of this
study, the BEAM version used for the study excluded
biogenic carbon storage for products made of raw
logged timbers (including framing lumber, plywood,
OSB and wood trusses and I-beams).
The Positive Impact of Durable
Carbon Storage: Ton Year Accounting
While there is consensus that storing carbon for a
period of time has a mitigating impact on climate
change, there has been considerable debate
about how to account for the value of temporary
carbon storage. The Moura Costa method18 of ton-
year accounting establishes the value of carbon
dioxide stored in durable products such as building
materials. As shown in Figure 4, a one metric ton
of carbon dioxide emissions causes 46 ton-years of
radiative forcing damage to the climate over a 100-
year timeframe (the area in grey). Drawing one ton of
carbon dioxide
out of the atmosphere and storing it for a period of
46 years mitigates the climate damage from one ton
of CO2 emissions (the area in green).
The materials attributed carbon storage by BEAM
have anticipated lifespans of at least 46 years
and can thus be said to have at least the positive
climate impact of their full carbon content. Many
such materials will last longer than 46 years in a
building, and may therefore increase the storage
value; materials removed from the building before
reaching 46 years could have their carbon storage
value discounted accordingly (see Table 3).
Durable Biogenic
CARBON STORAGE
in Buildings Equivalent Areas
46 Ton-years
Climate Damage Avoided
100
Yea rs
46
Yea rs
0
Yea rs
of biogenic carbon
stored for 46 years
OFFSETS
100 years
of damage
1 ton
of biogenic carbon
released into
the atmosphere
1 ton
4
6
T
o
n
-
y
e
a
r
s
o
f
C
l
i
m
a
t
e
D
a
m
a
g
e
(
w
a
r
m
i
n
g
)
1 ton
of CO2
emissions
1 ton
of CO2
removal
Table 3. Examples of carbon offset value of biogenic
carbon for various time horizons.
Ton Year Equivalency Factors for
Biogenic Carbon
Biogenic
Carbon Stored Duration of
Storage Equivalent Oset
of Present-day
Emissions
100 tons 1 year x 2.17% 2.17 tons
100 tons 20 years x 2.17% 43.4 tons
100 tons 46 years x 2.17% 100 tons
100 tons 80 years x 2.17% 174 tons
The factors in Table 3 assume that 100 percent of the carbon
contained in the material will return to the atmosphere when
removed from the building. Any material reuse, recycling or
carbon capture (or a percentage of carbon materials put in
landfill that do not decompose) would alter these scenarios
accordingly, as any carbon that remains out of the atmosphere
would continue to have a positive impact on the climate.
For a world with a rapidly dwindling carbon budget and
ample opportunities for biogenic carbon storage in the built
environment, this methodology offers a great deal of potential
to encourage this type of climate mitigation.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 11
Figure 4. Graphical representation of
the Moura Costa method to establish the
carbon offset equivalence of biogenic
carbon storage in building materials.19
Adapted from Srubar et al., A
Methodology for Build- ing-Based
Embodied Carbon Offsetting (2021)
12
2.3.3 Cradle to Gate Focus on Structural,
Enclosure & Interior Surface Materials
This study and the BEAM tool focus on lifecycle stages A1 to A3 emissions (defined in 2.3.1) because they
represent the majority of the life cycle GHG emissions from building products, typically accounting for
70-80 percent of life cycle emissions from buildings20. For the first 30 years of a building’s lifespan (that
is, before substantial repairs or replacements of materials occur), A1-A3 emissions account for over 90
percent of material emissions. Given the timelines we are facing for dramatically reducing emissions, this
methodology prioritizies the time value of addressing A1-A3 emissions.
Using the building plans, each material for each assembly in the building is selected, and the kg CO2e
results are calculated both for the assembly and for the whole building. Once all materials have been
selected, BEAM provides a total for Material Carbon Emissions (MCE) for the building in both kilograms
and tonnes of CO2e, as well as the Material Carbon Intensity (MCI) which is the MCE divided by the floor
area of the building in kilograms of CO2e per square meter (kg CO2e/m2).
This study, and the BEAM tool, focus on the main structural, enclosure and interior surface elements of a
new Part 9 home. Figure 5 shows the materials that are included in this study.
Footings and slabs
Foundation walls
Structural elements
(posts and beams)
Exterior walls
Party walls (where
applicable)
Exterior cladding
Windows
Interior walls
Floors
Ceilings
Roof
Figure 5. Materials
included in the study.
These elements of the building were
selected for four key reasons:
They represent the majority of the overall material mass
There is good quality EPD and LCA data available for all
common options in these categories
They typically have lifespans of at least 25-30 years and
oen last as long as the building
There are meaningful, immediately available design
options and/or material substitutions available in each of
these areas that allow a home builder to substantially alter
the emissions prole of the building
By addressing the bulk of a new home’s emissions and focusing on
those areas in which significant reductions can be achieved, we
believe this approach maximizes the utility of the results.
Each set of plans was entered into BEAM by a member of the
Builders for Climate Action team, familiar with the soware. A
review of each entry was conducted by a different team member to
ensure accuracy.
The BEAM calculations for each individual set of plans were then
compiled into a spreadsheet that enabled the researchers to
examine the results by home, typology, location, size, material
category and material type.
1
2
3
4
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 13
14
2.3.4 BEAM Limitations
The results derived from BEAM should be considered estimates of emissions, and not definitive quantities.
Results from BEAM are similar in nature to those obtained from energy modeling soware, from which
comparative results from different materials and strategies can be accurately derived, but from which actual
energy use may not be accurately predicted.
It is important to note that BEAM will underestimate the total emissions arising from materials for a new home
because a number of significant material categories are not currently considered within BEAM, including:
It is possible that with all of
the above elements added
into MCE calculations, the
results in this study may
represent as little as 50
percent of the total material
emissions impact for new
home construction. Any
extrapolation of the total
impact of new home MCE
across the study region
should be done with
awareness of these
omissions.
Mechanical, electrical and plumbing (MEP)
materials. These are excluded due to a lack of
available EPD data and lack of meaningful substitutions
in each category. Material GHG emissions from MEP
could range from 40-75 kg CO2e/m2, which could add
an additional 26-49 percent to the average gross floor
area MCI for homes in this study.21
Paints and surface finishes. These are excluded
because the lifespan of these materials is typically
shorter than the minimum 25 year lifespan required
for inclusion in BEAM. They do, however, contribute
significantly to the MEC of a new house. A typical single
detached house in this study has approximately 750
m2 of wall and ceiling area that would be painted, and
an average interior paint (all coats) has emissions of 3.5
kg CO2e/m2, resulting in an additional 2.6 tonnes of
emissions or 6 percent of the average emissions for a
home of this size.22 Finishes for trim, doors
and millwork would add to this total.
Fixtures and appliances. These are excluded
due to lack of available data and lack of meaningful
substitutions. Many of the key components of fixtures
and appliances (steel, stainless steel, copper, porcelain)
are known to have substantial MCE but few EPDs or LCA
studies of specific products exist.
Millwork, stairs, cabinetry and trim. These
are excluded due to lack of available data and lack of
meaningful substitutions.
Decks, driveways, earth moving,
excavations, and all site works. These are
excluded due to the variability and complexity of
adding these to the study.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 15
Results & Discussion
The results from the EMBARC study provide insights at the level
of the entire housing sector in the region, individual houses,
material categories and specific materials.
3.1 Material Carbon Emissions (MCE)
and Material Carbon Intensity (MCI)
Each set of plans entered into BEAM was assessed for its net material carbon emissions
(MCE), the total of all material emissions minus any biogenic carbon storage. Table 4
summarizes the overall measured MCE results.
Table 4. Net MCE results for all measured materials
Net Material Carbon Emissions for 503 GTHA Sample Buildings
Statistic Type MCE
[kg CO2e] MCE
[t CO2e]
Best / Lowest Home Result 9,517 9.5
Worst / Highest Home Result 827,117 827.1
Mean (Average) 56,163 56.2
Standard Deviation 104,188 104.2
Weighted Avg by Qty Built 40,006 40.0
Median 39,350 39.3
Total of individual sample homes (59) 3,313,557 3,314
Total of sample
homes built (503) 20,121,858 20,122
Across the study’s sample of 503 as-built housing units, an estimated 20,122 t CO2e
was emitted, giving a weighted average of 40 t CO2e per unit. Extrapolating the study’s
average values to the 16,428 Part 9 homes typically built annually in the GTHA, and
adjusting for the average archetypal floor areas for each region, the total annual MCE
from new Part 9 homes may be roughly around 840,000 t CO2e annually.
This is the equivalent of the annual emissions from
more than 183,000 automobiles.23
TERMINOLOGY
kg CO2e Kilograms of carbon dioxide equivalent
t CO2eTonnes of carbon dioxide equivalent
MCI by Floor Areas
800
700
600
500
400
300
200
100
0
Total Floor Area
454
561
726
560
373
329
325
244
223
187
153
263
224
185
152
116
236
173
149
130
104
Heated Area Habitable Area
Unit Area Type (MCI Denominator)
Material Carbon Intensity
[kg CO
2
e / m
2
]
800
700
600
500
400
300
200
100
0
Material Carbon Intensity
[kg CO
2
e / m
2
]
159
191
235
MCE by House Typology
MCI by House Type
100
90
80
70
60
50
40
30
20
10
0
Semi-detached
42.8
90.7
53.9
90.7
60
39.3
28.9
9.5
9.5
18.5
31.6
35.4
56.1
61.5
66.6
77. 7
35.1
41.1
39.4
37. 2
Single Detached Townhouse
House Typology
Net Material Carbon Emissions
[tonnes CO
2
e]
All Typologies
Semi-detached Single Detached Townhouse
Building Typology
All Typologies
39.2
69
29.9
42.9
By Total Floor Area By Heated Area By Gross Floor Area By Habitable Area
Mean
Max
Min
80th Percentile
Median
20th Percentile
Mean
Max
Min
80th Percentile
Median
20th Percentile
LEGEND:
LEGEND:
Mean
Max
Min
80th Percentile
Median
20th Percentile
LEGEND:
In comparison to other emissions sources in the region, this figure is slightly higher than
GHGs from residential waste (724,337 t CO2e) and well above agriculture (422,186 t CO2e).
Material carbon emissions assessed for these three archetypes of homes in the GTHA
represents approximately 1.5 percent of total carbon emissions in the region in 202024.
As discussed in Section 2.3, the MCE measured in this study may represent as little as
50 percent of the total MCE for these building typologies, due to the exclusion of MEP
equipment, appliances, finishes and millwork, suggesting a possible impact of 1.75 Mt
(megatonnes) of embodied carbon emissions from new GTHA Part 9 residential building
construction annually.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 16
Figure 6. Total emissions are lowest for townhouses and highest for single detached,
largely due to differences in size. For all typologies, the median for the 503 homes was
39.3 tonnes of CO2e.
=
=
CITY SCALE
Annual Emissions
40 t CO
2
e
A single house avg.
840,000 t
CO
2
e
GTHA extrapolation
for materials included in the study
1,750,000 t
CO
2
e
GTHA extrapolation including
materials not calculated in this study
3,314 t CO2e
59 house plans
183,000
Annual Automobile
Emissions
59
SAMPLE
HOUSE
PLANS
20,122 t CO2e
503 as built homes
TOTAL
Material Carbon
Emissions
380,000
Annual Automobile
Emissions
Missing building types for
a complete emissions inventory
This study examines only new residential
buildings that meet the requirements of Part
9 of the Ontario Building Code, representing
only 44 percent of residential units constructed
annually in the GTHA. Part 3 (large) apartment
and condominium units are built in greater
quantities and are not captured in this study.
A more complete assessment of overall
residential-sector MCE in the GTHA region
would also need to consider the impacts of
renovation materials for existing buildings.
A complete assessment of all building MCE
emissions of the GTHA would need to include
all non-residential buildings as well. A study
from The City of Toronto, The University of
Toronto and Mantle Developments25 assesses
MCE of some types of Part 3 (large) buildings
in the region. The average A1-A3 emissions for
38 buildings in the study was 345 kg CO2e/
m2, significantly higher than for the low-rise
buildings studied in EMBARC.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 17
Size matters
In the study, the smallest floor area belonged to a townhouse unit
of just 48 m2 (517 2) and the highest to a single family home of
1,475 m2 (15,880 2), a 31-fold increase in floor area. As might be
expected, such variation in home size has a direct influence on total
MCE.
Table 5 shows results by housing typology (isolating an exceptionally
large single family home outlier from the rest) and demonstrates the
influence of home size on MCE. The floor area reported in this table
is heated (also known as ‘conditioned’) floor area, which excludes
garage areas.
Table 5. Home size and average MCE.
Home size and average MCE and MCI
Housing typology Number of sample
plan sets Average MCE,
kg CO2eAverage heated
oor area, m2Average MCI,
kg Co2
Single detached 18 69,010 411 172
Semi-detached 5 39,209 241 173
Townhouse unit 35 29,951 166 193
Large single
family home 1 827,117 1,475 561
The MCE averages tend to vary proportionally with the size of the
units. Excluding the large single family dwelling, the average size of
a semi-detached home and a townhouse were 41 and 60 percent
smaller than the average single detached, respectively. Their MCE
averages were 43 and 57 percent lower than the average single
family home, demonstrating a correlation between size and MCE.
MCE is a useful metric for assessing the total GHG impact of any
particular house and of housing in the region. In order to recognize
the clear relationship between home size and emissions Material
Carbon Intensity (MCI) can be used. MCI is the result of total building
MCE divided by floor area (in square meters). MCI allows a relative
comparison of large homes to small homes and can be used to
project how material changes might affect homes regardless of
their size.
In this study, MCI was calculated using total building floor area,
heated floor area (excludes garage) and habitable floor area
(excludes garages and unfinished basements). Table 5 summarizes
the MCI results.
TERMINOLOGY
MCE Material Carbon Emissions
MCI Material Carbon Intensity
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 18
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 19
Total floor area MCI for the weighted average of the 503 homes is 159 kg CO2e/m2, which is 17 percent lower
than MCI for heated floor area and 32 percent lower than habitable floor area (Figure 7). This points to the
importance of identifying the metric used to calculate MCI when comparing results. The need for industry and
regulators to agree on appropriate metrics for MCI is addressed in Section 6.3.
MCI by Floor Areas
800
700
600
500
400
300
200
100
0
Total Floor Area
454
561
726
560
373
329
325
244
223
187
153
263
224
185
152
116
236
173
149
130
104
Heated Area Habitable Area
Unit Area Type (MCI Denominator)
Material Carbon Intensity
[kg CO
2
e / m
2
]
800
700
600
500
400
300
200
100
0
Material Carbon Intensity
[kg CO
2
e / m
2
]
159
191
235
MCE by House Typology
MCI by House Type
100
90
80
70
60
50
40
30
20
10
0
Semi-detached
42.8
90.7
53.9
90.7
60
39.3
28.9
9.5
9.5
18.5
31.6
35.4
56.1
61.5
66.6
77.7
35.1
41.1
39.4
37. 2
Single Detached Townhouse
House Typology
Net Material Carbon Emissions
[tonnes CO
2
e]
All Typologies
Semi-detached Single Detached Townhouse
Building Typology
All Typologies
39.2
69
29.9
42.9
By Total Floor Area By Heated Area By Gross Floor Area By Habitable Area
Mean
Max
Min
80th Percentile
Median
20th Percentile
Mean
Max
Min
80th Percentile
Median
20th Percentile
LEGEND:
LEGEND:
Mean
Max
Min
80th Percentile
Median
20th Percentile
LEGEND:
0%
0%
BEST
116
kg CO2e/m2
MCI
AVERAGE
191
kg CO2e/m2
MCI
WORST
561
kg CO2e/m2
MCI
Best, average and worst
MCI for Heated Floor Area
Figure 7. Material carbon intensity varies depending on the
defination of floor area being used.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 20
3.1.1 Housing Typology and MCI
Examining the MCI results by housing typology and by different definitions of floor area
highlight how important the selection of metrics for MCI can be. Depending on the metric
chosen, different typologies can be seen as best or worst.
Examined by total floor area, the difference in results for each typology are minimal, with
semi-detached the lowest MCI at 144 kg CO2e/m2 and single detached and townhouses
5 and 8 percent higher.
Table 6. MCI can be considered by floor area designation and/or house typology. Defining
these parameters will be important for policy makers.
Examined by heated floor area the differences get
larger. The weighted average for semi-detached
homes in this study had the lowest MCI, at 156 kg
CO2e/m2, with single detached homes 7 percent
higher and townhouses 22 percent higher.
Using a definition of gross floor area employed by
some municipalities in the GTHA (which counts garage
area but ignores basement area), the townhouse
becomes the best result at 185 kg CO2e/m2, with
single detached 11 percent higher and semi-detached
14 percent higher.
Using only habitable floor area as the basis for MCI
semi-detached homes have the lowest result, 5 and 7
percent lower than townhouses and single detached,
respectively.
Clearly, the choice of metrics for measuring MCI can
have an important impact on the results for different
types of homes. As discussed in Section 6.3, policy
makers must weigh the impacts of the metrics they
select carefully to ensure they support other municipal
priorities such as density.
The study of material carbon emissions is relatively
new. The intent of this study is to help inform potential
policy action to incentivize or regulate these emissions
in the home building sector. Effective policy will
require appropriate metrics to ensure that policies
do not create perverse incentives or negatively
impact other policy priorities. As the results of this
study demonstrate, changing the unit upon which
emissions intensity is measured can dramatically alter
the results. For example, calculating MCI by total
floor area compared to heated or habitable floor
area can change the MCI result by 19 and 32 percent,
respectively.
Priorities such as increasing residential density,
reducing uninhabited space or emission reductions
through renewable energy systems could be
incorporated into a new metric. The researchers
explored Material Carbon Intensity by Function, or
MCIF (see Sidebar XX) as an example of a metric that
can combine desired outcomes.
Material Carbon Intensity (MCI)
[kgCO2e/m2] (weighted average)
Area Type Single
Detached Semi-
detached Townhouse All Types
Total oor area 152 144 156 154
Heated oor area 167 156 199 189
Municipally dened gross oor area 209 216 185 193
Habitable oor area 229 213 224 225
3.1.2 Combining Material and
Operational Emissions: Carbon Use Intensity
The EMBARC study did not include the operational
carbon emissions (OCE) of the homes in the study.
However, consideration of both MCE and OCE is
critical to understanding a more complete scenario of
emissions arising from new homes.
Carbon Use Intensity (CUI) is a metric that adds a
home’s operational carbon emissions (OCE) to its
MCE to demonstrate the total impacts of both these
significant factors. Since OCE accumulates annually,
the CUI metric is usually associated with a particular
time period. CUI can be expressed according to a
number of years (ie. CUI30 would be the total of MCE
and OCE over a 30 year period) or according to a
fixed time window (ie. CUI2030 would be the total
of MCE and OCE between the date of construction
and the year 2030). Either version of the CUI metric
would allow regulators to compare the combined
operational and material emissions associated with a
new home to their broader climate mitigation targets.
The NRCan report Achieving Real Net Zero Emission
Homes discusses the importance of considering CUI:
“The effort to shi to a CUI metric could, despite the
challenges, put the sector on the proper footing to
meet the country’s 2050 climate goals in a way that is
more holistic and offers more flexibility to the unique
conditions that exist in every region where homes
are built.26 The “flexibility” refers to the options le
to builders to weigh the impacts of energy efficiency
measures, fuel choices and material selection to best
meet the needs of their homeowners while adhering
to the climate goals of the country, province and/or
municipality.
MANUFACTURING
EXTRACTION TRANSPORTATION
+ +
Material Carbon
Emissions
(MCE)
+= CUI
ENERGY
USE INTENSITY
+
ENERGY
SOURCE EMISSIONS
Operational Carbon
Emissions
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 21
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 22
Figure 8 shows the CUI30 results from the NRCan
study for a model two-storey home in Toronto and
demonstrates how the variables of energy efficiency,
fuel choice and MCE can impact overall emissions
over a 30 year period. By working with a CUI metric,
the builder could determine the best path to meeting
a CUI target.
Consideration of MCE as an important factor in
overall emissions from the homebuilding sector is
very recent. The selection of a metric for calculating
and reporting MCE will have an important impact on
how MCE is addressed and potentially regulated and
should be an important part of ongoing discussions.
28.4 t MCE 14.2 t OCE
CUI for Toronto 2-storey home scenarios
Moderate
Emissions Materials
Code Compliant,
Electric Heat Pump
BUILDING
SPECIFICATIONS MCE
OCE
(FOR 30 YEARS)
CARBON USE
INTENSITY
42.6 t
CUI20
31.2 t MCE 8.8 t OCE
Moderate
Emissions Materials
Net Zero Ready,
Electric Heat Pump
40 t
CUI
20
4.2 t MCE 8.8 t OCE
Best Available
Materials
Net Zero Ready,
Electric Heat Pump
13 t
CUI
20
30.5 t MCE 69.6 t OCE
Moderate
Emissions Materials
Net Zero Ready,
Gas Heat
100.1 t
CUI
20
Figure 8. Carbon Use Intensity for the same home design is impacted by both MCE and OCE.
Energy efficiency, fuel type and material selections all have an impact on CUI.
Exploring new
metrics for MCE:
Four performance criteria were chosen by
Erik Bowden, one of the study’s authors, to
be addressed by a new MCI metric, which
aims to have positive carbon and housing
availability impacts for regions that adopt it.
These include increasing housing occupancy
capacity, using the number of bedrooms as a
proxy for occupancy, decreasing uninhabited
space, decreasing gross building size relative
to occupancy, and decreasing the building’s
overall MCE.
Using these factors, Bowden proposes
a derived metric called Material Carbon
Intensity by Function, or MCIF, with the units of
t CO2e/bedroom.
The lower the value obtained, the better
the building is at achieving the performance
criteria, overall.
A ratio of gross floor area to habitable floor
area was applied, rather than only dividing
by floor area as is typical, to encourage the
optimal use of constructed space. As this ratio
decreases from one, the MCIF increases. For
example, if half of the floor area is unfinished
basement and garage space, the MCIF is
doubled. In cases where all floor area is
habitable (i.e. a 1:1 ratio), there is no impact on
the metric.
To address housing needs in combination
with material carbon, it is proposed that the
number of bedrooms per housing unit be
included in the MCIF metric as a proxy to
occupancy capacity. All other factors being
equal, a home with more bedrooms will have
a proportionally lower MCIF value.
Unifying these four factors into MCIF is
just one suggested method among many
emerging ways of evaluating a home’s
emissions intensity. One downside of MCIF
could be that with simplification, resolution
of the contributing factors is lost. Though
slightly more complex, it may prove to be
better to use multiple separate metrics in
coordination in order to maintain resolution,
such as total MCE, MCI/bedroom and MCE/
m2 of habitable floor space, each with their
own benchmarks and bounds. Ultimately,
as long as these separate metrics are used
concurrently to focus evaluation on the
desired goals, deleterious effects caused by
any one metric should be constrained by
the others.
C = net MCE in t CO2e,
B = quantity of bedrooms in the unit
A = gross area in m2, and Ah = habitable area in m2.
MCIF = C A
B Ah
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 23
3.2 Material Analysis
All new homes are amalgamations of many different
materials. The BEAM models for each home in this
study provide insights about material use that can
be helpful at different levels: comparison of broad
material categories, comparison within material
categories, and materials with high per-use emissions
or carbon storage. Each level can help focus
regulatory, design and procurement attention where
impacts can be greatest.
Material Categories
Material categories capture the impacts of materials
that may show up in more than one assembly in a
home, such as concrete (in slabs, basement walls,
garage floors, and footings.) and insulation (in floors,
walls and roofs). Figure 9 shows the total emissions
attributed to each of the main materials categories in
all 503 sample homes.
Concrete, insulation, and cladding are the three
most emission-intensive categories of Part 9 home
building material, together representing 72 percent
of the measured MCE. Serious emission reductions in
these three categories would be the most impactful
interventions, and each is explored in more
detail below.
STRUCTURAL
POSTS AND BEAMS
1,022,555 kg CO2e
5.1%
CONCRETE
6,647,924 kg CO2e
33%
Includes footings,
foundation walls & floor slabs
INSULATION
5,242,864 kg CO2e
26.1%
Includes walls, roofs,
floors and foundations
CLADDING
2,575,309 kg CO2e
12.8%
INTERIOR
SURFACES
2,166,831 kg CO2e
10.8%
Includes flooring,
walls & ceilings
FRAMING
633,257 kg CO2e
3.1%
WINDOWS
1,385,851 kg CO2e
6.9%
ROOFING
447,537 kg CO2e
2.2%
Figure 9. Total emissions from 503
homes by material category.
72%
of total MCE
from just three
material categories!
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 24
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 25
CONCRETE
32.9%
INSULATION
26.3%
CLADDING
13.3%INTERIOR
SURFACES
10.1%FRAMING
6.8%WINDOWS
5.1%
ROOFING
2.2%
3.2.1 Concrete
Concrete plays an important role in new homes,
as it is the dominant material choice for footings,
foundation walls and floor slabs. Every home in
the study used concrete for these elements. The
pervasiveness of the material along with its relatively
high MCE means that the concrete components
of GTHA homes had the largest impact on overall
emissions, representing 33 percent of total emissions
from new homes. Figure 10 shows the contribution of
concrete, rebar and reinforcing mesh to this total.
The impact of concrete emissions is sizable as
calculated, but may be understated (or, less likely,
overstated) due to a lack of product-specific data
about concrete mixes in the building plans and from
GTHA regional plants.27
For determining the carbon emissions of concrete,
the BEAM tool uses an Environmental Product
Declaration prepared by the Canadian Ready Mix
Concrete Association28 which presents industry-wide
average data. For concrete in the 0-25 MPa (~3,000
psi) compressive strength category (typical for use in
Part 9 homes), this EPD presents 19 different possible
mix designs, each with different GWPs that range
from a high of 327 to a low of 214 kg CO2e/m3. This
EPD declares an “Industry Average Benchmark” of
305 kg CO2e/m3 and this is the figure selected in
BEAM for all concrete calculations in this study.
CONCRETE
5,967,177 kg CO2e
89.8%
WIRE MESH
86,354 kg CO2e
1.3%REBAR
588,830 kg CO2e
8.9%
Figure 10. Concrete emissions by
component material.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 26
The EC3 (Embodied Carbon in Construction Calculator) tool29 is the largest repository of
construction material EPDs in North America, and while it contains 109 product-specific EPDs for
0-25 MPa (28 day compressive strength) concrete from Canadian manufacturers, none of these
originate from Ontario. More broadly, the lowest GWP for Canadian concrete in EC3 is 93 and the
highest is 828 kg CO2e/m3. EC3 calculated an average of 390 kg CO2e/m3 for Canadian concrete
calculated using uncertainty factors arising from the quality of data used in generating EPDs. Table
7 shows the impact on overall concrete emissions in this study by applying different GWP factors
for 0-25 MPa concrete.
Table 7. Comparison of possible GWP factors for 25 MPa concrete in Canada
*Total GWP for concrete only, does not include rebar or mesh
Concrete Mix GWP
Factor
kg CO2e/m3
Emissions from 503
samples,
kg CO2ePercentage
change from
benchmark
CRMCA - 0-25 MPa,
Canadian Benchmark Avg. 305 4,269,344*
Butler Concrete N254 124 1,738,469 -59%
LaFarge ECOPact RMXUG35A3A8M 170 2,383,385 -44%
CRMCA Mix #19 - 0-25 MPa, 35-50% Slag, GUL 214 3,000,260 -30%
CRMCA Mix #18 - 0-25 MPa, 35-50% Slag, GU 234 3,280,660 -23%
CRMCA Mix #10 - 0-25 MPa, 30-40% Fly Ash, GU 250 3,50,478 -18%
CRMCA Mix #12 - 0-25 MPa, 25-34% Slag, GU 268 3,757,337 -12%
CRMCA Mix #6 - 0-25 MPa, 15-29% Fly Ash, GU 283 3,967,635 -7%
CRMCA Mix #1 - 0-25 MPa, 0-14% FA/SL, GU 327 4,584,512 +7%
EC3 Avg. for 107 Canadian 25 MPa concrete EPDs 390 5,467,766 +28%
EC3 Conservative estimate for Canadian 25 MPa 507 7,108,096 +66%
LaFarge RMXK925A21F 610 8,552,147 +100%
Concrete mix design can have a large impact on GWP factors. The use of supplementary
cementitious materials (SCMs), including fly ash and blast furnace slag, account for 25
percent of the difference between results in the CRMCA EPD (it is important to note that
availability of fly ash and slag quantities will diminish as the emissions-intensive industries
that produce these byproducts are scaled down over the next decades). Use of Type 1L/GUL
(Portland-Limestone) Cement offers a 5-15 percent reduction in GWP, and in combination
with high percentages of SCMs can bring overall emission reductions of up to 35 percent, as
seen with Mix #19.
If the EC3 average of 390 kg CO2e/m3 is applied to all 0-25 MPa concrete in this study,
overall emissions would increase from the 4,269 t CO2e assumed in the study to 5,468 t
CO2e, a 28 percent increase.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 27
At worst, 0-25 MPa concrete with a high GWP factor
of 610 kg CO2e/m3 (as would be the case with five
Canadian EPDs found in the EC3 database) would
raise concrete emissions in this study to 8,552 t CO2e,
a 100 percent increase. If GTHA builders were able to
access the best-possible 0-25 MPa Canadian concrete
mix, emissions would be reduced by 2,531 t, a 59
percent reduction.
The wide range of results arising from different
concrete GWP factors points to the importance of
obtaining reliable, manufacturer-specific EPD data for
concrete for GTHA homes. Without such data, taking
quantifiable action on the largest source of emissions
from new home construction will be difficult.
The BEAM tool enables users to input “User Defined
Options” and this would enable information from
any valid concrete EPD from a local supplier to be
calculated in a model. The use of product specific
EPDs in the concrete category is an essential step in
properly assessing the emissions and reductions in
this critical category.
While mix design offers opportunities for emissions
reductions, it is possible for new homes to be
designed to use less concrete by minimizing below-
grade construction and/or substituting materials such
as treated wood foundations. Homes built above-
grade using pier or pin foundations can eliminate
concrete use altogether. It is beyond the scope of
this study to directly analyze the minimization or
elimination of concrete, but while concrete is the
largest contributor to MCEs these options may be
worth further exploration.
Changes in concrete mixture formulation has
implications beyond emissions. Mixes with high
proportions of SCMs can take longer to cure and
therefore impact construction schedules. While it is
beyond the scope of this report to explore this issue,
it certainly requires consideration.
The concrete industry may see innovations that
will change the GHG-intensity of their products.
CO2 injection has been shown to reduce GWP by
4-6 percent30 (on top of reductions available via
cement substitution noted above) and is available
on the market now. The use of captured CO2 to
make aggregate could result in concrete that stores
more carbon than it emits.31 The use of biochar as an
aggregate can similarly reduce the MCE of concrete.
Policy makers and builders will want to keep up with
developments in this field as they could dramatically
remake the emissions map for new homes.
Today’s best available concrete
could eliminate 2,500 tons of
emissions from new home
construction annually.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 28
XPS Foam Board R 5/inch
Aerogel Batt R 9.6/inch
Closed Cell Spray Foam (HFC) R 6.6/inch
NGX Foam Board R 5/inch
Vacuum Insulated Panel R 30/inch
Mineral Wool Board R 4.2/inch
Closed Cell Spray Foam (HFO) R 6.6/inch
EPS Foam Board (Type II) R 4/inch
Polyisocyanurate Foam Board R 6.5/inch
Open Cell Spray Foam R 4.1/inch
Mineral Wool Batt R 4/inch
Wool Batt R 4/inch
Fiberglass Blown In R 2.6/inch
Fiberglass Batt R 3.6/inch
Hemp Fiber Batt R 3.7/inch
Cellulose R 3.7/inch
Wood Fiber Batt R 3.9/inch
Hempcrete R 2.1/inch
Wood Fiber Board R 3.4/inch
Straw Bale R 2.8/inch
-2000 0 2000 4000 6000
Insulation Emissions Comparison for 100 m2 @ R5
4937
1652
1159
715
654
473
366
288
252
146
115
114
88
59
-70
-202
-218
-554
-663
-753
Each result is an
AVERAGE of a range
and products can vary
by as much as 50%
kg CO2e
3.2.2 Insulation
Insulation accounted for 5,242 tonnes of emissions in
the study, representing 26.1 percent of all measured
MCE. As the second highest impact category,
addressing emissions from insulation is clearly
important.
A leading strategy for reducing MCE in homes is to
design to use less material. But with increasing (and
important) demands for improvements in home
energy efficiency to reduce operational emissions,
new homes will likely be using more insulation, not
less. So as we push to improve energy performance
we risk driving the significant MCE from insulation
ever higher.
The MCE of insulation products varies widely. There
are 20 different insulation types in BEAM, many with
multiple product brands or options. Figure 11 shows
the average results for each type of insulation at the
same level of thermal performance. While direct
substitutions between products in Figure 11 cannot be
simply assumed, due to differences in performance
characteristics, there is an order of magnitude of
difference between the emissions of the options. It
is important to note that within a particular material
type, the carbon emissions for specific products made
can vary by over 50 percent (see Figure 11).
In some cases, a product with low emissions in
its category may have a lower R-value per inch of
thickness than another product with high emissions
in its category, meaning a greater quantity of the
product must be used to achieve an equivalent
R-value. For net carbon emitting insulations, this
generates higher emissions. Conversely, for net
carbon-storing insulations, this achieves greater
carbon storage.
Figure 11. Range of net emissions for different insulation types from BEAM soware.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 29
CONCRETE
32.9%
INSULATION
26.3%
CLADDING
13.3%INTERIOR
SURFACES
10.1%FRAMING
6.8%WINDOWS
5.1%
ROOFING
2.2%
Complicating the substitution of insulation materials
is the different performance characteristics required
of insulation products in different assemblies of the
home. Foundation wall insulation is responsible for
the majority of all insulation-related MCE, mostly
due to the exterior application of rigid XPS foam.
One possible solution for reducing foundation wall
carbon emissions is to substitute exterior subgrade
insulation with appropriate interior blanket or batt
insulation with a lower carbon footprint. All insulation
substitutions must be made using the best available
building science principles.
Figure 12 shows the total impacts of different
insulation types, regardless of their position in the
building. There are different demands on insulation
products depending on their location in building
assemblies, and some types of insulation may be used
successfully in multiple locations in the building while
others may be limited to just one or two types of uses.
3.2.2.1 Carbon-storing Insulation
Of the insulations used in the buildings of this study,
only two carbon-storing materials (cellulose and wood
fiberboard) were used, which together stored just under
400 tonnes of plant-sequestered CO2e emissions. The
carbon storage of these two materials reduced the
overall insulation category impact by 7.0 percent, while
only contributing 2.0 percent to insulation emissions.
These materials are composed primarily of biologically-
produced matter, sometimes termed biogenic
material. The carbon storage these materials claim was
sequestered from the atmosphere by photosynthesis
and made into physical carbon-based matter during the
plant’s growth. (see Section 2.3.2).
Due to the high volume of insulation used in homes
(and the likelihood of increases in insulation volume
to meet new energy efficiency requirements), the
use of more carbon-storing insulation offers the
most potential to dramatically reduce overall MCE.
The potential results of using more carbon-storing
insulation are explored in Section 4.
XPS FOAM
BOARD*
4,581,864 kg CO2e
87%
FIBERGLASS
BATT
346,709
kg CO2e
7%
MINERAL
WOOL
BOARD
274,740 kg
CO2e
5%
SPRAY
POLYURETHANE
FOAM
199,888 kg CO2e
4%
SPRAY
POLYURETHANE
FOAM - OPEN CELL
68,999 kg CO2e
1%
OTHER
59,810 kg CO2e
>1%
Cellulose loose fill
-271,646 kg CO2e
- 5%
Wood fiber board
-7,091 kg CO2e
> -1%
*This figure is for “legacy
formula” XPS insulation.
As of 2021, federal law
requires a lower GWP
formulation which can
substantially reduce
this figure.
Figure 12. Proportion of
insulation emissions by
product type.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 30
Figure 13. BEAM results for cladding
Brick
Acrylic Stucco
Aluminum Panel - 22 gauge
Fiber Cement - 5/15”
Steel Panel - 24 gauge
Lime Plaster (NHL) - 3/4”
Vinyl - 0.040”
Polypropylene - 0.085”
Lime/Cork Plaster - 3/4”
Engineered Wood - 5/16”
Wood (Cedar) - 3/4”
Wood (SPF) - 3/4”
Clay Plaster - 9/16”
kg CO2e/100m2 0 1000 2000 3000 4000 5000
Cladding Emissions, kg CO2e/100m2
4725
3500
1953
1703
1496
957
538
487
356
278
172
120
88
3.2.3 Cladding
The cladding category had the third highest emissions
impact, with 2,575 t CO2e representing 12.8 percent
of the total MCE in the study. Figure 13 shows the
relative emissions for the cladding options included in
the BEAM tool.
Cladding is a relatively straightforward material
category, with each option available in the BEAM
tool having met all testing requirements for the
purpose and most having long histories of use in the
region, which should make direct substitutions a
viable option. However, cladding is a material with
a high aesthetic impact for a home – as well as major
differences in durability and maintenance – and
substitutions on the basis of emissions alone may
not overcome decisions based on the desired visual
appearance of the home.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 31
CONCRETE
32.9%
INSULATION
26.3%
CLADDING
13.3%INTERIOR
SURFACES
10.1%FRAMING
6.8%WINDOWS
5.1%
ROOFING
2.2%
There are not currently any commercially available
cladding options with significant net carbon storage,
though some wood products may eventually have
carbon storage attributed to them (see Section 2.3.2).
However, even without carbon-storing options, it is
possible to reduce emissions by orders of magnitude.
The GTHA region features brick as a common
cladding material. All of the GTHA representative
home plans sampled included brick cladding, except
for one. Brick is by far one of the most emission-
intensive cladding options, with the bulk of the
embodied carbon emissions arising either from the
kiln-firing of clay bricks or the cement content of
concrete bricks.
While no low-emission brick products are currently
available in the GTHA, it is worth noting that US
manufacturer CalStar Brick issued an EPD for their fly-
ash brick product that would have 472 kg CO2e/100
m2, or one tenth of the emissions of typical bricks. If
this brick substitution were made in all the buildings
in this study, it would eliminate 1,200 t CO2e of
embodied carbon32, the same carbon reduction as
achieved by switching all 0-25 MPa concrete to the
lowest carbon mix available, as discussed in Section
3.2.1 .
The testing of bricks using biochar as a high volume
ingredient has demonstrated net carbon storage that
would equate to -1,778 kg CO2e/100 m2 in a cement/
biochar brick of typical thickness.33 This is an average
reduction of 138 percent from the MCE of bricks
used in this study’s sample buildings. If this biochar
brick were hypothetically substituted for all brick
cladding in the sample homes, it would result in the
net carbon storage (i.e. negative emissions) of 500
tonnes of CO2e, approximately one tonne per home
on average.
Until such low-carbon or carbon-storing brick
replacements become available, a move to any other
cladding choice that is under 1000 kg CO2e/100
m2 would reduce emissions by at least 75 percent
in this category. This includes using siding made
of vinyl, polypropylene, wood, and engineered
wood, and/or non-cement based plasters such as
lime and clay plaster. Aer biochar bricks, the lowest
emission cladding option is clay plaster at a mere 88
kg CO2e/100 m2. Clay plaster has 98 percent lower
carbon emission than the industry average brick
emission of 4,725 CO2e/100 m2.
BRICK
2,504,725 kg CO2e
98.1%Vinyl Siding 0.9%
Fiber Cement Siding 0.5%
Metal Panel Siding 0.5%
Wood Siding 0.1%
Figure 14. Carbon emissions of cladding by type for
all 503 as-built homes studied.
4. Effects of Material
Substitutions on MCI
The results of this study indicate that material selections for new
home construction can have a dramatic impact on material carbon
emissions. To explore the potential extent of MCI reductions based
on material selection, the researchers applied material substitutions
in the BEAM models in areas where material impacts were shown to
be highest.
The homes with the lowest and highest34 MCI results were selected
for material substitutions to examine whether any reductions might
relate to the overall design of the building or the as-built material
selections. Two new BEAM models were created for both samples.
The first scenario focuses on materials that could feasibly be selected
by builders today to explore how low MCI could go in the immediate
future, while the second scenario is intended to demonstrate the
possibilities for MCI reduction in the next 5-10 years.
4.1a Best available materials
(BAM) substitutions
Substituted materials were chosen to
ensure that they are readily available
in the GTHA marketplace and meet
all current code requirements. Two
kinds of substitutions were made in this
model: switches to new material type
and switches to best-in-type materials
(ie. brand-specific change). These
substitutions were chosen to reflect as
much similarity in product application
as possible (ie. if batt insulation was
selected for the as-built model, another
batt insulation was chosen to substitute)
to ensure that substitutions would be
practical for real-world applications.
In the BAM model, major substitutions include:
Concrete selection was changed from the Canadian benchmark
average of 305 kg CO2e/m3 to the lowest emitting mix from the
Canadian average EPD (Mix #19 at 214 kg CO2e/m3), as this type of
mix should be available from regional suppliers.
Insulation was changed to cellulose batts (for walls) and loose-blown
cellulose (for attics).
Cladding was changed from brick to the lowest emitting low-
maintenance option, engineered wood.
Minor substitutions include:
Carpet flooring changed to best available option
Hardwood flooring changed to linoleum
Drywall changed to best available brand
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 32
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 33
4.1b Best possible materials (BPM) substitutions
Materials were chosen to reflect the best possible emission results, regardless of whether or not the materials
are market-ready. All materials are commercially available in other markets, and have demonstrated code
compliance in those jurisdictions. Though this does not guarantee that such materials can be substituted in the
GTHA currently, it indicates a likelihood that this should be possible with adequate testing. Such substitutions
may require design changes and worker retraining for installation.
In the BPM model, major substitutions include:
Concrete selection was changed from the Canadian benchmark
average of 305 kg CO2e/m3 to 150 kg CO2/m3, an average of the two
best product-specific EPD results in Canada. While not necessarily
widely available, this type of mix requires no new technology and
should be able to be produced in the region.
Insulation was changed to straw-based material, based
on baled straw wall insulation and loose-blown chopped
straw insulation available in Europe.35
Interior walls were changed to compressed straw board,
based on modular interior partition systems available in
Europe and Australia.36
Cladding was changed from brick to
the lowest emitting low-maintenance
option, engineered wood.
Windows changed from vinyl
frame to wood frame with
aluminum cladding
Interior drywall was changed to
sheets of compressed recycled
drinking boxes, based on products
available in the USA and Europe.37
Flooring was changed to a mix of
linoleum (for high-wear and wet
areas) and cork.
Some of these substitutions would
require new products to become
available in the regional market
and some efforts to both redesign
aspects of the home and retrain
crews to install new materials.
However, the existence of homes in
Europe and some examples here in
Canada38 using all of these materials
indicates the potential, and one with
significant emission implications, as it
changes new homes from a source of
emissions to a source of net
carbon storage.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 34
4.2 Results of material substitutions
The home with the lowest MCI in this study had an emissions
intensity of 116 kg CO2e/m2 based on heated floor area. This
result puts this home well under the weighted average of
189 kg CO2e/m2, for the same heated floor area critera. If
all new Part 9 GTHA homes matched the MCI achieved
by this as-built home, it could reduce the total carbon
emissions by as much as 465,850 tonnes, roughly a 55
percent reduction from the current estimated emissions. This
in itself would be a remarkable impact, equivalent to removing
approximately 100,000 cars from the road. It is worth noting that
this example was a typical townhouse unit from a large developer
that presumably did not intend to achieve a low MCI score when it
was designed or built. An MCI of 116 kg CO2e/m2 could therefore be
considered an easily achievable minimum target for conventional and
cost-competitive buildings.
Table 8 shows the results of the six BAM and seven BPM substitutions for
the model with the lowest MCI based on heated floor area.
NET CARBON EMISSIONS
by assembly [kg CO2e] Original model –
Lowest MCI BAM
Substitutions BPM
Substitutions
FOOTINGS & SLABS 4,002 2,718 1,677
FOUNDATION WALLS 11,825 7,971 1,335
STRUCTURAL ELEMENTS 808 808 808
EXTERIOR WALLS 514 -397 -3,221
PARTY WALLS 818 166 -1,204
EXTERIOR WALL CLADDING 2,077 235 122
WINDOWS 1,285 1,285 800
INTERIOR WALLS 965 908 -6,357
FLOORS 3,250 1,593 838
CEILINGS 268 251 -1,061
ROOF 2,742 -242 -7,947
GARAGE 4,485 823 -1,361
NET TOTAL MCE 33,039 16,120 -15,571
NET MCI OF HEATED AREA (kg CO2e/m2)115.8 56.5 -54.6
% CHANGE FROM INITIAL -51% -147%
Table 8. Comparison of results for material substitutions for lowest MCI home (based on heated floor area).
The six BAM substitutions result in a reduction of MCI to 56.5 kg CO2e/m2, a 51 percent reduction from
as-built emissions. The substitution of seven Best Possible Materials (BPM) provides an encouraging result:
a home with net carbon storage in the measured materials, rather than emissions. The result of -54.6 kg
CO2/m2 is a 147 percent reduction from the as-built model.
51%
REDUCTION
in carbon emissions
Material Subsitution
=118%
REDUCTION
in carbon
emissions
Possible
NOW
REDUCTION
in carbon emissions
Possible
SOON
147%
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 35
A home with high MCl was given the same set of material substitutions as the low MCI model.
The results in Table 9 show that despite the higher initial MCI of 262.1 kg CO2e/m2, the BAM
substitutions actually reduced this model’s emissions by 196.6 kg CO2e/m2, a 75 percent
reduction.
NET CARBON EMISSIONS
[kg CO2e] Original model –
Highest MCI BAM
Substitutions BPM
Substitutions
FOOTINGS & SLABS 5,793 4,648 3,093
FOUNDATION WALLS 36,805 7,805 2,030
STRUCTURAL ELEMENTS 1,349 1,349 1,349
EXTERIOR WALLS 12,481 -2,265 -9,076
EXTERIOR WALL CLADDING 10,756 1,105 806
WINDOWS 2,325 2,325 1,447
INTERIOR WALLS 702 660 -4,653
FLOORS 4,572 2,346 1,296
CEILINGS 533 437 -1,358
ROOF 1,648 1,276 -7,904
GARAGE 4,546 694 -1,662
NET TOTAL MCE 81,510 20,380 -14,632
NET MCI OF HEATED AREA
(kg CO2e/m2)262.1 65.5 -47.1
% CHANGE FROM INITIAL -75% -118%
Tabel 9. Material substitutions for second highest MCI home (based on heated floor area)
The BPM substitutions brought this home’s total
MCI to -47.1 kg CO2e/m2, a 118 percent reduction
from the as-built result. This represents nearly 100
tonnes of CO2e emissions eliminated from a 252 m2
single family home as a result of only seven alternate
material choices.
The similarity between the MCI results from BAM-
substitution (56.5 and 65.5 kg CO2e/m2) and BPM-
substitution (-54.6 and -47.1 kg CO2e/m2) indicates
that material selection can drastically reduce MCI,
regardless of home design, as the use of a similar
material palette results in similar MCI outcomes.
The similarity between the material substitution
results invites the calculation of a hypothetical
estimate of the potential impact of such substitutions
across all new Part 9 homes in the GTHA region.
Reducing the weighted average MCI of 192.6
kg CO2e/m2 (based on municipal data floor area
criteria) to the average BAM-substitution MCI of 80.1
kg CO2e/m2 (based on the same floor area criteria)
would result in approximately 573,000 t CO2e fewer
emissions annually in the GTHA. Achieving average
BPM-substitution results of -67.3 kg CO2e/m2 (again,
based on the municipal data floor area criteria)
would result in the reduction of roughly 1,065,000
t CO2e. In this hypothetical scenario, new Part 9
homes built in the GTHA would pass beyond net
zero carbon to store around 225,000 tonnes
of carbon from the atmosphere during a single
construction year.
51%
REDUCTION
in carbon emissions
Material Subsitution
=118%
REDUCTION
in carbon
emissions
Possible
NOW
REDUCTION
in carbon emissions
Possible
SOON
147%
What does it cost
to reduce MCE?
Though it was outside the scope of this report
to comment accurately on the cost implications
of material substitutions, correspondence with
several regional concrete suppliers indicated
that a low-carbon concrete mix substitution
would not have any notable cost implications.
Pricing from HomeAdvisor.com shows average
installed prices for brick are $9-28 per square
foot, compared to $7-12 for engineered wood.
Cellulose insulation priced from three major
Canadian retailers was less expensive than the
as-built options, though installation costs may
vary. On the whole it is encouraging that the
most impactful substitutions on emissions do
not appear to have significant negative cost
implications and could potentially cost less. This
factor would be valuable to study in more detail.
In the near future,
new Part 9 homes built in the
GTHA could pass beyond net
zero carbon to store around
225,000 tonnes of carbon from
the atmosphere during a single
construction year.
4.3 A carbon-storing future?
The BPM substitutions in this study had a dramatic impact
on MCE, completely reversing the impact of home
building materials measured in this study from a source of
emissions to a potential pool of net storage. As selected
for this study, the BPM category only included materials
for which commercially available options exist in other
markets. Carbon-storing materials that are currently in
R&D would offer even further potential for net storage.
Should a concerted effort be made to encourage the use,
distribution and development of carbon-storing materials –
including promising materials like carbon-storing concrete
aggregate and biochar-based materials – it may be
possible to achieve even more net carbon storage than this
study indicates.
The home building sector may be unique in the potential
for a relatively rapid transformation from a major source of
GHG emissions into a zero-carbon or even carbon-storing
sector. Combining the best efforts underway to achieve
zero emissions in operations and the use of carbon-storing
materials could result in the elimination of emissions from
this sector.
4.4 No changes to home designs
This study did not examine the impact of design changes,
such as moving space currently below grade to become
above grade (either fully or partially), massing changes,
solar orientation, window sizing, air tightness or
mechanical systems. Any or all of these types of design
changes could directly impact the MCE and OCE
of the homes.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 36
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 37
Conclusions
MCE is Substantial
The climate emergency has dire consequences for everyone in the GTHA and will require effective mitigation
and adaptation efforts on behalf of every citizen and sector of the economy. Recognition of the importance of
climate impacts has led to the study of material carbon emissions (MCE), and as this study demonstrates, these
impacts are substantial.
The structural and enclosure materials calculated for the built sample plans in this study represent over 20,100
tonnes of CO2e emissions annually. This would represent roughly 840,000 t CO2e per year if extrapolated to all
new Part 9 housing starts in the GTHA.
5.1 MCE is more substantial
than reported in this study
While the materials included in this study represent
a large portion of MCE from new homes, the
excluded materials – such as mechanical, electrical
and plumbing systems, millwork, paints and
finishes – could add anywhere from 30-60 percent
more emissions to those calculated in this study.
That suggests that the total MCE for new homes in
the GTHA could be as high as 1.2 -2.1 Mt CO2e of
(potentially avoidable) emissions per year.
5.2 MCE for Part 9 renovations and other
building activities likely substantial
This study focuses on new homes that fall within Part
9 of the Ontario Building Code. The importance and
scale of MCE would grow considerably if renovations
to Part 9 buildings were included, especially in
light of the proliferation of subsidy programs for
retrofitting older homes to be more energy efficient.
The conclusions of this study regarding the high
emissions impact from insulation materials are
perhaps even more relevant when it comes to retrofits
where insulation is oen the main material category
being added. It is quite likely that a study of retrofit
MCE compared to OCE reductions would find that,
as with new buildings, the addition of high emission
insulation materials may result in more total emissions
over the next few decades, rather than the net
reductions that are intended by subsidies.
Part 9 commercial buildings may have higher MCE
than residential buildings, as they oen feature large
concrete slab floors and enclosure systems that use
steel framing rather than wood, which has a much
higher MCE. Frequent renovations and interior
upgrades to commercial buildings likewise represent
a potentially large pool of MCE.
MCE from Part 3 (large) buildings exceed that of
the Part 9 buildings studied here with an average
of approximately 345 kg CO2e/m2, due to the high
volume use of impactful materials like concrete and
structural steel, and would likewise add to the total
MCE for the region.
5.3 MCE analysis should become
standard practice
The measurement of MCE for new homes should
become standard practice in order to collect more
accurate and complete data and help to drive
voluntary emission reductions and inform future
regulatory interventions. Tools such as BEAM (used
in this study) and Natural Resource Canada’s MCE2
are free and establish a common methodology for
estimating MCE particularly for Part 9 buildings, that
are relatively simple for policy makers, consultants,
designers, and builders to use. Technical training for
MCE calculation could be supported by regulators
and the industry to normalize the practice and
increase MCE literacy.
5.4 Carbon storing
materials are an important strategy
This study created updated versions of two model
homes (one with the low MCI and one with high)
to examine the impact of material substitutions on
overall emissions. The substituted materials that offer
net carbon storage (i.e. more atmospheric carbon
was stored in the materials than was emitted in
manufacturing; see Section 2.3.2) offset substantial
amounts of emissions from the other materials.
Using the best available materials (BAM) in six
categories, the carbon-storing materials reduced
MCI by 51 percent for the low MCI model and 75
percent for the high MCI model. Using “best possible
materials” (materials available in other markets but
not necessarily code compliant or in wide use in
the GTHA), the results were 147 and 118 percent
reductions, bringing the homes into net carbon
storage territory.
The “best possible materials” models do not include
carbon-storing material options that are currently in
development, such as concrete aggregate made from
captured carbon and bricks made with biochar. The
addition of these materials could offer a substantial
increase in the net carbon storage possible in a new
home.
Studying the cost implications of using more
carbon-storing materials was not within the scope
of this report. An initial exploration (see Sidebar XX)
indicated that costs would not necessarily be higher
for the BAM models, offering the possibility that
deep cuts in MCE are possible with reasonable cost
implications. Costs for the BPM models were difficult
to assess, as many of the material options are priced
for other markets and are not widely available in the
local region.
The opportunity for new homes to be sites of net
carbon storage rather than emissions offers a feasible
pathway for achieving the net zero emission targets
promised by national and regional governments.
The development and promotion of existing and
upcoming carbon-storing materials would be a crucial
factor in reaching net zero emissions in the home
building sector.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 38
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 39
5.5 Carbon Use Intensity (CUI) is an important
metric
Understanding the true climate impact of a new home
necessitates understanding all its related emissions
over a period of time. If a municipality or a building
company has time-related targets (ie. 50 percent
reduction in emissions by 2030, or net zero emissions
by 2050), then accounting for the emissions from
homes requires adding total MCE and OCE over that
period to ensure that goals are truly being met. This
is known as “carbon use intensity” (CUI), and is an
important lens for considering emissions from the
region’s homes.
5.6 Regional impact on Scope 3 emissions
Material carbon emissions (MCE) are not currently
included in municipal or regional inventories, as
they are the result of industrial and manufacturing
operations that typically happen outside the region
and as such are considered Scope 3 upstream
emissions. Despite the dispersed nature of the
emissions outside the boundaries of the region,
policy makers and builders in the GTHA can have
a major impact on these emissions, as the results
of this study indicate. Given the urgency to reduce
emissions globally, efforts to address MCE from new
homes constructed within the region can have a large
provincial, national and international impact even if
that impact is not on the “emissions ledger” for the
region.
Despite the urgency for immediate and measurable
climate action, effecting change in the home
building industry can be difficult, with competing
impacts of cost, aesthetics, material supply, labour
requirements, durability, performance and occupant
health all needing to be addressed within the scope
of the Ontario Building Code. MCE is a new factor
that needs to be considered in balance with other
demands. As policy-makers and builders have
different priorities and responsibilities, we offer the
following recommendations for addressing MCE that
are specific to both stakeholders.
As we work to
collectively reduce OCE
for homes in the GTHA, leaving
MCE unadadressed will miss the bulk
of a new home’s overall carbon use
intensity within the next crucial
next few decades.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 40
Recommendations for Policy Makers
6.1 Existing policy options
The researchers recommend that municipalities focus
on establishing appropriate metrics and measurement
for entire projects and avoid regulations that focus
on specific high-emitting materials. The complexities
of home building may dictate the need to use certain
high-emitting materials, and if these uses can be
offset by low-carbon and/or carbon-storing options
elsewhere in the building, net targets can still be
met. Additionally, innovation in material science
(such as carbon-storing concrete and new bio-based
materials) may turn options that currently have high
emissions into low emitters or even carbon-storing
materials.
Currently, neither the Ontario Building Code (nor the
National Building Code of Canada) address MCE.
The Ontario Building Code does offer a potential
doorway to the regulation of MCE in the form of
Objective OE1.1:
An objective of this Code is to limit the probability
that, as a result of the design or construction of
a building, the natural environment will
be exposed to an unacceptable risk of
degradation due to emissions of greenhouse
gases into the air.39(Emphasis added)
We recommend that GTHA municipalities request
that the Ontario government consider introducing
MCE requirements for Part 9 buildings in a future OBC
update, either via integration in the base code or
inclusion in an optional standard that municipalities
can opt into under section 97.1 (1) of the Ontario
Municipal Act. As noted above, we recommend any
potential OBC requirements be based on whole
project MCE/MCI metrics/targets rather than by a
prescriptive approach.
Support for such efforts might be enhanced by recent
developments in the regulation of operational carbon
emissions (OCE) in the British Columbia Building
Code. The province is also in early discussions with
leading municipalities to include MCE in the relatively
near future.
The City of Vancouver is embarking in early 2022
on the design of a program to reduce “embodied
carbon” (material carbon emissions) by 40 percent
by 2030. The report Policy Research on Reducing the
Embodied Emissions of New Buildings in Vancouver
contains excellent background information for
developing embodied carbon policies, and includes a
scan of global embodied carbon policies.40
The Cities of Nelson and Castlegar undertook the
Low Carbon Homes Pilot in 2021 “to enhance its
approach to reducing the impact of our buildings
by taking embodied carbon emissions (also referred
to as material carbon emissions) into consideration
alongside operational carbon emissions.41 The report
is intended to inform the development of a municipal
program to reduce MCE in 2022.
The City of Langford, BC, announced a “Low Carbon
Concrete Policy” in 2021, focused specifically
on reducing MCE from concrete. “Effective June
1, 2022, all concrete supplied to City-owned or
solicited projects, and private construction projects
greater than 50 cubic meters, will be required to be
produced using post-industrial carbon dioxide (CO2)
mineralization technologies, or an equivalent which
offers concrete with lower embodied CO2.”42
In Ontario, the Township of Douro-Dummer instituted
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 41
the voluntary “Sustainable Development Program”
in 2020. This program offers a “40 percent permit
fee rebate on all approved projects that meet the
required greenhouse gas reduction targets, or an 80
percent permit fee rebate with combined with net-
zero ready construction”43 and is the first program
in North America to measure MCE and provide
incentives for reductions.
Similarly, tier 2 of the Toronto Green Standard for
low-rise residential projects (version 4) includes
a requirement to meet an MCI target of 250 kg
CO2e/m2 or less. Tier 2 is voluntary, but incentivized
via a significant development charge refund. The
City of Toronto is currently exploring potential to
integrate MCE requirements in the mandatory tier
1 requirements in a future update to the Toronto
Green Standards. This general approach of starting
with municipal incentives for limiting MCE, and
subsequently exploring a transition to municipal
requirements, has the advantage of building industry
familiarity with low MCE approaches in advance of
future provincial and/or municipal regulations.
This report recommends an approach that uses an
MCI “carbon cap”. Part 9 homes share a relatively
consistent design and construction approach, and as
evidenced by this study, the MCI results fall within a
reasonable close range. With sufficient stakeholder
input, it should be feasible to agree upon targets
for voluntary MCI “absolute targets” and to further
incentivize builders who meet more stringent
targets. The broad sample size of this study might
be considered sufficient to establish such a cap or
threshold.
The researchers discourage creating policies or
programs that use baseline results as a benchmark
for MCE/MCI reductions. As seen in Section 4.2, it is
possible for homes with different designs to achieve
very similar MCI results based on material selection,
but that starting with a higher baseline would allow a
home to show a very large percentage of emissions
reduction without achieving low results.
6.2 Municipal EPD requirements
The researchers recommend that GTHA municipalities
consider signaling an intention to first prefer and
then, aer a reasonable time, require Environmental
Product Declarations for all construction materials
used in municipal construction projects in order to
encourage all manufacturers to begin producing
product-specific EPDs. Increased product
transparency would result in more complete and
accurate data for tools that measure MCE. This is
particularly true for concrete, where variations in
emissions from different manufacturers and/or mixes
can affect MCE by as much as 100 percent.
6.3 Metrics for MCE programs
The researchers recommend that GTHA municipalities
work to establish bold MCE metrics and caps/
thresholds that bring about staged emission
reductions over time. Following a similar strategy to
the energy step codes in British Columbia, all homes
would be required to meet the current target and
incentives applied to encourage projects to meet the
future higher targets earlier.
The choice of a metric for a relatively new field
like material carbon emissions sets an important
precedent that may be difficult to change, once
established. It is possible to cause unintended
consequences in choosing a metric. As seen in the
results of this study, there is a significant difference
between MCI calculated on gross floor area and
habitable floor area. The use of habitable floor area
as a basis for MCI deters homes from having large
garages and/or unfinished basements, since the
MCE arising from these materials is attributed to the
habitable area, pushing MCI up by 32 percent in the
samples studied. For this study, this decision was
made as an effort to prioritize emissions based upon
serving residents over space for cars and storage.
Municipalities seeking to incentivize reductions or
regulate MCE could seek a metric that serves other
priorities. The researchers experimented with a
number of alternative metrics that could balance
MCE with building size and number of bedrooms as a
proxy for number of occupants “sharing” the carbon
emissions of a house. While these priorities may
not align with those of each GTHA municipality, we
encourage policy makers to clearly identify priorities
that might be combined with MCE to bring about the
desired impacts.
One potential metric to consider is known as “carbon
use intensity” (CUI). This metric combines the material
carbon emissions of a house with the anticipated
operational emissions over a defined period of time.
Choosing a timeframe that matches the climate
targets of a municipality enables policies to be aligned
with overarching targets. For example, a metric of
CUI2030 would include the MCE of a home and all
operating emissions until 2030. If the municipality’s
overall goal is 40 percent reduction in emissions by
2030, then the CUI2030 would need to be 40 percent
less than today’s benchmark.
CUI is a useful metric, as it allows for flexibility for
municipalities and builders to meet the CUI threshold
in different ways, concentrating on electrification,
improved materials and/or energy efficiency to
degrees that are practical and meet local needs.
As noted in NRCan’s Achieving Real Net Zero
Emission Homes, “the Carbon Use Intensity metric
would enable more accurate accounting for GHGs
from the homebuilding sector, and would also
allow for regionally appropriate ways to reach CUI
targets.44 The GTHA region has already established
methodologies and inventories for the OCE from
homes, and this study provides a basis on which to
begin considering MCE so that the two metrics can,
ideally, be combined for new homes.
42
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 43
6.4 Incentives for reducing MCE
The researchers recommend municipalities explore
incentives with relatively low program costs and
complexity that enable municipalities to signal
leadership in MCE reduction and encourage the
building community to engage in MCE reductions.
Voluntary incentives have been used in municipalities
around the world to encourage early action on MCE
reductions. These incentives include:
Reduction in planning/permit fees and/or
faster timelines for approvals for projects
reporting MCE/MCI/CUI with submission
Reduction in planning/permit fees and/or
faster timelines for approvals for projects
voluntarily meeting a MCE/MCI/CUI cap/
threshold
Recognition/awards for projects meeting
a MCE/MCI/CUI cap/threshold and/or
projects with lowest recorded MCE/MCI/CUI
in category
“Low-carbon” designation offered to
projects and/or builders meeting a MCE/
MCI/CUI cap/threshold
6.5 Stacked benets for reducing MCE
The researchers recommend that municipalities
explore the additional opportunities that may exist
in conjunction with policies to reduce MCE and
include such benefits when proposing policies. GTHA
municipalities may be able to achieve numerous
stacked benefits from pursuing MCE reductions,
including:
Economic opportunities from new regional
manufacturing of low-carbon and carbon-
storing materials. The region has a large
supply of the raw materials required for
improved materials and the manufacturing and
transportation infrastructure to support.
Healthier indoor environments for building
occupants. Carbon-storing materials are
typically free of off gassing and dangerous
chemical content.45
Reduced landfill waste volumes. Carbon-
storing materials can more easily be diverted to
composting facilities rather than landfill.
Training opportunities for leading educational
institutions in the region. These include courses
and programs in low-carbon construction
at universities, community colleges and
private career colleges, educating architects,
engineers, home designers, builders and
tradespeople.
Conservation benefits from ecosystem services
provided by sustainably-managed resources for
biogenic materials.
44
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction
MCE and the City of Toronto’s Green Standard, V4
The Toronto Green Standard is Toronto’s sustainable design and performance requirements for
new private and city-owned developments since 2010. Version 3 has been in effect since 2018
and Version 4 comes into effect May 1, 2022 for new planning applications. The Standard consists
of tiers of performance with Tier 1 being mandatory and applied through the planning approval
process. Financial incentives are offered through the Development Charge Refund Program for
eligible and verified Tier 2 or better, high performance, low emissions projects.
The Toronto Green Standard Version 3, included a performance pathway to high performance, low
emissions new construction by 2030 based on absolute performance targets related to greenhouse
gas (GHG) emission limits, energy use intensity and thermal energy demand intensity. The staff
report and the City’s Zero Emissions Building Framework study that supported this change set out
a stepped approach to increasingly higher energy and GHG performance measures with each
Toronto Green Standard update for large Part 3 Buildings (which comprise over 85 percent of
projected new construction in Toronto).
In the TGS v4 (2022) a new voluntary requirement has been added for Tier 2 and 3 projects to
conduct a materials emissions assessment of the upfront embodied carbon of structural and
envelope components. This requirement recognizes the importance of the carbon footprint of
building materials and the role of the Toronto Green Standard in planning and decision making.
A requirement for Tier 2 projects to calculate the embodied carbon and the carbon sequestration
within landscape designs has also been added.
The researchers suggest that the TGS v4 could consider using the data from this study to
implement a Part 9 MCI threshold requirement for Tier 2 and 3 projects. The average MCI result
of approximately 190 kg CO2e/m2 (based on the ‘gross floor area’ definition used in municipal
reporting) represent an achievable threshold. Limiting the maximum MCI of homes to this
threshold would reduce emissions in the study by 14.3 percent across all new Part 9 homes in the
region.
“Stretch goals” for Tier 3 of the TGS could also be set to encourage greater innovation. 61 homes
in this study achieved MCI for heated floor area of less than 150 kg CO2e/m2, suggesting that this
may be an appropriate stretch goal. 28 homes had less than 125 kg CO2/m2 of heated floor area,
suggesting an even more ambitious stretch goal.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 45
Industry Recommendations
7.1 Measuring MCE
The researchers recommend that all new home
designs undertake early MCE measurements during
design development to lower emissions as much as
possible, and use MCE tools to ensure procurement
prioritizes the material brands with the lowest
MCE. Free tools such as BEAM and MCE2 enable
designers and builders to obtain MCE results for
projects with relative ease and simplicity.
7.2 Request EPDs from manufacturers
The researchers recommend that designers
and builders send requests to manufacturers
for product-specific EPDs. Increased product
transparency would result in more complete and
accurate data for tools that measure MCE and in
turn provide builders with more options.
7.3 Explore immediate potential for
material substitutions
The researchers recommend that builders seek to
implement all feasible 1:1 material substitutions
that can reduce overall MCE. Modeling home
designs with free tools such as BEAM and MCE2
offers opportunities to compare the MCE for
materials that can be easily substituted for
one another.
7.4 Plan for future material substitutions
The researchers recommend that builders set
MCE/MCI/CUI targets that are achievable within
a 2-5 year window and begin design and supply
chain work to support such changes. Free tools
such as BEAM and MCE2 offer opportunities
to explore material options that may require
additional design and/or procurement changes in
order to use a material with lower MCE.
7.5 Examine design options
for reduced MCE
The researchers recommend that builders explore
design options that reduce MCE in addition to
directly substituting materials. While this research
did not directly address design options to reduce
MCE, the high impact of concrete suggests that
designs that minimize below-grade space and
reduce or eliminate concrete floor slabs will achieve
large MCE reductions, as will multi-unit homes
that share party walls and therefore require less
insulation. Further design analysis using MCE tools
could highlight other opportunities for reductions.
7.6 Declare and promote reduced MCE
The researchers hope that home builders will
undertake MCE modeling of their new homes, make
all efforts to reduce emissions and publicize their
achievements. The 52 percent of Canadians who
are extremely concerned or quite concerned about
climate change46 are among the customers for new
homes. New homes that can declare themselves to
be low-carbon or zero-carbon will be attractive to
such buyers.
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 46
Endnotes
1 IPCC report: ‘Code red’ for human driven
global heating, warns UN chief https://news.un.org/en/
story/2021/08/1097362
2 Pan-Canadian Framework on Clean Growth and
Climate Change (2017). Cat. No.: En1-77E-PDF ISSN: 2561-4169
https://www.canada.ca/content/dam/themes/environment/
weather/climatechange/PCF-FirstSynthesis_ENG.pdf
3 Canada’s Climate Actions for a Healthy Environment
and a Healthy Economy, 2021. https://www.canada.ca/en/
services/environment/weather/climatechange/climate-plan/
climate-plan-overview/actions-healthy-environment-economy.
html
4 Explanation: The “up front” emissions for buildings
include transportation to the building site and construction
activities, which are not included in this analysis. All of
the emissions in this study are directly associated with the
manufacturing of materials, so we use the term “material carbon
emissions”
5 Simonen, K., Rodriguez, B., McDade, E,. Strain, L.
(2017) Embodied Carbon Benchmark Study: LCA for Low Carbon
Construction. http://hdl.handle.net/1773/38017
6 Low Rise Buildings as a Climate Change Solution
(2019). Builders for Climate Action. https://www.
buildersforclimateaction.org/whitepaper1.html7
7 Magwood, C., Ahmed, J., Bowden, E., Racusin, J.
(2021) Achieving Real Net Zero Emission Homes. https://www.
buildersforclimateaction.org/uploads/1/5/9/3/15931000/
bfca-enercan-report-web.pdf
8 According to the National Building Code of Canada,
each of the five energy performance tiers have two compliance
metrics, overall percent improvement and heat loss reduction.
Both of these are calculated in terms of percent improvement
over the Reference House based on minimum prescriptive
requirements. The targets for Tier 3 are 20 percent overall
improvement and a 10 percent reduction in gross space heat loss.
9 Establishing the Average Up-Front Material Carbon
Emissions in New Part-9 Residential Home Construction in the
City of Nelson & the City of Castlegar (2021). https://www.
nelson.ca/DocumentCenter/View/5586/Benchmarking-
Report?bidId=
10 Residential Housing Stock and Floor
Space, NRCan (2018). https://oee.nrcan.gc.ca/
corporate/statistics/neud/dpa/showTable.
cfm?type=HB&sector=res&juris=00&rn=11&page=0#sources
11 Negative emissions or carbon dioxide removal (CDR) “is
the removal of greenhouse gases (GHGs) from the atmosphere by
deliberate human activities, i.e., in addition to the removal that
would occur via natural carbon cycle or atmospheric chemistry
processes” according to IPCC, 2021: Annex VII: Glossary
[Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V.
MassonDelmotte, C. Méndez, S. Semenov, A. Reisinger (eds.)]
12 Residential Housing Stock and Floor
Space, NRCan (2018). https://oee.nrcan.gc.ca/
corporate/statistics/neud/dpa/showTable.
cfm?type=HB&sector=res&juris=00&rn=11&page=0#sources
13 Milton floor area averages, determined by examination
of data from Milton.
14 International Organization for Standardization.
(2017). Sustainability in buildings and civil engineering
works ; core rules for environmental product declarations of
construction products and services. https://www.iso.org/obp/
ui/#iso:std:iso:21930:ed-2:v1:en
15 Archtoolbox: Environmental Product Declarations
(EPDs): A Guide for Architects. https://www.archtoolbox.
com/materials-systems/sustainability/environmental-product-
declarations.html
16 Additional emissions from the installation and/or use
phases of a product are included (and noted in BEAM) in cases
where emissions are significant and arise from the product’s
material itself and not the installation period, so that regardless
of the specifics of the installation, a quantifiable amount of
emissions will occur. These additional emissions are typically from
direct off-gassing of GHGs from the product during construction
and/or occupancy of the home.
17 ECN Phyllis Classification. https://phyllis.nl/Browse/
Standard/ECN-Phyllis
18 An equivalence factor between CO2 avoidedemissions
and sequestration.Pedro Moura Costa, Charlie Wilson. (2000)
Environmental Science Mitigation and Adaptation Strategies for
Global Change. DOI:10.1023/A:1009697625521
19 Adapted from Srubar et al., A Methodology for
Building-Based Embodied Carbon Offsetting (2021) https://
www.aureusearth.com/documents
20 https://www.istructe.org/IStructE/media/Public/
Resources/istructe-how-to-calculate-embodied-carbon.pdf ,
https://www.leti.london/ecp
21 Life Cycle Assessment of Mechanical, Electrical, and
Plumbing in Commercial Office Buildings. Carbon Leadership
Forum (2019). https://carbonleadershipforum.org/office-
buildings-lca/
Builders for Climate Action & Passive Buildings Canada • Emissions of Materials Benchmark Assessment for Residential Construction 47
22 Based on an average of acrylic interior paint EPD results
from Behr, Kelly Moore and Sherwin Williams EPDs collected in
2019.
23 US EPA, 2018, Greenhouse Gas Emissions from a Typical
Passenger Vehicle. https://www.epa.gov/greenvehicles/
greenhouse-gas-emissions-typical-passenger-vehicle
24 The Atmospheric Fund 2021. 2019-2020 Carbon
Emissions Inventory for the Greater Toronto and Hamilton Area.
https://taf.ca/wp-content/uploads/2021/12/TAF_Carbon-
emissions-inventory-GTHA_2021.pdf
25 Embodied carbon benchmarks for Part 3 buildings in
the Greater Toronto-Hamilton Area. https://drive.google.com/
file/d/13vU61c7_0UINI_LjzODykqAE0sXgNL9S/view
26 Magwood, C., Ahmed, J., Bowden, E., Racusin,
J. (2021). ACHIEVING REAL NET-ZERO EMISSION HOMES:
Embodied carbon scenario analysis of the upper tiers of
performance in the 2020 Canadian National Building Code. Pg
35.
27 New, Ontario-specific concrete EPD data is due to be
published in Summer, 2022
28 CRMCA member industry-wide EPD for Canadian ready-
mixed concrete, EPD10092. NSF (2017). https://info.nsf.org/
Certified/Sustain/ProdCert/EPD10092.pdf
29 https://www.buildingtransparency.org/ec3
30 CarbonCure’s Impact on the Global Warming
Potential (GWP) of Concrete. https://go.carboncure.com/
rs/328-NGP-286/images/CarbonCure%20Impact%20on%20
Global%20Warming%20Potential%20of%20Concrete.pdf
31 As an example, Blue Planet makes aggregate from
waste stream CO2 that the company claims mineralizes 440 kg of
CO2 per tonne of aggregate. https://www.blueplanetsystems.
com/
32 CalStar Brick SMaRT Environmental Product Declaration.
http://mts.sustainableproducts.com/CalStar%20EPD%20
Document_Final.pdf
33 Hans-Peter Schmidt, Kathleen Draper, Biochar building
material for a climate neutral future (2020). https://www.
mikrobihotelli.fi/wp-content/uploads/2020/10/Biochar-based-
building-materials.pdf
34 The researchers used the second-highest MCI sample,
as the highest MCI sample is a very large custom home and does
not represent a typical typology in the study.
35 Iso-Stroh blown-in insulation made from 100% wheat
straw. https://www.iso-stroh.net/
36 https://durrapanel.com/, https://kodukuubis.com/
en/about-straw-panel/, https://ekopanely.co.uk/, https://
coobio.com/
37 Continuus Materials Everboard. https://www.
continuusmaterials.com/, https://www.cmdgroup.com/
documents/FS/catalogs/ReWallCeilingTile_120612.pdf
38 Endeavour Centre. Zero House: A zero carbon, zero
net energy, zero toxin, zero waste prefab home (2017). https://
endeavourcentre.org/project/zero-house/?v=e4b09f3f8402
39 Ontario Building Code, O Reg. 332/12, s.2.2.1(1)
https://www.canlii.org/en/on/laws/regu/o-reg-332-12/latest/
o-reg-332-12.html#Part_2_Objectives_153709
40 Zahra Teshnizi, Policy Research on Reducing the
Embodied Emissions of New Buildings in Vancouver (2019).
https://vancouver.ca/files/cov/cov-embodied-carbon-policy-
review-report.pdf
41 City of Nelson, Low Carbon Building Materials (2022).
https://www.nelson.ca/905/Low-Carbon-Building-Materials
42 City of Langford Announces Bold, Low Carbon Concrete
Policy (2021). https://www.langford.ca/city-of-langford-
announces-bold-low-carbon-concrete-policy/#!
43 Township of Douro-Dummer, Sustainable Development
Program (2019). https://www.dourodummer.ca/en/building-
and-renovating/sustainable-development-program.aspx
44 Magwood, C., Ahmed, J., Bowden, E., Racusin,
J. (2021). ACHIEVING REAL NET-ZERO EMISSION HOMES:
Embodied carbon scenario analysis of the upper tiers of
performance in the 2020 Canadian National Building Code. Pg.
32.
45 Magwood, Chris. Opportunities for CO2 Capture
and Storage in Building Materials (2019). Pg 61. DOI: 10.13140/
RG.2.2.32171.39208
46 Abacus Data, Recent extreme weather has more
Canadians worried about climate change’s impact on their health
(2021). https://abacusdata.ca/extreme-weather-climate-change-
choices/
ResearchGate has not been able to resolve any citations for this publication.
Thesis
Full-text available
The “upfront” embodied carbon (EC) of building materials includes the accumulated greenhouse gas (GHG) emissions resulting from harvesting, manufacturing and transportation processes, and is becoming more widely recognized as a major source of global GHGs. The aim of this study is to demonstrate the potential for buildings to go beyond reduced or zero GHG emissions and to become– at least temporarily – a negative emissions technology, namely places of net storage of carbon. The study examines the EC for two samples of low-rise residential buildings that are representative of the North American wood-framed typology: a single-unit raised bungalow of 185m2 and an eight-unit, four-story of 935 m2. Data from Environmental Product Declarations (EPDs) for a wide variety of materials that could feasibly be used to construct the sample buildings are used to calculate the total EC for four different material assemblies in each building type: High EC, Typical EC, Best Conventional EC and Best EC. Results demonstrate the upfront embodied carbon can vary widely, ranging from a worst-case scenario of 415 kgCO2e/m2 of net emissions to a best case of 170 kgCO2e/m2 of net carbon storage by using biogenic (plant-based) materials. In addition, an energy modeling analysis of the buildings was conducted for the Toronto, Ontario climate to compare the EC with the operational carbon (OC) emissions. The results show that achievable reductions in EC could provide more than four times the overall GHG reductions than energy efficiency improvements to reduce OC between 2020 and 2050. The building model with both the lowest EC and OC is shown to have net carbon storage for several centuries. At the current scale of US residential construction, annual carbon storage in residential buildings as modeled could reach 30,000,000 tonnes, the equivalent of 10 coal-fired power plants. The immediate impact of large-scale GHG reductions from the use of carbon-storing materials is demonstrated to be worthy of consideration for the building industry and related policy makers.
Environmental Science Mitigation and Adaptation Strategies for Global Change
Environmental Science Mitigation and Adaptation Strategies for Global Change. DOI:10.1023/A:1009697625521
A Methodology for Building-Based Embodied Carbon Offsetting
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