Demonstrating Embodied Emission Reductions using the Housing Catalogue Designs

Prepared for: Natural Resources Canada (NRCan)

Prepared by: Builders for Climate Action (BfCA)

Date: April 24, 2026

• Executive Summary
  • Key Findings
  • Recommendations
  • Conclusion
• 1. Introduction
  • 1.1 Background and Context
  • 1.2 Purpose of the Study
  • 1.3 Overview of the Housing Design Catalogue
• 2. Methodology
  • 2.1 Design Selection Criteria
  • 2.2 Selected Housing Designs
  • 2.3 BEAM Tool Overview
  • 2.4 Scenario Framework
  • 2.5 Reporting Metrics
  • 2.6 Strategic Design Intervention Scenarios
  • 2.7 Cost Comparison Methodology
  • 2.8 Biogenic Carbon Storage Methodology
• 3. Results & Discussion
  • 3.1 Embodied Carbon Results by Design and Scenario
  • 3.2 Leading Drivers of Emissions and Reductions in Ontario
  • 3.3 Leading Drivers of Emissions and Reductions in Alberta
  • 3.4 Carbon Storage Potential
  • 3.5 Impact of Strategic Design Interventions
  • 3.6 Cost Comparison Findings
  • 3.7 Whole-Building Emissions Performance
• 4. Conclusions
• Glossary
• References
• Appendix A: Builder and Policy Briefs
• Appendix B: Embodied Emission Scenario Models
• Appendix C: Full Results by Design and Product Category

EXECUTIVE SUMMARY

Canada faces a dual challenge: a need to build significantly more housing while reducing the greenhouse gas emissions associated with that construction. CMHC projects that annual housing starts must nearly double, from roughly 245,000 today to 430,000-480,000 per year, to restore affordability to 2019 levels by 2035. Delivering that supply without compromising climate progress depends on how those homes are built.

This study analyzes embodied emissions in six designs from the Housing Design Catalogue (hereafter referred to as ‘the Catalogue’), three each from Ontario and Alberta. Using the BEAM (Building Emissions Accounting for Materials) tool, it evaluates how product specification choices affect embodied emissions, carbon storage, and cost across three scenarios:

• Scenario 1 represents common building practice, based on the prototypical technical drawing sets and the material assumptions used in the HOT2000 energy model templates provided for Catalogue designs.
• Scenario 2 substitutes commercially available low-carbon and carbon-storing products
• Scenario 3 explores emerging bio-based products with high carbon storage potential

The analysis focuses on product substitution rather than redesign, demonstrating what can be achieved within existing building plans, construction practices, and regulatory frameworks.

Key Findings

Most embodied carbon reductions cost little or nothing, and the exceptions are few and identifiable. Cost analysis of the Ontario and Alberta fourplexes shows that many of the largest reductions are cost-neutral or cost-saving compared to what they replace. In Ontario, the low-carbon design cuts embodied carbon by 25 percent, and the substitutions that reduce emissions save approximately $12,800 per building, or $3,600 with the two products specified for carbon storage included. In Alberta, the design cuts 22 percent at a net cost of approximately $14,000, concentrated in two bio-based items, cork flooring and cavity insulation, whose Canadian supply chains are still developing. The largest reductions in both provinces, led by low-carbon concrete, come at no additional cost.

Embodied emissions outweigh operational emissions through a new home's first 18 years. For that period, the Ontario fourplex modelled here emits more carbon in its materials than in its operation. Under the all-electric heating option the Catalogue already provides, the period extends to 49 years. Over 25 years, electrifying the heating system avoids more carbon than the material change does, but the operational curve can be bent later, as equipment is replaced and the grid decarbonizes, while embodied emissions are fixed on the day construction finishes. Material selection is therefore the more urgent decision, and the only one that cannot be revisited.

Immediate embodied emissions reductions of 14 to 26 percent are available today. Across all six designs, Scenario 2 reduced embodied emissions by an average of 23%, with no substantial changes to design, construction methods, or labour. The substitutions are for commercially available products moving through established Canadian supply chains.

A small number of products drive the bulk of emissions. Concrete, framing, insulation, and interior finishes account for a large share of Scenario 1 totals. In Ontario, concrete and framing alone represent about 40% of Scenario 1 emissions. Single substitutions in these categories can deliver 5 to 10 percent whole-building reductions, making targeted procurement an efficient and impactful strategy.

Higher energy performance does not have to mean much higher embodied carbon. Upgrading continuous insulation from R12 to R20 raises the insulation layer's embodied emissions by about 67 percent whichever product is used. Making the switch to the lowest-emission board at the same time more than halves the carbon cost of that upgrade, from 3.8 to 1.7 kg CO₂e/m². An emerging agricultural-fibre board delivers R20 at 36 percent below the emissions of the category-average product at R12.

Scenario 2 introduces meaningful carbon storage. Commercially available bio-based products contribute approximately 59 tonnes of biogenic carbon storage across the three Ontario designs and 47 tonnes across the three Alberta designs. This is durable stored carbon in building products at scale, achievable today through normal procurement channels.

Scenario 3 shows that all six designs can store more carbon than is emitted to build them. Emerging bio-based materials store approximately 185 tonnes of carbon across the Ontario designs and 234 tonnes across the Alberta designs. In every case, storage exceeds gross emissions and this stored carbon stays out of the atmosphere over the typical housing service life of 60 years, providing many decades of mitigation. These selections represent products that are manufactured at commercial scale elsewhere in the world, and the feedstocks to produce them domestically exist across Canada. These high carbon storage scenarios illustrate the carbon mitigation potential that targeted investment in Canadian bio-based manufacturing could unlock. At a nationwide scale, carbon storage at this level could be one of the largest climate mitigation strategies available in the near term and achievable while providing Canadians with durable, healthy homes.

Results are regionally variable but broadly consistent. Differences between Ontario and Alberta affect specific outcomes, particularly for concrete and insulation availability. But the overall pattern holds across both provinces: commercially available substitutions reduce emissions immediately, and emerging bio-based materials increase carbon storage substantially.

Additional reductions are available through material efficiency. Modest design changes can deliver further reductions. Foundation interventions tested on the Ontario Fourplex 01 reduced slab-related emissions by up to 57 percent, and a slabless plywood system achieved a 76 percent reduction on the slab assembly. These interventions often reduce both emissions and cost.

Implications

The results indicate that Canada does not face a fundamental trade-off between housing supply and climate goals. A substantial portion of embodied emissions from new housing can be addressed through specification and procurement decisions already feasible in current practice.

The Housing Design Catalogue provides a ready-made platform to implement those decisions at scale. The findings of this report and the Catalogue Materials Guide and energy model templates can be used together to identify specifications that can deliver measurable emissions reductions without new regulatory burdens and without waiting for code change.

The Scenario 3 findings reframe bio-based materials as a housing opportunity, not only a climate one. The feedstocks exist in Canada. The products exist globally. What is missing is domestic manufacturing capacity, supply chains, and approval pathways. Supporting these would turn Canadian housing into a durable carbon store while building a new low-carbon work force, much of it in the rural and agricultural regions where the feedstocks are grown. Deeper reductions will also require improved data, standardized measurement approaches, and continued development of dynamic lifecycle assessment methods to properly value biogenic carbon storage.

Recommendations

• Expand materials on low-carbon product sourcing opportunities. Build upon the findings of this study and the Housing Design Catalogue Materials Guide to provide more targeted information on low-carbon product sourcing opportunities. Disseminate this information to builders and designers, so lower-carbon options can be weighed alongside cost, performance, and availability.
• Integrate embodied carbon into policy frameworks. Include embodied emissions alongside energy performance in housing programs, procurement criteria, and future code development.
• Support domestic supply chains. Invest in manufacturing capacity, EPD development, and approval pathways for Canadian-made low-carbon and bio-based materials.
• Recognize carbon storage. Develop dynamic lifecycle assessment methods and policy mechanisms that account for durable biogenic carbon storage in building products.

Conclusion

The materials, tools, and knowledge required to reduce embodied carbon in housing already exist. This study shows that meaningful reductions can be achieved immediately, at scale, and without increasing costs. As Canada works to address its housing shortage, integrating embodied carbon into standard practice offers a practical path to delivering homes that meet both affordability and climate objectives.

1. INTRODUCTION

1.1 Background and Context

Canada faces an acute housing supply shortage. The Canada Mortgage and Housing Corporation (CMHC) has been quantifying the scale of the gap, and its latest analysis finds that annual housing starts must nearly double, from roughly 245,000 today to 430,000 to 480,000 per year, to restore affordability to 2019 levels by 2035.^{Footnote 1Footnote 2} Federal initiatives such as Build Canada Homes^{Footnote 3} signal the scale of response now being mobilized. Meeting that demand while reducing greenhouse gas emissions requires taking embodied emissions seriously.

Estimates of the building sector's share of Canada's emissions vary with what is counted. CaGBC estimates as much as 30% when construction is included,^{Footnote 4} while NRCan's inventory-based figures put the sector nearer 20%: roughly 18% from building operations, once the electricity buildings use is included, plus the embodied carbon of construction materials.^{Footnote 6} In Canada, material production, transport, and demolition generates roughly 28 million tonnes of GHG annually, about 4% of the national total.^{Footnote 6} This mirrors global findings on the climate impact of building materials.^{Footnote 5}

Because most embodied carbon is released before a building is occupied, these emissions are immediate and irreversible. In provinces with clean electricity grids, embodied carbon can represent over 80% of an all-electric new building's total lifecycle emissions through to 2050; even with carbon-intensive grids like Calgary's, it accounts for 48% by 2030.^{Footnote 7}

Canada's legislated commitment to net-zero emissions by 2050^{Footnote 8} is driving policy response across the building sector. The Greening Government Strategy commits to a 30% embodied carbon reduction on major federal construction projects starting in 2025, supported by mandatory disclosure and reduction requirements for ready-mix concrete and construction steel under the Standard on Embodied Carbon in Construction.^{Footnote 9} The National Model Code is expected to address embodied carbon in 2030,^{Footnote 10} a change that the Canada Green Building Council and others have actively advocated for.^{Footnote 11} Buy Canadian legislation creates new opportunities for domestic procurement of low-carbon materials.^{Footnote 12}

Canada is well positioned to act. The feedstocks and products needed to shift material specifications already exist, and many can be integrated into standard construction practice without changes to building methods or workforce training.^{Footnote 13} The Housing Design Catalogue offers an ideal platform to demonstrate this: by modelling material substitutions on real Catalogue designs, this study shows how housing delivery and climate goals can be advanced at the same time.^{Footnote 13Footnote 14}

1.2 Purpose of the Study

This study quantifies embodied carbon in six representative Catalogue designs across multiple material palettes and demonstrates how low-carbon and carbon-storing product substitutions can reduce emissions while maintaining performance and examining affordability issues. Because the Catalogue designs are complete and this study does not propose changes to the designs themselves, the focus is on product substitution rather than material efficiency: identifying lower-carbon and carbon-storing products that can be used with existing designs. Section 3.5 offers a limited number of minimal design changes to explore that reduction pathway.

1.3 Overview of the Housing Design Catalogue

The Housing Design Catalogue provides pre-designed, code-compliant building plans intended to accelerate housing delivery across Canada, with over 50 designs spanning ADUs, fourplexes, townhouses, and other missing middle formats.^{Footnote 15} Designs are adaptable to different lot sizes, regional conditions, and construction methods, and are intended as jumping-off points rather than prescriptive specifications, and leave many material selections to the user.^{Footnote 15}

To complement the Catalogue, CMHC commissioned a Materials Guide providing embodied carbon data, cost comparisons, and expected lifespans for commonly used building products.^{Footnote 17} The Catalogue drawing sets leave key material categories, such as cladding and cavity insulation, as placeholders for the user to finalize. Some assumptions used to fill those categories are set out in the supplementary energy and carbon models that accompany each design, and it is those modelled assumptions that this study takes as Scenario 1, the common-practice baseline against which the substitution scenarios are compared. Where the models leave room for choice, the Scenario 1 selections in this study align as closely as possible with assumptions made in the energy models and common building practice.

All Catalogue designs target National Building Code (NBC) 2020 Tier 3 energy performance, establishing a context in which operational emissions are being addressed.^{Footnote 15} This matters for the present study. As provincial electricity grids continue to decarbonize, the relative share of embodied carbon in a building's total lifecycle emissions will only grow; in clean-grid provinces it already dominates. The Catalogue's energy targets address the operational side; this study addresses the embodied side. Together, they position these designs to deliver on both housing supply and climate outcomes.

2. METHODOLOGY

2.1 Design Selection Criteria

This study analyzes six housing designs from the Housing Design Catalogue: two ADUs, two fourplexes, a stacked townhouse and sixplex. These typologies represent a few of the missing middle housing formats most central to Canada's supply response.^{Footnote 16Footnote 18}

ADUs have generated significant user interest in the Catalogue and represent a practical entry point for gentle density on existing lots, with manageable scale and construction complexity that makes them a natural starting point for demonstrating biogenic material viability.^{Footnote 19} Fourplexes align with recent zoning reforms supported through the Housing Accelerator Fund, which requires as-of-right zoning for up to four units on single-family lots as a condition of municipal funding.^{Footnote 11Footnote 20} The stacked townhouse and sixplex represent two different strategies for achieving the same density on a site, and are paired directly to enable that comparison.

The study focuses on Ontario and Alberta because the scale of anticipated construction in each province makes product-level embodied emission reductions particularly impactful, and because their different climate zones, grid carbon intensities, and foundation systems provide useful points of comparison.^{Footnote 2} Ontario designs are in Climate Zone 5 (Toronto), developed by LGA Architectural Partners. Alberta designs are in Climate Zone 7A (Edmonton), developed by Dub Architects. The Catalogue's energy models use a natural gas fired furnace as the primary heating scenario in both provinces, and this study follows that primary scenario. The Catalogue's mechanical sets also provide lower-carbon options in each region: the Alberta sets include a cold-climate air-source heat pump (ccASHP) with supplementary gas, and the Ontario sets include various hybrid and all-electric options. All use above-grade or at-grade floor systems, consistent with the Catalogue’s emphasis on accessibility.

2.2 Selected Housing Designs

Six designs were selected covering four typologies across Ontario and Alberta and are summarized in Table 2.2. Within each typology, one Ontario design is paired with one Alberta design to examine how regional conditions affect embodied carbon outcomes. Detailed specifications for all six designs are provided in Appendix B.

Table 2.2 Design Summary Comparison

Design Summary Comparison

Catalogue Name	Province	Gross Floor Area (m²)	Conditioned Area (m²)	Storeys	Bedrooms
ADU 02	Alberta	128	66	1	1
Fourplex 02	Alberta	431	371	3	12
Sixplex	Alberta	492	404	3	12
ADU 01	Ontario	59	50	1	1
Fourplex 01	Ontario	362	323	3	7
Stacked town 02	Ontario	711	630	3	15

2.3 BEAM Tool Overview

This study uses the Building Emissions Accounting for Materials (BEAM) estimator, developed by Builders for Climate Action, to model the embodied carbon of each design. The BEAM tool is inclusive of lifecycle modules A1 to A3 (the product stage), which represent roughly 65 to 85% of total lifecycle emissions for building materials.^{Footnote 21} BEAM generates material takeoff estimates using building dimensions and includes data from Environmental Product Declarations (EPDs) for a wide range of products available to home builders in Canada, including foundations, walls, floors, roofs, windows, cladding and finishes. Where no EPD exists for a product category, BEAM draws on peer-reviewed lifecycle assessments. For biogenic carbon, BEAM calculates carbon content using the Phyllis2 database for biomass quantification and applies a 10% reduction to total storage values to provide a conservative estimate.^{Footnote 22}

Each Catalogue design includes a Building Performance Report, publicly available through the Housing Design Catalogue website, developed using average embodied carbon values across the entire life cycle. This study takes a more granular approach via product-level EPD selection, and as a result will produce slightly different results for the same designs due to differences in system boundaries, EPD databases, and material quantity assumptions. These are normal sources of variation between modelling tools. The figures produced by any tool are estimates useful for comparison, not precise measurements, and this study's value lies in the consistency of its methodology across all six designs.

These variations also point to the need for a standardized approach to embodied carbon measurement in residential construction: consistent system boundaries, material scope, lifecycle stages, and data sources would allow results to be compared across projects and used to set meaningful targets. The recently published RESNET 1550-2025 Standard for Quantifying, Verifying and Reporting the Embodied Carbon of Buildings with Dwelling and Sleeping Units is an example of such a standard.^{Footnote 23}

2.4 Scenario Framework

This study models three scenarios for each design, covering the structure, enclosure, partitions, and primary interior finishes of each building, maintaining reasonable equivalent functional performance throughout. Appendix B provides the complete selection of products for each model and scenario and the details of the emissions and storage for each product along with totals per scenario.

Scenario 1: Common Practice

Scenario 1 represents common building practice for each design. Housing Design Catalogue drawings are intended to be near permit-ready but require the user to make decisions to finalize their design, including selecting elements left as placeholders in the drawing packages such as cladding and roofing materials, selecting manufacturers and products to be used during construction, and specifying elements not typically included within a building permit drawing set such as interior finishes. Where a drawing set does not name a specific product, Scenario 1 selections are drawn from the material assumptions used to prepare the HOT2000 energy model templates and Building Performance Reports that accompany each Catalogue design, supplemented by common practice in residential construction. Scenario 1 should be read as an assumption of common building practice based on the prototypical Catalogue designs, not as a specification contained in the drawing sets. It establishes the embodied carbon result against which the substitution scenarios are compared.

Material decisions rest with the user of each design, who should read this study alongside other Catalogue resources, including the design drawings, Materials Guide, Building Performance Reports, and Construction Cost Estimates. The scenarios are presented to illustrate how product choices affect embodied emissions, carbon storage, and cost.

Scenario 2: Commercially Available Lower-Carbon Products

Scenario 2 substitutes commercially available low-carbon and/or carbon-storing products accessible to builders through established Canadian supply chains, prioritizing like-for-like substitutions that require no substantial changes to design or construction practice. Product selections prioritize Canadian-manufactured options where possible and align with the Housing Design Catalogue Materials Guide.^{Footnote 17}

Scenario 3: Emerging Bio-based Products

Scenario 3 substitutes emerging products that are currently manufactured in a major global market and have published EPDs or preliminary LCA data. No effort has been made to ensure wide availability of these products in the Canadian market but all substitutions have precedents for use in Canada, often using alternative compliance pathways in building codes.

Scenario 3 points to what is possible to achieve in reduced embodied emissions and increased carbon storage with the support of government and industry, as outlined in the recent NRCan-funded paper ‘Building A Low Carbon Future: Exploring Feedstocks & Products For Canada’s Construction Sector’.^{Footnote 13} The feedstocks required to produce these products exist in abundance across the country, and the carbon storage potential the data demonstrates is precisely the argument for investing in the supply chains, EPD development, and policy conditions needed to bring them to market. This scenario establishes what becomes possible when that investment is made.

2.4.1 Product changes for scenarios

This study uses two distinct substitution strategies to model embodied emission reductions between the scenarios:

1. Procurement options highlight product selections within the same product category and focus on identifying types or brands with best-in-class embodied emissions. An example of a procurement option is replacing one dimensionally-identical drywall product with another. Such decisions will typically have no repercussions on the design or performance characteristics of the product and often little or no impact on cost.
2. Product substitution replaces one product type with a different one that can serve the same function, for example replacing fiberglass insulation with cellulose. Product substitutions can come with a variety of implications beyond embodied carbon and must be considered holistically. This study proposes many product substitutions based on real-world examples that demonstrate feasibility but does not raise performance considerations. Readers should not assume that these product substitutions are prescriptive changes that can be implemented without due consideration of the repercussions.

2.5 Reporting Metrics

Results in this study are expressed using three distinct metrics, each of which provides unique insights:

1. Total emissions and storage. This is the sum of gross results for every measured product in each building, showing the full extent of carbon emissions and carbon storage.
2. Intensity by conditioned floor area. Dividing total emissions and storage by the conditioned (habitable) floor area of each building provides a means of normalizing results across buildings of different sizes and typologies and can be useful for estimating emissions for similar but not identical buildings. Intensity results can also be applied to provide estimates for entire developments or regions.
3. Intensity by bedroom. Dividing total emissions and storage by the number of bedrooms identified on the plan set provides a proxy for examining emissions and storage as they relate to density.

There is no one correct or “best” metric to use when discussing embodied carbon, but intensity by conditioned floor gives the most consistent results between different building sizes and typologies and is therefore used commonly in this report and in discussions of embodied carbon more broadly.

2.6 Strategic Design Intervention Scenarios

In addition to the three main scenarios, this study examines the embodied carbon impact of two different design interventions: enhanced insulation and alternative foundation systems. Rather than remodeling all 18 designs, each intervention was analysed on the Ontario Fourplex 01 as a representative case, producing per-unit-area deltas that can be applied to any of the designs.

2.6.1 Enhanced Insulation

This variation tests the embodied carbon impact of upgrading continuous insulation on exterior walls from R12 to R20, a common energy performance improvement consistent with the trajectory of Canadian energy codes toward stricter NBC performance tiers. The analysis looks at the impacts of this change across three insulation products: conventional mineral wool board, wood fiber board, and ag-residue board.

2.6.2 Alternative Foundation Options

Foundations are among the highest embodied carbon assemblies in these designs, driven primarily by concrete and reinforcing steel. This variation models two alternative foundation approaches that reduce embodied carbon while maintaining equivalent structural performance and meeting accessibility requirements:

1. Thinner slab floor, reducing the Scenario 1 thickness of 6-inches to 4-inches where possible. Replacing flooring products over the concrete slab with paint/stain products is also considered.
2. Replacing the concrete slab with a plywood alternative, often called the “slabless slab.”

The embodied emissions of these options are reported, but they have not been included in the cost analysis due to the number of site-specific variables involved.

2.7 Cost Comparison Methodology

The cost comparison examines the product substitutions between Scenario 1 and Scenario 2, using substitutions that use the same installation method or require no substantial change to the labour requirements, allowing the material cost difference to be examined in isolation. For example, fiberglass batt insulation was changed to cellulose batt insulation rather than loose-fill cellulose insulation due to the unique labour characteristics of installing blown insulation compared to batts.

The cost analysis uses the Ontario and Alberta fourplexes as representative designs. Examining product changes in both provinces allows the study to reflect some regional differences in material pricing and product availability, since substitutions that may be straightforward in one market might require different costs and/or sourcing strategies in the other.

2.8 Biogenic Carbon Storage Methodology

Biogenic carbon is the atmospheric CO₂ absorbed by plants during growth and stored in plant-based building products for the life of the building, a benefit often referred to as carbon storage. Environmental Product Declarations (EPDs) report this as a negative emission, expressed in CO₂ equivalent (CO₂e) to match the units used for emissions.

Results in this study present gross embodied emissions and biogenic carbon storage as distinct results, rather than combining them into a single net figure. Although both emissions and storage are expressed as CO₂e, emissions figures report a GWP100 metric, indicating the global warming potential of all emitted greenhouse gases one hundred years from the occurrence of the emission(s). Storage is reported at the time of a biogenic feedstock entering a product. This significant difference in timing between the two results means that they cannot be directly compared, and reporting them separately avoids that mismatch.

Dynamic LCA offers a means by which the climate impact of emissions and storage could be directly compared. Research is currently being undertaken to develop appropriate methods and metrics for this type of reporting, including exploratory work by Natural Resources Canada.^{Footnote 24}

For the purposes of this study, the distinct results are analyzed uniquely to recognize the significant contribution to climate mitigation offered by carbon storage in durable building products without attempting to demonstrate equivalency.^{Footnote 25}

The climate value of this storage depends on the carbon remaining locked in the building over its service life. This study reports carbon stored at the point of construction (modules A1 to A3) and assumes the durable products that hold it remain in place over a typical housing service life of 60 years. What happens to that carbon at end of life, whether the products are reused, recycled, or landfilled, is outside the scope of this study and is one of the questions dynamic lifecycle assessment methods are being developed to address.

Due to the difficulties of ascertaining the climate impact of forestry and wood products, carbon storage has not been ascribed to products in this study that come from timber feedstocks.^{Footnote 24Footnote 26} Section 3.4 includes one scenario in which carbon storage for an engineered wood cladding product has been included in the analysis, to illustrate the impact this would have on total carbon storage.

3. RESULTS & DISCUSSION

This study creates a rich data set that includes whole-building outcomes, insights into emissions-intensive products and product categories, immediate and near-term carbon storage opportunities, design interventions, cost implications for emission reductions and the relationship between operational and embodied emissions.

The complete data set is shared in Appendix B to enable readers to generate insights that are not surfaced in this report.

3.1 Embodied Carbon Results by Design and Scenario

Table 3.1.1 presents overall embodied emission and carbon storage results using all three metrics. Every model demonstrates significant embodied carbon reductions and increases in carbon storage between Scenario 1 and Scenario 2. Most models demonstrate a continued reduction in embodied carbon emissions between Scenarios 1 and 2, with significant increases in carbon storage for all models.

It is worth noting that while the trends for emission reductions and increased carbon storage track with previous Canadian studies of embodied emissions, the Scenario 1 intensity results which range from 160 to 198 kg CO₂e/m² for this study (excluding the Alberta ADU, an outlier at 295 kg CO₂e/m² owing to its living-space-over-garage design), are lower than the average range of 186 to 223 seen in studies from Toronto, Vancouver and Nelson, BC.^{Footnote 27} These lower Scenario 1 results can be attributed to a couple of factors: there are no basement foundations in the Housing Design Catalogue and therefore lower quantities of concrete, and the carbon models assume cladding and cavity insulation products with relatively low embodied emissions. Brick cladding, in particular, is commonly specified in other studies and has very high emissions, as do other typical cladding products like stucco and manufactured stone. This leads the Scenario 1 results in this study to be at the lower end of the spectrum for typical Canadian housing.

Table 3.1.1 Embodied Emission Results by Project and Scenario

Embodied Emission Results by Project and Scenario

Project	Scenario	Emissions (kg CO2e)	Emissions Intensity by CFA (kgCO2e/m²)	Emissions Intensity per Bedroom (kgCO2e/bdr)	Storage (kg CO2e)	Storage Intensity by CFA (kgCO2e/m²)	Storage Intensity per Bedroom (kgCO2e/bdr)
Alberta ADU 02	Scenario 1	19,450	295	19,450	-	-	-
	Scenario 2	15,860	240	15,860	-6,754	-102	-6,754
	Scenario 3	21,124	310	21,124	-42,961	-631	-42,961
Alberta Fourplex 02	Scenario 1	60,306	163	5,025	-	-	-
	Scenario 2	47,293	127	3,941	-18,982	-51	-1,582
	Scenario 3	61,020	164	5,085	-89,571	-241	-7,464
Alberta Sixplex	Scenario 1	68,129	169	5,677	-	-	-
	Scenario 2	54,240	134	4,520	-20,986	-52	-1,749
	Scenario 3	67,580	167	5,632	-101,668	-252	-8,472
Ontario ADU 01	Scenario 1	9,880	198	9,880	-	-	-
	Scenario 2	8,526	171	8,526	-5,347	-107	-5,347
	Scenario 3	6,129	123	6,129	-13,480	-270	-13,480
Ontario Fourplex 01	Scenario 1	53,980	167	7,711	-	-	-
	Scenario 2	40,714	126	5,816	-17,464	-54	-2,495
	Scenario 3	34,190	106	4,884	-57,068	-177	-8,153
Ontario Stacked town 02	Scenario 1	100,594	160	6,706	-	-	-
	Scenario 2	74,461	118	4,964	-35,812	-57	-2,387
	Scenario 3	62,710	100	4,181	-114,705	-182	-7,647

It is valuable to note how the results change based on the metric observed. While the Ontario ADU has by far the lowest Scenario 1 result for gross emissions (9,880 kg CO₂e) it also has the second highest Scenario 1 intensity (198 kg CO₂e/m² conditioned floor area (CFA)) and the second highest Scenario 1 intensity per bedroom (9,880 kg CO₂e/bedroom). Also notable is the very high intensity result for the Scenario 1 Alberta ADU, which at 295 kg CO₂e/m² is 49 percent higher than the next highest result. This is due to the fact that this ADU design features living space over a garage, resulting in a high proportion of overall floor area that is not conditioned and therefore contributes to a higher burden on the intensity result.

Overall, the metric that provides the most consistent comparison is intensity by conditioned floor area, as this normalizes for building size and does not penalize for lower bedroom counts.

Table 3.1.2 Carbon Emissions Delta, per Design

Emissions Delta — Scenario 2 vs Scenario 1, by Project

Project	Province	Scenario 1 Emissions (kg CO₂e)	Sc2 Emissions (kg CO₂e)	Delta Sc2 vs Scenario 1 (kg CO₂e)	% Delta
ADU 02	Alberta	19,450	15,860	-3,590	-18%
Fourplex 02	Alberta	60,306	47,293	-13,013	-22%
Sixplex	Alberta	68,129	54,240	-13,889	-20%
ADU 01	Ontario	9,880	8,526	-1,354	-14%
Fourplex 01	Ontario	53,980	40,714	-13,266	-25%
Stacked town 02	Ontario	100,594	74,461	-26,133	-26%
ALL PROJECTS		312,338	241,094	-71,244	-23%

Table 3.1.2 illustrates the delta in embodied emission reductions from Scenario 1 to Scenario 2 reduces total emissions from a minimum of 14 percent for the Ontario ADU to a maximum of 26 percent for the Ontario stacked townhouse. The Alberta designs are clustered more closely, showing reductions of 19 to 22 percent across the three typologies. On average, the delta between the Scenario 1 and Scenario 2 models is 23 percent.

The 23 percent average reduction in embodied emissions between the Scenario 1 and Scenario 2 models indicates that a suite of commercially available product substitutions can be specified across these typologies and geographies to substantially lower the climate impact of new homes immediately.

Figure 3.1.3 uses the average embodied emission intensity of all three Ontario models to illustrate the emission reductions and storage increases available across the three design scenarios.

Figure 3.1.3 Average Embodied Emissions Intensity by Scenario - Ontario

Text version

Stacked column chart depicting the average embodied emissions intensity by scenario in Ontario. There are three scenarios along the x axis labelled from left to right. The y-axis demonstrates the kgCO₂e/m² conditioned floor area. Emissions intensity falls to 21 percent below the Scenario 1 baseline in Scenario 2, and 37 percent below in Scenario 3.

In Ontario, emissions intensity falls to 21 percent below the Scenario 1 baseline in Scenario 2, and 37 percent below in Scenario 3. Carbon storage grows alongside: from zero in Scenario 1 to a ratio of 0.5 tonnes stored per tonne emitted in Scenario 2, rising to 1.9 tonnes stored per tonne emitted in Scenario 3, averaged across the three designs. In Scenario 3, in other words, the volume of carbon stored in the building exceeds the volume of emissions released in producing it. A result of this kind invites dynamic LCA analysis to examine how the timing of storage and eventual end-of-life carbon release affects the building's net warming impact over time. As noted in Section 2.8, this study does not model that end-of-life stage; the storage reported here is the carbon captured at construction.

The Alberta designs follow a different pattern, shown in Figure 3.1.4. Emissions fall to 20 percent below baseline in Scenario 2, then return to about 2 percent above baseline in Scenario 3. This small rise reflects the fact that some emerging biomaterials in the Scenario 3 palette currently have higher manufacturing emissions than the conventional products they replace. This is common for new product categories: small-scale production has not yet yielded the efficiencies of scale that drive per-unit emissions down as an industry matures.^{Footnote 28} As manufacturing of these biomaterials expands, their production emissions are expected to decrease, and the Alberta designs should follow the Ontario pattern of reduced emissions alongside increased storage. The Alberta models demonstrate the same trend in the emissions to storage ratio, which increases from zero in the Scenario 1 model to 1:0.4 for Scenario 2 and 1:1.75 for Scenario 3, on the same average-intensity basis.

Figure 3.1.4 Average Embodied Emissions Intensity by Scenario - Alberta

Text version

Stacked column chart depicting the average embodied emissions intensity by scenario in Alberta. There are three scenarios along the x axis labelled from left to right. The y-axis demonstrates the kgCO₂e/m² conditioned floor area. Emissions fall to 20 percent below baseline in Scenario 2, then return to about 2 percent above baseline in Scenario 3.

3.1.1 Embodied emissions strategy

Taken together, these results demonstrate a clear two-stage opportunity to both significantly reduce embodied emissions and increase carbon storage in Canadian housing.

In the near term, the results for all six Scenario 2 models highlight an immediately accessible pathway to meaningful emissions reductions across all six designs, accompanied by a significant increase in biogenic carbon storage. These are both achieved using product substitutions that are widely available, meet Canadian building codes and standards, and would not require new labour practices. As explored in Section 3.6, many of these product substitutions do not require additional cost to achieve these sizable reductions in GWP and increases in carbon storage.

Scenario 3 points to what is possible in the coming decade if the Canadian home building sector strategically invests in emerging biomaterials. Such a strategy can double the emission reductions achieved in Scenario 2 and raise the volume of carbon storage substantially, to the point where every design demonstrates the potential to store more carbon than was emitted to build it. The two strategies are complementary, and the data suggests that the greatest gains are available by pursuing the development and uptake of products with low manufacturing emissions and high levels of carbon storage.

3.2 Leading Drivers of Emissions and Reductions in Ontario

Designers and builders can develop plans to reduce embodied carbon by focusing on the “hot spots” where a small number of products drive a high percentage of overall emissions from a building and provide the leading opportunities for reductions.

To examine the leading drivers of embodied emissions, the results from all three designs in each province have been summed to provide insights across the typologies. Tables that include a complete breakdown of all products used for each design can be found in Appendix B. For the purposes of this hot spot examination, the results of some product categories have been grouped where the same product is used in multiple assemblies in the design. Concrete and drywall are two leading examples where the same product appears in several different assemblies but the emissions of the building can be changed by making a single product substitution. Table 3.2.1 ranks the products with the highest total emissions in the Ontario designs. Following are examinations of the top seven emitting product types in Ontario and the context for achieving reductions.

Table 3.2.1 Emissions by Product Category - Ontario

Ontario — Emissions by Product Category (all designs combined)

	Scenario 1		Scenario 2		Scenario 3		Emissions Change vs Scenario 1
Product Category	Emissions (kgCO₂e)	Storage (kgCO₂e)	Emissions (kgCO₂e)	Storage (kgCO₂e)	Emissions (kgCO₂e)	Storage (kgCO₂e)	S1 vs BL (%)	S2 vs BL (%)
Concrete	33,001	0	24,570	0	25,530	-13,548	-26%	-23%
Framing	32,238	0	15,164	0	16,122	-47,499	-53%	-50%
Wall & Ceiling Finishes	18,277	0	12,490	0	15,008	-34,659	-32%	-18%
Windows	14,673	0	14,673	0	14,673	0	0%	0%
Cavity Insulation	14,440	0	18,792	-21,383	9,016	-44,472	30%	-38%
Continuous Insulation Above Grade	12,776	0	15,810	-29,259	3,521	-32,790	24%	-72%
Cladding	9,605	0	5,622	-5,504	6,404	-6,782	-41%	-33%
Continuous Insulation Below Grade	7,445	0	3,830	0	2,954	0	-49%	-60%
Flooring	6,863	0	4,145	-2,477	4,345	-5,504	-40%	-37%
Roofing	6,710	0	3,749	0	1,813	0	-44%	-73%
Membranes & Barriers	4,250	0	2,188	0	2,188	0	-49%	-49%
Structural Elements	2,964	0	1,453	0	1,453	0	-51%	-51%
Aggregate	1,211	0	1,211	0	0	0	0%	-100%
TOTAL	164,454	0	123,701	-58,624	103,029	-185,253	-25%	-37%

3.2.1 Concrete

As is typical for low-rise residential buildings, concrete is the leading driver of emissions, representing 20 percent of the total for the Scenario 1 model. This is a lower percentage than has been found in other embodied emissions studies in Canada, where concrete has commonly represented 35 percent of the total.^{Footnote 29} This is due to the inclusion of a high proportion of homes with basement-style foundations in other studies, whereas none of the designs in the Housing Design Catalogue designs include basements. Deeper foundations require more concrete, so the Housing Design Catalogue designs are an excellent illustration of the “use less material” strategy outlined in Section 3.3.

Emissions from concrete were reduced by 25 percent in the Scenario 2 models by the specification of a concrete mix with a high proportion of supplementary cementitious material (SCMs) that displace the use of Portland cement, the major contributor to concrete emissions. This single substitution represents a 5 percent reduction for the whole building. High SCM mixes are becoming more commonly available and used in Ontario, with some commercially available mixes achieving emission reductions of up to 50 percent^{Footnote 30}, double the assumption made in this study.

In Scenario 3, the emissions from concrete are slightly higher than in Scenario 2, despite the use of the same lower-carbon mix in the same quantity. This is due to the inclusion of two novel products: biochar concrete aggregate in the poured concrete [Solid Carbon] and CMU blocks made from algae-based cement [Prometheus Materials]. Both products are in small-scale commercial production in the USA. While these products do add a small percentage of additional emissions, they are responsible for a total of 13.5 tonnes of carbon storage. Building foundations have not typically been the site of carbon storage, and such products are able to introduce an additional 7 percent to the carbon storage totals of these models.

3.2.2 Framing

The Scenario 1 models of the Ontario Fourplex 01 and Stacked town 02 designs specify a high percentage of steel stud wall framing and the high emissions profile of steel is responsible for driving emissions to 32.2 tonnes, almost the equal of concrete. In Scenarios 1 and 2, the exterior wall framing is changed to typical wood stud construction, resulting in the highest category reduction percentage in Ontario at 53 percent. This substitution is responsible for a 10 percent overall reduction for the Scenario 1 model.

While steel framing is not uncommon in multifamily residential construction in Ontario, wood remains the predominant material for residential projects due to cost and familiarity with construction trades^{Footnote 31}, so the substantial reductions seen in this study would not be typical in many new homes which would be using wood stud framing by default.

The choice between steel and wood framing is typically governed by building code requirements for combustible or non-combustible construction, which depend on building type, size, and site conditions. The wood stud substitution modelled here is available only where combustible construction is permitted. Where non-combustible construction is required, reductions in this category would come instead from procuring best-in-category steel products.

3.2.3 Wall and Ceiling Finishes

The Ontario Scenario 1 models use gypsum board (or drywall) as the ubiquitous finish material for interior walls and ceilings. Although not a particularly high emitting product type, the sheer volume used in these models results in drywall being the third highest emitting product type. In Scenario 2, the models substitute drywall products with the lowest embodied emissions in their category, and this is enough to drive a 32 percent category reduction and 3.5 percent of the whole Scenario 1 model.

Scenario 3 substituted bio-based finishing panels for drywall, using average emission and storage results for three products currently manufactured in Europe (eelgrass, straw, and paper pulp panels). The emissions for these products is lower than drywall in Scenario 1 but slightly higher than the best-available drywall products in Scenario 2. However, these products add a substantial 34.6 tonnes of carbon storage to Scenario 3.

3.2.4 Windows

Windows were the fourth highest emitting products in the Scenario 1 model, and their embodied emissions remain constant across all scenarios. The glass panes are the biggest contributor to window emissions and double pane units were specified across all scenarios.

Manufacturer-specific EPDs for windows are less common than in other product categories, so this study uses average data for the wood framed, aluminum clad units selected for the Scenario 1. While the emissions profile for different window frame materials will be different, the lack of EPDs makes it difficult to specify a clear reduction opportunity at this time.

3.2.5 Cavity Insulation

Cavity insulation is the fifth highest contributor to GWP across the models, with fiberglass batts modelled in roof, floor, and wall assemblies in Scenario 1. Fiberglass is itself a relatively low-emission product; other common cavity insulation options have substantially higher emissions, including mineral wool batts (34 percent higher) and closed-cell spray polyurethane foam (71 percent higher), based on category average results. Had these products been modelled in Scenario 1, the Scenario 1 emissions for all six designs would have been meaningfully higher, which means the reductions achieved in Scenario 2 and Scenario 3 are conservative relative to typical Canadian construction practice.

In Scenario 2, a cellulose batt insulation product was selected to provide a batt-style alternative which would have similar installation requirements and timing. This product had slightly higher emissions, but also offered 21.3 tonnes of carbon storage. This product type is currently manufactured by one producer in the northeastern USA and could be produced by an Ontario-based cellulose insulation manufacturer.

A chopped straw cavity insulation was selected for Scenario 3, based on a product manufactured in Europe. This product offers the win-win of emission reductions of 5.4 tonnes and carbon storage of 44.4 tonnes.

3.2.6 Continuous Above-Grade Insulation

Much like cavity insulation, the wood fiber board product specified in Scenario 2 has a slight increase of 3 tonnes higher emissions than the Scenario 1 product, but offers 29.2 tonnes of carbon storage. The shift to the bio-based product specified in Scenario 3 achieves a similar win-win with lower emissions (9.2 tonnes) and higher storage (32.8 tonnes) than the Scenario 1.

3.2.7 Cladding

Cladding is much lower on the list of high emitters than in other Canadian studies, where it has typically been ranked the third highest emitting product category. The Scenario 1 products, a mix of engineered wood and metal panels, result in comparatively low emissions compared to other popular cladding products such as brick, stucco and manufactured stone. Only modest reductions were achieved in the cladding category, mostly due to sourcing metal stock for panels manufactured from very low-carbon steel.

In Scenarios 1 and 2, the biogenic carbon storage potential of the engineered wood product was included. Typically, carbon storage for timber products has not been included in this study, due to the difficulties of ascertaining the full climate impact of forestry and wood product supply chains. An exception was made for the engineered wood cladding product in Scenarios 1 and 2 to illustrate the contribution that timber-derived storage would make to total results should an appropriate consensus be reached on how such carbon storage claims should be considered.

3.3 Leading Drivers of Emissions and Reductions in Alberta

Table 3.3.1 provides a similar ranking of the product categories for the Alberta models from highest emitters to lowest. There are more similarities than differences between the two provinces, with some exceptions that are noted in the product summaries below. The differences between the product categories ranked second through fifth are minimal and do not indicate a meaningful difference in ranking.

Table 3.3.1 Emissions by Product Category - Alberta

Alberta — Emissions by Product Category (all designs combined)

	Scenario 1		Scenario 2		Scenario 3		Emissions Change vs Scenario 1
Product Category	Emissions (kgCO₂e)	Storage (kgCO₂e)	Emissions (kgCO₂e)	Storage (kgCO₂e)	Emissions (kgCO₂e)	Storage (kgCO₂e)	S1 vs BL (%)	S2 vs BL (%)
Concrete	45,524	0	38,292	0	39,175	-11,317	-16%	-14%
Wall & Ceiling Finishes	15,409	0	10,809	0	13,587	-39,211	-30%	-12%
Continuous Insulation Above Grade	14,413	0	15,037	-27,009	18,153	-24,059	4%	26%
Framing	13,823	0	9,705	0	24,524	-63,694	-30%	77%
Windows	13,573	0	13,573	0	13,573	0	0%	0%
Cavity Insulation	11,500	0	9,715	-16,346	12,975	-64,960	-16%	13%
Membranes & Barriers	8,845	0	6,200	0	5,554	0	-30%	-37%
Roofing	6,744	0	3,768	0	3,768	0	-44%	-44%
Flooring	6,436	0	2,785	-3,367	3,721	-3,365	-57%	-42%
Continuous Insulation Below Grade	4,615	0	2,336	0	1,546	0	-49%	-67%
Cladding	3,059	0	2,390	0	11,462	-27,594	-22%	275%
Structural Elements	2,690	0	1,530	0	1,530	0	-43%	-43%
Aggregate	1,218	0	1,218	0	155	0	0%	-87%
TOTAL	147,850	0	117,358	-46,721	149,723	-234,200	-21%	1.3%

3.3.1 Concrete

As with Ontario, concrete tops the list of emitters for the Alberta Scenario 1 models, representing 31 percent of total emissions. Two Alberta-specific factors shape the Scenario 2 result. First, Scenario 1 concrete in Alberta has a higher GWP than in Ontario. Second, the low-carbon mixes listed in the province-wide EPD contain lower percentages of supplementary cementitious materials (SCMs) than their Ontario counterparts. Together these factors produce a smaller emissions reduction in Scenario 2: 16 percent, compared to 25 percent in Ontario.

There are no technical performance reasons that higher SCM mixes cannot be viable in Alberta, suggesting that researching and promoting low-carbon mix designs could be a leading reduction strategy in the province.

3.3.2 Wall & Ceiling Finishes

Drywall rises to the second highest driver of emissions in Alberta because the Scenario 1 designs did not include the steel wall framing specified in Ontario. The lowest emitting drywall products available in both markets are similar, so the potential reduction of 4.6 tonnes is of similar scale.

3.3.3 Continuous Insulation Above Grade

The mineral wool board product specified in the Scenario 1 model is a relatively low emitting option. The bio-based products substituted in Scenarios 1 and 2 both have higher emissions, but offer 24 to 27 tonnes of carbon storage.

3.3.4 Framing

With no metal framing specified in the Scenario 1 models, framing drops to the fourth most intensive product category in the Alberta designs. The 3.9 tonne reduction in Scenario 2 comes from specifying wood products (framing and plywood) sourced from neighbouring British Columbia, where emissions for wood products are lower than the national average.

There is an impressive 63.7 tonnes of carbon storage in the framing category in Scenario 3. This arises from the substitution of compressed straw panels for the interior walls and structural sheathing for exterior walls, roof and floors made from elephant grass.

3.3.5 Windows

As with the Ontario models, there is no difference in the embodied emissions from windows across the three scenarios, due to a lack of product specific data that might point toward reduction opportunities.

3.3.6 Cavity Insulation

In Scenario 2, the average GWP of five different biogenic batt insulation products (sheep's wool, hemp wool, cellulose, wood fiber and grass) provides a modest 1.8 tonne emission reduction from Scenario 1 while adding 16.3 tonnes of storage. Each of these products feature feedstocks that are currently grown or available in Alberta and these products could be manufactured in the province. Currently, these products would need to be imported from the US or eastern Canada.

In Scenario 3, exterior wall cavity insulation is provided by hempcrete. This comes with an additional 8 tonnes of emissions but a substantial 15.3 tonnes of carbon storage. This product substitution was made because Alberta is currently home to the only commercial hempcrete manufacturer in the country, indicating this could be a feasible product in the province in the coming decade.

3.3.7 Cladding

As with the Ontario models, the Scenario 1 buildings use relatively low emitting engineered wood cladding, bringing this product category lower in the rankings than is typical in other studies.

Scenario 3 uses a biochar-based cladding product currently manufactured in Europe to add 27.6 tonnes of storage to the building. However, this product comes with a large GWP impact of 11.5 tonnes, responsible for the majority of the jump in emissions in this scenario. This points to the importance of encouraging the use of products that achieve carbon storage without incurring a substantial emission penalty. The European product uses biochar made from residue biomass that is abundant in Alberta and is a product that could feasibly be manufactured in the province.

3.4 Carbon Storage Potential

Both the Ontario and Alberta Scenario 1 designs do not feature any carbon storage in this analysis, as the carbon physically present in timber products are not attributed with storage that has inherently positive impacts on the climate.^{Footnote 32}

Table 3.4.1 shows the total amount of carbon storage in the Ontario and Alberta Scenario 2 and 3 models and the ratio of emissions to storage. In both provinces, the storage in Scenario 2 is at or near 50 percent of the total GWP, while Scenario 3 in both provinces far surpasses a 1:1 ratio with GWP. At a nationwide scale, carbon storage at this level could be one of the largest climate mitigation strategies available in the near term and achievable while providing Canadians with durable, healthy homes.

Table 3.4.1 Carbon Storage Potential Across All Designs

Carbon Storage Potential for All Designs
Ratios calculated from portfolio totals (all designs summed).

Province	Scenario	Emissions	Storage	Ratio
ON	Scenario 2	123.7	58.6	1:0.5
	Scenario 3	103.0	185.2	1:1.8
AB	Scenario 2	117.4	46.7	1:0.4
	Scenario 3	149.7	234.2	1:1.6

In Scenario 2, carbon storing products were selected based on commercial availability in the relevant province. Tables 3.4.2 and 3.4.3 highlight the products contributing the most carbon storage in each province.

Table 3.4.2 Carbon Storage Potential - Ontario - Scenario 2

Carbon Storage by Product - Ontario Scenario 2

Product Name	Storage (kgCO₂e)	Emissions (kgCO₂e)
Wood fiber board (Average)	-29,259	15,810
Cellulose batt (Ekovilla)	-21,383	16,918
Engineered wood siding (Average)	-5,504	906
Linoleum flooring (Tarkett)	-2,477	2,115
TOTAL	-58,624	35,749

In Ontario, wood fiber board used as continuous exterior insulation contributed the most storage. Currently there is a product manufactured in Quebec available through several retail building supply stores, and another product from Maine that recently began distribution in eastern Canada.

A version of the specified cellulose batt product used for cavity insulation is manufactured in Michigan and is available to order in Ontario, but is not available from retailers. Ontario is home to several manufacturers of cellulose insulation and this product could feasibly be made in the province or distributed through the retailers that currently stock loose fill cellulose products.

Engineered wood siding provided the third largest storage potential, though significantly smaller than the insulation products. The inclusion of timber products has not typically been counted as carbon storage with a known cooling effect on the climate, but has been included here to show the potential, especially for a product type that uses chipped/shredded feedstocks, should a definitive methodology for quantifying the storage impacts of timber products demonstrate a positive value.

A relatively small quantity of storage is evident in the linoleum flooring. There is currently no linoleum flooring production in Canada, but European products are widely available from retail flooring outlets.

Table 3.4.3 Carbon Storage Potential - Alberta - Scenario 2

Carbon Storage by Product - Alberta Scenario 2

Product Name	Storage (kgCO₂e)	Emissions (kgCO₂e)
Wood fiber board (Average)	-27,009	14,594
Bio-based batt (Average of sheep's wool, hemp wool, cellulose, wood fiber and grass)	-16,346	8,773
Cork plank flooring (Amorim Wise)	-2,080	839
Linoleum flooring (Tarkett)	-1,287	1,099
TOTAL	-46,721	25,305

The top two storing product types in Alberta Scenario 2 models are the same as Ontario, led by wood fiber board insulation. The cavity insulation products are different in Alberta, but still provide the second highest storage capacity. For this study, the average GWP and storage of five different bio-based batt insulation products was used. None are currently manufactured in Alberta, but are available through manufacturers in the western United States. All the products use feedstocks that are available from Alberta farms and could feasibly be produced in the province.

Cork and linoleum flooring have the third and fourth highest volumes of storage. Both product types are only manufactured in Europe but have substantial retail distribution in Alberta.

Scenario 3 features a wider variety of carbon storing products, most of which are not currently available through Canadian retail supply chains. Only products with substantial manufacturing capacity in other countries were included, providing evidence that manufacturing at a reasonable scale is possible in Canada. Tables 3.4.4 and 3.4.5 include the carbon storing products specified in each province in descending order of scale. Listed products account for 183,664 kg of the building's 185,253 kg total Scenario 3 storage; products without substantial manufacturing capacity elsewhere are not shown.

Table 3.4.4 Carbon Storage Potential - Ontario - Scenario 3

Carbon Storage by Product -Ontario Scenario 3

Product Name	Storage (kgCO₂e)	Emissions (kgCO₂e)
Blown straw insulation (Iso-Stroh)	-34,974	1,502
Ag residue board insulation (Hundred Year Materials, Preliminary LCA)	-31,200	3,350
Grass structural sheathing (Plantd, Preliminary LCA)	-29,160	5,017
Paper pulp composite sheathing panel (Honext)	-18,987	2,598
Bio-based cladding (Average of eelgrass, straw board & paper pulp board)	-15,672	9,060
Recycled cardboard (Wood Tube)	-12,225	1,342
Algae cement CMU (Prometheus Materials, Preliminary LCA)	-10,885	9,071
Cellulose batt (Ekovilla)	-9,498	7,514
Biochar concrete aggregate (Solid Carbon)	-8,777	741
Engineered wood siding (Average)	-5,559	1,032
Engineered wood flooring (Average)	-5,504	3,574
Fiber cement siding (Average)	-1,223	5,372
TOTAL of listed products	-183,664	50,173

The Ontario Scenario 3 models together store over 185 tonnes of CO2e. The top six products feature a combination of high storage and low GWP, with emission to storage ratios ranging from 1:1.75 to as high as 1:23.

Over 19 percent of the total storage comes from chopped straw cavity insulation, a product that is currently manufactured in Europe and could be manufactured in Ontario.

A board insulation product currently in development in Ontario, made from a mix of agricultural straw residues, accounts for 31 tonnes of storage. The preliminary LCA for the product points to very low GWP as well as high storage.

Rounding out the top three carbon storers is a structural sheathing panel made from a perennial grass feedstock. It is currently manufactured in the United States and has achieved full compliance with the International Building Code.

The fourth and fifth highest storers are both panel products used on interior walls and ceilings in place of drywall. The paper-pulp product offers exceptional fire performance and was modelled to replace Type X drywall. The average GWP and storage of three different products was modelled for interior surfaces that do not require fire performance (though two of the three offer high fire resistance). All four products are currently manufactured in Europe and the feedstocks for all of these products are available in Ontario.

The interior walls of the Ontario Scenario 3 models specified a product made from recycled cardboard to replace standard dimensional wood framing. This product is manufactured in Europe.

The foundations of the Ontario models use two carbon-storing products that have only recently come to market. The foundation walls are specified with concrete masonry units made from algae-based cement, currently produced in the United States and reaching close to a 1:1 storage-to-emissions ratio in a product category that has typically been a leading driver of emissions. The poured concrete elements (footings, slab, and CMU fill) are modelled with biochar aggregate replacement, also manufactured in the United States. Both products meet ASTM testing requirements for use in buildings, and both could be produced in Ontario using domestic feedstocks.

The Alberta Scenario 3 models have a higher total storage capacity, at over 234 tonnes of CO₂e.

In these models, some of the products offering substantial storage have low GWP values, but others have GWP values higher than the more conventional products they replace. Without a definitive way to compare the climate impacts of storage with GWP, it is uncertain what ratio of emissions to storage results in a positive climate outcome.

As with the Ontario models, chopped straw cavity insulation is the leading product for carbon storage, totaling over 45 tonnes.

Table 3.4.5 Carbon Storage Potential - Alberta Scenario 3

Carbon Storage by Product - Alberta Scenario 3

Product Name	Storage (kgCO₂e)	Emissions (kgCO₂e)
Blown straw insulation (Iso-Stroh)	-45,681	1,321
Compressed straw board panel (Durra)	-39,470	10,052
Biochar cladding (MadeOfAir)	-27,594	11,418
Straw insulation board (VestaEco)	-24,059	17,709
Paper pulp composite sheathing panel (Honext)	-21,530	2,947
Bio-based cladding (Average of eelgrass, straw board & paper pulp board)	-16,067	9,288
Hempcrete (Average)	-15,312	9,435
Grass structural sheathing (Plantd, Preliminary LCA)	-14,880	3,133
Biochar concrete aggregate (Solid Carbon)	-11,317	955
Straw structural sheathing board (VestaEco)	-9,345	6,875
Bio-based batt (Average of sheep's wool, hemp wool, cellulose, wood fiber and grass)	-3,465	1,860
Linoleum flooring (Tarkett)	-3,365	2,873
Bio-based interior panels (Average of straw board, paper sludge & eelgrass)	-1,614	933
Hemp Fiber Batt (Average)	-503	359
TOTAL	-234,200	79,157

The second largest source of storage is compressed straw board, specified to replace stud-framed interior partitions. Two additional straw-based panel products rank fourth and tenth. All three use compressed wheat straw, but at different densities and thicknesses depending on the application. The denser products use petrochemical binders and have higher emissions than the partition wall board, which relies on the lignin naturally present in the straw as a binder. These products were selected for the Alberta models because of the abundant volume of wheat straw available in the province.

A cladding product made from biochar and bio-resins is third on the list, and has the potential to be manufactured in Alberta.

Hempcrete (7th) and hemp fiber batt insulation (14th) use different parts of the industrial hemp plant. More hemp is grown in Alberta than any other province and has the potential to lead the country in hemp-based insulation products.^{Footnote 33}

The Scenario 3 models are not intended to pick winners from the growing set of bio-based building products on the market. It is impossible to tell which of these products will gain traction and become commercially competitive with incumbents. The selections here are intended to illustrate two things: the potential for carbon storage in new homes, and the diversity of feedstocks and product types already being manufactured abroad that could, with the right industry and government support, be manufactured in Canada.

3.5 Impact of Strategic Design Interventions

The material scenario analysis in Sections 3.1 and 3.2 focuses on direct product substitution: replacing one material with another while keeping design specifications largely constant. This section examines two additional strategies that require minor changes to the building plans.

3.5.1 Improved Energy Efficiency: Enhanced Insulation

A common assumption in building design is that improving thermal performance necessarily increases embodied carbon, because more insulation means more material and more material means more manufacturing emissions. The embodied carbon implications of enhanced insulation are only part of the picture: improved thermal performance also reduces operational emissions over the life of the building. But even on the embodied side alone, the reality is more nuanced than a simple more-equals-more equation.

Table 3.5.1 compares the embodied carbon outcomes of upgrading continuous insulation on exterior walls from R12 to R20 (a common energy performance improvement consistent with stricter NBC performance tiers) using three different insulation products: conventional mineral wool board (average emissions and lowest emissions in category), wood fiber board, and Agrispan agricultural fiber board, a newly developing Canadian product. (Emissions and storage for Agrispan are based on a preliminary EPD and should be treated as indicative until a verified EPD is available.)

Results in Table 3.5.1 are also shown as emissions and storage intensity per square metre of area, enabling comparison in other building models with different wall areas to be insulated.

Table 3.5.1 Emissions Impact of Energy Performance Improvement via Insulation Increase

Continuous Insulation Upgrade on Walls ON Fourplex, 334 m² wall area

Scenario	Product	Insulation Level	Emissions (kgCO₂e)	Emissions per m² (kgCO₂e/m²)	Storage (kgCO₂e)	Storage per m² (kgCO₂e/m²)
Scenario 1	Mineral wool board, light density, (NAIMA average)	R12	1,892	5.66	0	0
		R20	3,153	9.44	0	0
Scenario 1	Mineral wool board (Best in category)	R12	1,482	4.44	0	0
		R20	2,471	7.40	0	0
Scenario 2	Wood fiber board (Gutex Multitherm)	R12	2,189	6.55	6,196	19
		R20	3,649	10.93	10,327	31
Scenario 3	Ag residue board (Agrispan)	R12	719	2.15	6,695	20
		R20	1,202	3.60	11,200	34

As expected, adding insulation adds emissions. Upgrading continuous insulation from R12 to R20 raises the gross embodied emissions of the insulation layer by about 67 percent for any given product, because the increase tracks the additional material used. Product selection cannot change that rate, but it changes what the upgrade costs in carbon. With the category-average mineral wool board, the upgrade adds 3.8 kg CO₂e/m². Making the switch to the lowest-emission board at the same time as the thickness upgrade adds only 1.7 kg CO₂e/m², less than half as much, because the better product offsets most of the added material. More insulation still means more embodied emissions. Product selection determines how much more.

In Scenario 2, the wood fiber board shows the same proportional increase of about 67 percent when moving from R12 to R20. Its gross emissions at R20, 10.9 kg CO₂e/m², are roughly 16 percent higher than the average mineral wool board.

However, a significant amount of carbon storage comes into play and for this product the ratio of emissions to storage is an impressive 1:2.8, providing 19 kg CO₂e/m² of storage at R12 and 31 kg CO₂e/m² at R20. As noted in Section 2.8, there is a substantial climate benefit to using products with emissions to storage ratios higher than 1:1, and while it is currently difficult to directly compare emissions and storage, the quantity of storage in this example is likely to result in better climate outcomes for the building.

Scenario 3 provides the best case, in which the emissions from the product at R20 are actually 36 percent lower than the category-average Scenario 1 product at R12. In this example, a significant improvement in thermal performance (which will lead to a reduction in operating emissions for the building) is combined with a significant reduction in embodied emissions as well as providing an emissions to storage ratio of 1:9.3.

This exploration breaks the oversimplified notion that improving thermal performance must come at the cost of higher embodied emissions. Within a single product, emissions do rise in proportion to the material added. Across products the picture changes entirely: at minimum, product selection more than halves the carbon cost of the upgrade, and at best a low-carbon product delivers the higher thermal performance at substantially lower emissions than the thinner conventional assembly it replaces. Designers and builders should not consider the use of more insulation as inherently negative for embodied emissions, but should explore ways in which product selection is able to support both improved thermal performance and reduced embodied emissions. If this approach can be accompanied by a high ratio of carbon storage, it’s possible to achieve a rare win-win-win scenario.

3.5.2 Using Less: Design Interventions Beyond Product Swapping

The product substitutions explored in this study all work the same way: swap one product for another one with lower emissions. The results in Sections 3.1 and 3.2 demonstrate the extent of embodied carbon performance such strategies can deliver. But there is a second strategy for reducing embodied carbon that does not depend on what products are specified at all: using less material. Design interventions that reduce the quantity of any product in the building provide proportional embodied emissions reductions, and they typically lower costs at the same time because less product often results in lower costs.

Because this study uses designs from the Housing Design Catalogue, no attempt has been made to alter the overall designs. A comprehensive design review focused on material efficiency can often result in substantial reductions, but such a review falls outside the scope of this analysis.^{Footnote 34}

The foundation is among the highest embodied carbon assemblies in these designs, driven primarily by concrete and reinforcing steel. Three interventions were modelled on the Ontario Fourplex 01 model to illustrate the potential to reduce concrete use and have a positive impact on embodied carbon.

Table 3.5.2 Carbon Impact of Reduced Slab Thickness via Design Intervention

Emission Reductions from Design Interventions ON Fourplex, 120 m² slab floor area

Design Intervention	Scenario 1 (kgCO₂e)	Alternative (kgCO₂e)	Total Reduction (kgCO₂e)	Reduction (%)	Reduction per m² (kgCO₂e/m²)
Reduced slab thickness, same mix (25 MPa, 20% FA)	4,108	2,739	1,369	33%	11.4
Reduced slab thickness + low carbon concrete (25 MPa, 50% FA)	4,108	2,055	2,053	50%	17.1
Painted slab (engineered wood and tile flooring replaced with concrete stain)	860	82	778	90%	6.5
Reduced slab thickness + low carbon concrete + painted slab	4,968	2,137	2,831	57%	23.6
“Slabless slab” Concrete slab replaced by double layer of plywood	4,108	1,003	3,105	76%	25.9

3.5.2.1 Reduced slab thickness

The energy model for the Scenario 1 fourplex design specifies a standard 6-inch concrete slab (25 MPa, 25% fly ash) over 120 m² of floor area. The NBC 2020 states that "Floors-on-ground (slabs) shall be not less than 100 mm (4 in.) thick, except where other conditions (like garage slabs or structural requirements) may necessitate more robust design,"^{Footnote 35}, a minimum thickness that is also permitted by the International Residential Code^{Footnote 36}. A 4-inch slab is therefore feasible under both Canadian and US residential codes.

The slab thickness reduction is an example of the linear relationship between embodied emissions and product quantity, with both concrete volume and emissions reduced by 33 percent. This represents a reduction of 11.4 kg CO₂e/m², and this reduction can be applied to any design where slab thickness is reduced by the same amount.

3.5.2.2 Reduced slab thickness + low carbon concrete

It is possible to combine the “use less” and “use better” strategies, pairing a thinner slab with a concrete mix that has lower emissions, stacking the benefits of both to result in a 50 percent reduction or 17.1 kg CO₂e/m².

3.5.2.3 Use less flooring material

Ontario Scenarios 1 and 2 substituted a concrete stain product for the engineered wood and tile flooring specified in the Scenario 1 design, providing another variation of the “use less” strategy. In this case, a 90 percent reduction in emissions is achieved.

3.5.2.4 Reduced slab thickness + low carbon concrete + painted slab

By combining all three interventions, the embodied emissions for the Ontario Fourplex 01 was reduced by an impressive 57 percent or 23.6 kg CO₂e/m². The entire Scenario 1 building has an embodied emissions of 53,980 kg CO2e, meaning that these three interventions alone will drop the emissions of the whole building by 5 percent.

Using less typically costs less, making this a good strategy for reducing emissions and costs together. The thinner slab will result in material cost reductions of approximately 33 percent and moving from low-cost engineered wood and tile flooring to a concrete stain finish reduces material costs by approximately $22/m² or $2,640 for the Ontario Fourplex 01.^{Footnote 37}

3.5.2.5 The “slabless slab”

Fine Homebuilding and JLC have documented and promoted concrete-free plywood slab systems for several years, driven by lower cost, faster construction, better thermal performance at slab edges, and easier repairability.^{Footnote 38Footnote 39}. There are also significant embodied emission reductions available from this strategy. Replacing the concrete slab with a double layer of 3/4-inch plywood deck reduces the overall volume of material and substitutes a lower emitting product.

For the Ontario Fourplex 01, the slabless slab reduces emissions by 76 percent or 25.9 kg CO2e/m², a savings on emissions of 6 percent for the Ontario Fourplex 01 design.

3.6 Cost Comparison Findings

Affordability is a leading concern in the current Canadian housing market, which leads to a critical question: How much does it cost to achieve carbon emission reductions and carbon storage increases? It is unlikely that builders and homeowners will choose to increase the cost of a home in order to reduce its climate impact. An exploration of the cost impacts of the leading emission reduction strategies finds that cost implications vary on a product by product basis, but that many of the most substantial reductions do not come with a cost premium.

To ascertain costs, the Ontario and Alberta fourplex designs were examined to determine the product substitutions from the Scenario 1 to Scenario 2 that provide the largest overall reductions in emissions and gains in storage. For each product substitution, pricing was determined by searching the websites of a major building supply retailer or, when products were not available from the retail outlet, the price was found on the website of the nearest distributor for the product. Only material costs were counted, as labour/installation costs were assumed to be neutral because each product substitution was selected to have similar installation methods and should not change the construction process or required trades in a substantial way. Pricing for building materials can be volatile, fluctuating with raw material availability, currency exchange rates, tariffs, and other factors; the figures presented here reflect a March 2026 snapshot, and current pricing is required to confirm any specific cost-reduction scenario.

Table 3.6.1 Cost Implications of Low Carbon Product Substitutions - Ontario

Ontario: Cost implications of low carbon product substitutions

Product Category	Scenario 1 Product	Scenario 2 Product	Emissions Reduction (kg CO2e)	Cost Impact ($)	Cost Category
Concrete	Concrete – 25 MPa, 15% SL, GU, Ontario	Concrete – 25 MPa, 50% SL, GUL, Ontario	2,625	$0.00	No cost
Cladding & Roofing	Metal Panels – Steel, Canadian Average	Metal panels – Steel, lowest emission in category	2,013	$0.00	No cost
Drywall	1/2 and 5/8 inch drywall, average in category	1/2 and 5/8 inch drywall, lowest emissions in category	1,898	$0.00	No cost
Wall framing	Steel studs, 600-S-137-54, 16 gauge	Wood studs, SPF, 2x6	5,203	-$3,528	Savings
Continuous insulation (Below Grade)	XPS foam board, R5.0/inch	Mineral wool board, light density, R3.9/inch	660	-$542	Savings
Sub slab insulation	XPS foam board, R5.0/inch	EPS foam board with graphite, R 5.0-inch, Type IX	532	-$930	Savings
Exterior sheathing	Gypsum panels – glass mat, 5/8" Type X, average	Gypsum panels – glass mat, 5/8" Lowest emissions in category	495	-$685	Savings
Foundation wall barrier	Ext. Waterproofing Barrier, adhesive, highest emissions	Ext. Waterproofing Barrier, adhesive, lowest emission in category	446	-$3,291	Savings
Slab floor finish	Engineered Wood & Ceramic tile average	Water-Based Concrete Stain	374	-$3,846	Savings
Total emissions and cost impact for all substitutions			14,246	-$12,822

Note: values are the change in gross A1–A3 emissions from Scenario 1 to Scenario 2. This table covers the substitutions that reduce gross emissions; biogenic carbon storage is reported separately in Section 3.4, and the whole-building reduction for this design is given in Table 3.1.2.

Table 3.6.1 shows nine product substitutions priced for the Ontario Fourplex 01, every one of which reduces embodied emissions. Together they avoid 14.2 tonnes of carbon, 26 percent of the design's Scenario 1 total of 54.0 tonnes. Six of the nine also reduce material cost and the other three are cost-neutral, so adopting all nine saves approximately $12,800.

The two remaining priced substitutions, a cellulose batt cavity insulation and a wood fibre board continuous insulation, are not shown in Table 3.6.1. Both raise gross emissions slightly and are specified in Scenario 2 for their carbon storage rather than for emissions reduction, so they fall outside the question this table asks. Including them, the full set of eleven priced substitutions reduces gross emissions by 12.2 tonnes, 23 percent of the Scenario 1 total, and still returns a net saving of approximately $3,600. Their biogenic storage is reported in Section 3.4.

The largest single reduction comes from wall framing, which cuts 5.2 tonnes while saving $3,528. Across the bundle the saving works out to $35/m² of project floor area. This substitution applies only where building codes and site conditions permit combustible construction; see Section 3.2.2. Low carbon concrete, drywall and steel roofing and cladding had major emissions reductions with neutral cost implications. Changes to the foundation waterproofing barrier and substituting the mix of engineered hardwood and ceramic tile flooring for a painted slab finish saved a total of $7,137, but only reduced emissions by 0.8 tonnes. The painted slab finish also likely saves on labour costs and installation time, making it the only substitution in this list that is not a straightforward product swap. Clearly, there are win-win opportunities for builders who can use embodied emission data to identify product procurement decisions that reduce emissions and cost together.

The pattern is similar in the Alberta example, though some of the product substitutions and their costs are different than in Ontario.

Table 3.6.2 Cost Implications of Low Carbon Product Solutions - Alberta

Alberta: Cost implications of low-carbon product substitutions

Product Category	Scenario 1 Product	Scenario 2 Product	Emissions Reduction (kg CO2e)	Cost Impact ($)	Cost Category
Concrete	Concrete – 25 MPa, 10% FA, GU, Concrete Alberta	Concrete – 25 MPa, 20% FA, GUL, Concrete Alberta	2,883	$0.00	No cost
Drywall	1/2 and 5/8 inch drywall, average	1/2 and 5/8 inch drywall, lowest emissions in category	1,775	$0.00	No cost
Roofing	Metal Panels – Steel, Canadian average	Metal panels – Steel, lowest emission in category	1,221	$0.00	No cost
Structural sheathing	Plywood, ⅝ inch, Canadian average	Plywood, ⅝ inch, British Columbia average	1,211	$0.00	No cost
Laminated strand lumber (LSL) / AWC & CWC	LSL, Canadian average	Laminated strand lumber (LSL), lowest emission in category	358	$0.00	No cost
Sub slab & continuous insulation	XPS foam board, R5.0/inch	EPS foam board with graphite	1,214	-$5,938	Savings
Liquid applied membrane	Ext. Waterproofing Barrier, liquid applied, highest emissions	Ext. Wall barrier, liquid applied, lowest emissions in category	421	-$1,554	Savings
Flooring	Engineered Wood Flooring, 3/8"–3/4", Canadian average	Amorim Wise Cork plank flooring 4 mm	1,523	$11,159	Increase
Cavity insulation	Fiberglass batt, Canadian average	Average for bio-based batt products, incl. sheep's wool, hemp wool, cellulose, wood fiber and grass	522	$10,361	Increase
Total emissions and cost impact for all substitutions			11,128	+$14,028

Note: values are the change in gross A1–A3 emissions from Scenario 1 to Scenario 2. Biogenic carbon storage is reported separately in Section 3.4, and the whole-building reduction for this design is given in Table 3.1.2.

Table 3.6.2 shows nine product substitutions priced for the Alberta Fourplex 02, every one of which reduces embodied emissions. Together they avoid 11.1 tonnes of carbon, 18 percent of the design's Scenario 1 total of 60.3 tonnes. The full Scenario 2 material palette, including substitutions that were not priced, reduces the building's embodied carbon by 22 percent relative to baseline (Table 3.1.2); the substitutions priced here are the cost-relevant subset. Of the nine, five were cost neutral and two reduced cost, while two bio-based products, cork flooring and bio-based cavity insulation, carry a premium. Adopting all nine results in a net material cost of $14,028.

The biggest reduction in embodied emissions comes from product substitutions that are cost neutral. These changes result in over 7.4 tonnes. An additional 1.6 tonnes of emissions can be avoided while saving $7,492. Together, these measures can avoid 15 percent of the building’s total emissions while providing meaningful cost savings of $17/m² of project floor area.

Procuring low carbon concrete provides the single biggest emission reduction of 2.8 tonnes with no cost premium. A switch from XPS to EPS foam board for continuous and sub slab insulation provided the biggest cost savings of $5,938 with moderate emissions reductions of 1.2 tonnes.

Two product substitutions resulted in higher costs: the bio-based batt cavity insulation saved 0.5 tonnes of emissions at a price tag of $10,361, and the cork flooring reduced 1.5 tonnes for $11,159.

3.6.1 Identifying affordable emission reductions

These results should not be considered prescriptions for finding affordable reductions in embodied emissions. The product substitutions selected in this study do not represent the full suite of potential alternatives, and different selections would change both the emissions and cost results.

Instead, these results should provide evidence that embodied emissions reductions do not necessarily come with higher costs. In fact, more of the substitutions in this study come with either cost reductions or neutral costs.

Delivering new homes affordably is a complex task, requiring designers and builders to balance a range of factors to arrive at a finished product that is desirable for home owners and performs to expectations while meeting the desired sales price. These results indicate that, with proper access to embodied emission data for products, low-carbon can become one of the many factors being weighed and that, in many cases, the low-carbon product does not carry a cost liability.

Product substitution decisions require thorough research and should not be based on embodied emission factors alone. In each product category a builder must be careful to ensure that the performance characteristics of substituted products meet code requirements and durability intentions as well as price factors. Design details may need to be changed to accommodate product substitutions for differences such as product thickness or installation requirements. As demonstrated in this study, product substitutions can have very different cost outcomes that must be considered.

3.7 Whole-Building Emissions Performance

Upfront embodied emissions represent a substantial release of GHGs that occur prior to the occupation and operation of a building. As such, they are emissions that enter the atmosphere early in the life cycle of a building and cannot be withdrawn or altered and they will continue to increase warming year after year and decade after decade.

Once a building is occupied, emissions associated with operating the building begin to accumulate over time. These emissions will grow as a percentage of the building’s total emission profile and will typically come to dominate the building’s total emissions within a couple of decades. However, unlike embodied emissions, it is possible to bend the accumulation curve for operational emissions in two ways: improve the thermal performance of the building (with increased air tightness, more efficient mechanical equipment or improved thermal performance from windows and/or insulation) and/or providing the building with energy produced with lower emissions. Electrification of buildings, using heat pumps rather than gas furnaces, is a leading strategy for reducing operational emissions, and efforts to provide cleaner energy sources to the electrical grid serving a building is a priority for utility companies across Canada.

The model buildings included in the Housing Design Catalogue each have an associated energy model that provides operational emissions information. These energy models use fossil gas furnaces as the primary heating scenario, which represents the high end of operational emissions. The Catalogue provides alternate mechanical systems in both provinces for this reason: a cold-climate air-source heat pump (ccASHP) with supplementary gas in Alberta, and various hybrid and all-electric options in Ontario. Modelled as an all-electric building with a heat pump, the operational emissions would be reduced.

A more complete emissions profile emerges when embodied emissions are combined with cumulative operational emissions. For the Ontario Fourplex 01, this analysis uses a 25-year time horizon. The horizon is shorter than the expected lifespan of the building, but it captures one full replacement cycle for mechanical equipment, while most of the structural and envelope products modelled remain in place over that period. Modelling a longer life cycle would require additional assumptions about replacement products, equipment, and grid emissions factors.

Figure 3.7.1 Embodied Emissions Plus Cumulative Operational Emissions

Text version

Stacked column chart on the left depicting the embodied emissions, as well as a cumulative emissions pathway / stacked waterfall chart on the right. The x-axis has two components: it includes the three scenarios labelled from left to right under the stacked column chart, and a 25-year horizon with each year identified ascending from left to right. At year 25, the difference in the total emissions profile of each building is the difference in their embodied emissions: 129 t for Scenario 1, 116 t for Scenario 2 and 109 t for Scenario 3.

The Ontario Fourplex 01 Scenario 1 model has 54 tonnes of embodied emissions and adds 3 tonnes per year of operational emissions. At that operational rate, it takes 18 years for a building's cumulative operational emissions to equal its embodied emissions. This has direct implications for 2035 climate targets: for any building completed in the years ahead, embodied emissions will be the larger share of lifetime emissions when those targets come due. Both need to be addressed, but embodied carbon is the more urgent lever.

The Scenario 2 model reduces embodied emissions by 24 percent, to 41 tonnes. At the same operational rate, operational emissions equal embodied emissions after 14 years, by 2040. Additionally, the Scenario 2 model is responsible for 17 tonnes of carbon storage, which will have a cooling effect on the climate that provides some degree of counterbalancing the warming effects caused by emissions.

The Scenario 3 model improves further, with reduced emissions and increased storage. Operational emissions begin to dominate at year 11.

At year 25, the difference in the total emissions profile of each building is the difference in their embodied emissions: 129 t for Scenario 1, 116 t for Scenario 2 and 109 t for Scenario 3. Unless the operational performance of the building is improved in the first 25 years, the only way to improve the overall outcome is to address embodied emissions.

Looking at a building’s emissions in a holistic manner such as this can provide important insights for decarbonization efforts. In the case of the Scenario 2 building, the 25 year outlook suggests that efforts to reduce operational emissions may be more impactful over the long term. Were this building to be fully electrified and operating on an electrical grid with relatively low emissions intensity, the embodied emissions would dominate the profile and would provide the most impactful reductions.

4. CONCLUSIONS

The central finding of this study is straightforward: the embodied emissions of the materials used to build a home determine a significant portion of its lifetime climate impact, and there are immediate and substantial reductions available by substituting commercially available and affordable lower-emission products.

Canada does not have to resolve the tension between building more homes and building lower-carbon homes, because for the most part, that tension can be resolved through design and procurement decisions made by professionals with access to good embodied emission data.

The results of this study point to several broad conclusions that are relevant for designers, builders, and policy-makers. These conclusions highlight where the most immediate opportunities lie, as well as the conditions needed to scale embodied carbon reductions across the housing sector.

1. Embodied emissions outweigh operational emissions through a new home's first 18 years.
   For its first 18 years, the Ontario fourplex modelled here emits more carbon in its materials than in its operation, and under the all-electric heating option the Catalogue already provides, that period extends to 49 years. Electrification avoids more carbon over 25 years than the material change does, but operational emissions can be bent downward later and embodied emissions cannot. This asymmetry, not the size of the reduction, is what makes material selection the more urgent decision.
2. Commercially available product substitutions enable immediate reductions.
   Scenario 2 achieved average embodied emission reductions of ~23 percent (range 14–26 percent) across all designs using products that are already available and compatible with current construction practices.
3. Embodied emission reductions do not require higher costs.
   Cost analysis of the Ontario and Alberta fourplexes shows that many of the largest reductions are cost-neutral or cost-saving, indicating that lower-emission product choices can align with affordability objectives.
4. A small number of products drive a high percentage of emissions.
   Concrete, framing, insulation, and interior finishes account for a disproportionate share of embodied carbon, providing a clear and practical focus for reduction strategies.
5. Energy performance upgrades need not carry a large embodied carbon penalty. Increasing continuous insulation from R12 to R20 raises the insulation layer's emissions by about 67 percent for any product, but selecting a lower-emission board at the same time more than halves the carbon cost of the upgrade. This matters as energy codes move toward higher thermal performance.
6. Carbon storage represents a significant emerging opportunity.
   Scenario 3 demonstrates that bio-based materials can substantially increase carbon storage, in some cases exceeding total embodied emissions, highlighting the importance of supporting these product pathways.
7. Results are regionally variable but broadly consistent.
   Differences in product availability and cost between Ontario and Alberta affect specific outcomes, but the overall strategy – better product selection and increased use of bio-based materials – applies across regions.
8. Further gains require material efficiency and better data.
   Combining product substitution with “use less” design strategies can unlock additional reductions, while improved EPD coverage and standardized methods are needed to support consistent decision-making.

The Housing Design Catalogue already exists. The six designs studied here are real, code-compliant, architect-designed plans, ready to build across the country. What this study adds is a demonstration that these designs can be built with low carbon materials to deliver substantially lower embodied carbon with no additional cost or performance penalties. The Catalogue leaves material selection to the builder, and the Materials Guide already points toward lower-embodied-carbon options. Building upon the findings of this study and the Catalogue resources to develop more targeted low-carbon product sourcing guidance would give designers and builders a clear basis for weighing lower impact options, without requiring new regulation, new technology, or new training. This can also help expand policy commitments to include embodied emissions as a standard design consideration alongside energy performance, accessibility, and cost. The data infrastructure to do that is already in place in the form of tools like BEAM and Material Carbon Emissions Estimator (MCE2).

Four recommendations follow from these findings:

1. Build upon the evidence to provide more targeted low-carbon product sourcing guidance for designers and builders leveraging the findings of this study and existing Catalogue resources. This would put the carbon and cost evidence for Scenario 2 products into designers and builders' hands at the point where material decisions are made, so lower-carbon options can be weighed on the same footing as cost and performance.
2. Embodied emissions should be integrated into housing program requirements alongside energy performance targets. The Catalogue's existing NBC 2020 Tier 3 energy baseline demonstrates that performance standards can be embedded in pre-designed housing solutions. The same model applies to embodied emissions. The Canadian National Model Code is set to address embodied carbon in 2030. That is a clear target and a fixed deadline. The Catalogue is a platform that can get builders there without starting from scratch.
3. Investment in domestic biomaterial supply chains should be treated as housing policy as much as climate policy, because the two are intertwined. EPD development, domestic manufacturing capacity, and approval pathways for emerging products are not niche environmental priorities but prerequisites for the potential demonstrated in Scenario 3 examples, and the feedstocks to support them already exist across the country.
4. Frameworks to recognize and value biogenic carbon storage in building standards, procurement policy, and lifecycle assessment practice would significantly strengthen the market case for bio-based materials. The storage potential demonstrated in this study currently has no mechanism for recognition in Canadian building codes or carbon pricing frameworks. Ongoing work in dynamic lifecycle assessment methodology is an important step toward resolving the methodological questions that underpin this recognition. Translating that progress into policy and procurement signals would make the Scenario 3 potential visible to the market, not just to researchers.

Canada has the feedstocks. It has the data. The evidence assembled in this study points in one direction: the cost of acting is low, the tools are in hand, and the housing crisis makes delay increasingly difficult to justify on any grounds. Building more and building better are not competing priorities. They are the same priority, and the path to both runs through the material specifications of the homes being built right now.

GLOSSARY

ADU (Accessory Dwelling Unit)

A self-contained residential unit on the same property as a primary dwelling. ADUs can be attached to or detached from the main home, or converted from existing space such as a basement or garage. They represent a form of gentle density, adding housing units to existing neighbourhoods without changing the built form or scale of the street.

Biogenic carbon

Carbon that originates from living or recently living organic material, including plants, agricultural residues, and wood products. When bio-based materials are used in construction, the carbon absorbed by those plants during growth is physically stored in the building. This study reports biogenic carbon storage as a separate metric from gross emissions, because the two involve different units and different timeframes that cannot be directly compared without methodological assumptions that dynamic LCA research is still working to resolve.

dLCA (Dynamic Lifecycle Assessment)

An emerging methodology for evaluating the climate impact of buildings over time, accounting for the fact that carbon stored in bio-based materials and carbon emitted through manufacturing occur at different points in time and have different warming effects depending on when they happen. Unlike conventional LCA, which treats all emissions and storage as equivalent regardless of timing, dynamic LCA assigns greater weight to near-term emissions and discounts future sequestration. NRCan is among the institutions developing approaches for the Canadian context.

Embodied carbon

The greenhouse gas emissions associated with the manufacture, transport, installation, maintenance, and end-of-life disposal of building materials. Unlike operational carbon, which is produced during a building's use, embodied carbon is largely locked in at the time of construction. This study focuses on cradle-to-gate embodied carbon, covering lifecycle stages A1 to A3: raw material extraction, processing, and transport to site.

EPD (Environmental Product Declaration)

A standardized, third-party-verified document that reports the environmental impacts of a specific product across its life cycle, based on a common set of rules for a given product category. EPDs are the primary data source for embodied carbon calculations in this study and in most contemporary lifecycle assessment tools, including BEAM. Where no EPD exists for a product, peer-reviewed lifecycle assessment studies are used instead.

Gentle density

An approach to increasing housing supply that adds units to existing residential neighbourhoods without dramatically altering their scale or character. Gentle density typically refers to ADUs, duplexes, triplexes, fourplexes, and other small multi-unit formats that fit within the footprint and massing of single-family areas. It is distinguished from high-density redevelopment by its incremental nature and its compatibility with existing neighbourhood infrastructure.

GWP100 (Global Warming Potential at 100 years)

A standardized measure of how much warming a greenhouse gas causes over a 100-year period, expressed relative to CO₂. GWP100 is the basis for reporting embodied carbon in this study and in most building lifecycle assessment tools, including BEAM. Biogenic carbon storage is physically removed from the atmosphere at the time of construction, while GWP100 measures warming impact over a future century, which is why the two metrics are not directly subtracted in this study.

Missing middle housing

A term describing residential building types that sit between detached single-family homes and large apartment towers, including duplexes, triplexes, fourplexes, townhouses, and small apartment buildings. Missing middle housing is considered "missing" because zoning regulations in many Canadian cities have historically restricted or prohibited these forms in residential neighbourhoods, limiting housing supply and affordability.

SCMs (Supplementary Cementitious Materials)

Materials added to a concrete mix to replace a portion of Portland cement, which is the leading contributor to concrete emissions. Common SCMs include fly ash (a by-product of coal combustion), ground granulated blast-furnace slag (a by-product of steel manufacturing), and silica fume. Increasing the proportion of SCMs in a concrete mix lowers its embodied carbon without changing the mix's structural performance for most residential applications.

Appendix A: Builder and Policy Briefs

A Builder's Guide to Affordable Embodied Emission Reductions

Practical substitutions to cut emissions without raising costs

This study modelled six designs from the Housing Design Catalogue using commercially available low-carbon material substitutions. The average reduction in embodied carbon was 23%, achieved entirely through product swaps that require no change to design, labour, or construction sequence. This guide distills those findings into a practical reference for builders looking to reduce the carbon footprint of their projects without compromising schedule, quality, or cost.

Priority substitutions: low-risk, high-impact changes

The substitutions below deliver the largest emissions reductions with the least disruption to standard practice. Each one uses products available through established Canadian supply chains and requires no change to the design, labour, or installation methods the building already calls for. They are ranked by combined emissions and cost impact on the Ontario Fourplex 01 design (similar patterns apply to the Alberta fourplex and to larger typologies).

What to substitute	Current Scenario 1	Lower-carbon option	CO₂e saved	Cost impact
Wall framing (where steel studs are specified)	Steel studs, 16 gauge	Wood studs, SPF 2x6	-5,203 kg	Saves $3,528
Concrete mix (all pours)	25 MPa, 15% slag	25 MPa, 50% slag, GUL cement	-2,625 kg	No change
Metal cladding and roofing	Standard Canadian-average steel	Lowest-emission steel in category	-2,013 kg	No change
Drywall	Category average	Lowest-emission product in category	-1,898 kg	No change
Continuous exterior insulation	XPS foam board	Mineral wool board (light density)	-660 kg	Saves $542
Sub-slab insulation	XPS foam board	EPS foam board with graphite	-532 kg	Saves $930
Slab floor finish	Engineered wood + ceramic tile	Water-based concrete stain	-374 kg	Saves $3,846

Figures are from the Ontario Fourplex 01 cost analysis (Table 3.6.1 of the main report). Every substitution above was modelled against the Catalogue designs and produces either cost savings or no change in material cost. The combined effect of all seven substitutions on the Ontario Fourplex 01: -13.3 tonnes CO₂e, saving approximately $8,800 in material costs.

Sourcing low-emission materials in Canada

Most of the substitutions above rely on products already available through Canadian retail and distribution channels. Some require a call to a regional distributor rather than retailer sourcing. None require importing from outside North America. The table below summarizes where the key products are manufactured or distributed today.

Product category	Where it is made or distributed	What to ask your supplier for
Low-carbon concrete	Ready-mix plants across Ontario; availability in Alberta is expanding but varies by region	Portland limestone cement (GUL) with 50% slag or fly ash replacement; request the mix's EPD
Wood fiber board insulation	Manufactured in Quebec; additional product recently available from Maine with eastern Canada distribution	Wood fiber board (continuous exterior insulation, R-3.9 to R-4 per inch)
Cellulose batt insulation	Manufactured in the northeastern US with Ontario distribution; loose-fill cellulose is widely made in Canada	Cellulose batt (for fiberglass batt replacement); or blown-in cellulose where batts are not required
Bio-based cavity insulation (Alberta)	Sheep's wool, hemp wool, wood fiber, and grass batts available from US manufacturers	Any bio-based batt; Alberta feedstocks support future domestic production
Low-carbon steel (cladding, roofing)	Available from major Canadian steel suppliers	EPD-verified lowest-emission product in each supplier's catalogue
EPS foam board with graphite	Widely available across Canadian building supply retailers	Type II or IX graphite-enhanced EPS depending on application

Product availability and pricing changes frequently. When in doubt, ask suppliers for an EPD (Environmental Product Declaration); a verified EPD is the most reliable signal that a product's embodied carbon has been independently measured.

Building science for bio-based materials

Bio-based materials behave differently from the synthetic products they replace, but the adjustments are typically minor. Three practices handle most of what is different. First, manage moisture actively. Bio-based insulations are more vapour-open than closed-cell foams, which is an advantage for drying potential, but makes air and vapour control layer placement more important. Second, respect drying time. Cellulose and wood fiber products should be installed into assemblies that can dry, and protected from bulk water during construction. Third, detail for durability. These products perform well for the life of the building when installed in assemblies that keep them dry and allow modest seasonal moisture cycling. This is the same building science that applies to any moisture-managed wall, applied with slightly more attention.

Housing Supply and Embodied Emissions: A Policy Brief

How federal policy can align Canada's housing and climate objectives through material specification

Canada's housing and climate agendas have often been framed as competing priorities. The scale of construction required to restore affordability — up to 480,000 new units per year by 2035 — carries an embodied carbon burden that Canada's climate commitments simply cannot absorb. This study demonstrates that the trade-off is not inevitable.

Using the Housing Design Catalogue, this study modelled six representative designs across three material scenarios. Commercially available low-carbon product substitutions reduced embodied emissions by an average of 23% across all six designs, at little or no additional cost. In the Ontario fourplex the substitutions that reduce emissions produced a net saving of approximately $12,800, or $3,600 with the two products specified for carbon storage included; in the Alberta fourplex most substitutions were cost-neutral or cheaper, with a net cost of approximately $14,000 concentrated in two bio-based products whose supply chains are still developing. The substitutions required no substantial changes to design, construction method, or labour. For the first 18 years of a building's life its embodied emissions exceed everything it has emitted in operation, and under all-electric heating that period extends to 49 years. With emerging bio-based materials, every design stored more carbon than was emitted to build it. The levers to resolve the housing-climate tension already exist at the material specification level. What is missing is the policy direction.

Four policy levers, four instruments

The table below maps the four policy areas to existing federal instruments where embodied carbon direction could be set or strengthened. These are existing vehicles where embodied carbon can be incorporated.

Policy lever	Instruments and opportunities
Embodied carbon benchmarks and targets	2030 National Model Codes (embodied GHG provisions in development through CBHCC Phase 1 policy positions); municipal pilots (City of Vancouver Building By-Law embodied carbon requirements, Toronto Green Standard); federal disclosure measures under the Canada Green Buildings Strategy
Incentive mechanisms	Housing Accelerator Fund action plans (currently prioritize low-carbon communities but do not require embodied carbon metrics — a gap worth closing); Canada Housing Infrastructure Fund (conditions tied to National Building Code adoption); CMHC Eco Plus and Eco Improvement mortgage insurance rebates (currently tied to operational energy performance — could be extended to embodied carbon)
Procurement policy	Greening Government Strategy "buy clean" approach; Buy Canadian policy; Build Canada Homes (federal affordable housing procurement at scale)
Domestic bio-based supply chains	This is where the policy gap is largest. No existing federal instrument directly supports domestic bio-based building material manufacturing capacity. The Strategic Response Fund (successor to the Net Zero Accelerator) and the Clean Technology Manufacturing ITC could be adapted to cover this category, but neither currently does.

Four recommendations for federal policy

1. Set embodied emissions benchmarks for federally-supported housing

The National Model Code is expected to address embodied emissions in the 2030 code cycle. Federal housing programs should not wait for code adoption to set direction. This study's findings show that a 20% reduction in embodied carbon is achievable today using commercially available products, with the bulk of that reduction available at no additional cost. The remaining share, tied to bio-based insulation and flooring, carries a modest premium that is expected to narrow as Canadian supply chains mature. Setting an interim benchmark at this level for federally-supported housing, whether through the Canada Green Buildings Strategy, the Housing Accelerator Fund, or Build Canada Homes, would create consistent market signals for builders and manufacturers and position Canada ahead of the 2030 code transition rather than behind it.

2. Close the incentive gap for low-emission building materials

Canada has no federal incentive program specifically designed to accelerate the use of low-carbon materials in new construction. Existing programs target operational energy (Canada Greener Homes, Codes Acceleration Fund) or retrofits (Greener Homes Affordability Program). The Canada Green Building Council recommended a $25 million sustainable construction materials grant program in Budget 2024 to build Canadian capacity for the Environmental Product Declarations required by federal buy-clean procurement; it was not funded. A targeted incentive for low-carbon material specification and verification, whether through renewed budget allocation, Housing Accelerator Fund action plan conditions, or CMHC mortgage insurance programs, would address a genuine demand-side gap and let Canadian manufacturers actually compete for federally-supported housing contracts.

3. Quantify low-emission procurement commitments in Build Canada Homes

Build Canada Homes' Investment Policy Framework already commits to prioritizing low-carbon concrete, steel, mass timber, and softwood lumber in its direct procurement and in the projects it finances. This is the right direction but lacks a measurable target. A qualitative preference for "low-carbon materials" leaves too much room for interpretation to drive real substitution at scale. Adding quantified embodied carbon reduction targets, consistent with this study's findings, would convert an aspirational commitment into a procurement criterion suppliers can design toward. The cost analysis in this study shows these targets can be met without compromising affordability, which aligns Build Canada Homes' climate objectives with its core mandate.

4. Invest in domestic bio-based material supply chains

This study's Scenario 3 findings demonstrate that emerging bio-based materials can store more carbon in new housing than is emitted to build it. The feedstocks exist across Canada, but the manufacturing capacity does not.

This is the policy area where the gap between ambition and instrument is largest. The Strategic Response Fund (successor to the Net Zero Accelerator) and the Clean Technology Manufacturing Investment Tax Credit are the closest existing levers, but neither currently covers bio-based construction materials. Extending eligibility to this category, or designating a dedicated stream, would support the wood fiber board mills, hempcrete producers, and cellulose batt lines that would build Canada's domestic capacity. This is industrial policy that doubles as climate policy.

The technical and commercial conditions for deep embodied carbon reduction already exist. What converts that evidence into national-scale emissions reductions is policy direction, set now.

Appendix B: Embodied Emission Scenario Models

The complete scenario models for all six designs, including product-level emissions and storage results, are available upon request.

Appendix C: Full Results by Design and Product Category

ADU 01 — Ontario
	Scenario 1		Scenario 2		Scenario 3		Change vs Scenario 1
Product Category	Emissions (kgCO₂e)	Storage (kgCO₂e)	Emissions (kgCO₂e)	Storage (kgCO₂e)	Emissions (kgCO₂e)	Storage (kgCO₂e)	Emissions S1 vs BL (%)	Emissions S2 vs BL (%)
Wall & Ceiling Finishes	903	0	559	0	763	-2,114	-38%	-15%
Cladding	256	0	199	-1,211	256	-1,236	-22%	0%
Framing	1,003	0	1,003	0	771	-2,754	0%	-23%
Cavity Insulation	666	0	1,146	-1,448	435	-3,528	72%	-35%
Continuous Insulation Above Grade	1,189	0	1,453	-2,688	317	-2,949	22%	-73%
Membranes & Barriers	240	0	171	0	171	0	-29%	-29%
Flooring	382	0	180	0	34	0	-53%	-91%
Concrete	2,663	0	1,896	0	1,971	-900	-29%	-26%
Continuous Insulation Below Grade	481	0	259	0	144	0	-46%	-70%
Aggregate	163	0	163	0	0	0	0%	-100%
Roofing	805	0	450	0	218	0	-44%	-73%
Structural Elements	159	0	78	0	78	0	-51%	-51%
Windows	970	0	970	0	970	0	0%	0%
TOTAL	9,880	0	8,526	-5,347	6,129	-13,480	-14%	-38%

ADU 02 — Alberta
	Scenario 1		Scenario 2		Scenario 3		Change vs Scenario 1
Product Category	Emissions (kgCO₂e)	Storage (kgCO₂e)	Emissions (kgCO₂e)	Storage (kgCO₂e)	Emissions (kgCO₂e)	Storage (kgCO₂e)	Emissions S1 vs BL (%)	Emissions S2 vs BL (%)
Wall & Ceiling Finishes	1,838	0	1,170	0	2,222	-3,552	-36%	21%
Cladding	587	0	467	0	2,283	-5,411	-21%	289%
Framing	1,923	0	1,326	0	3,719	-8,274	-31%	93%
Cavity Insulation	1,291	0	1,132	-2,109	738	-19,747	-12%	-43%
Continuous Insulation Above Grade	1,968	0	2,360	-4,367	2,719	-3,694	20%	38%
Membranes & Barriers	1,164	0	941	0	805	0	-19%	-31%
Flooring	519	0	172	-278	310	-292	-67%	-40%
Concrete	7,060	0	5,997	0	6,093	-1,989	-15%	-14%
Continuous Insulation Below Grade	492	0	221	0	195	0	-55%	-60%
Aggregate	190	0	190	0	155	0	0%	-18%
Roofing	921	0	514	0	514	0	-44%	-44%
Structural Elements	358	0	231	0	231	0	-36%	-36%
Windows	1,139	0	1,139	0	1,139	0	0%	0%
TOTAL	19,450	0	15,860	-6,754	21,124	-42,961	-18%	9%

Fourplex — Ontario
	Scenario 1		Scenario 2		Scenario 3		Change vs Scenario 1
Product Category	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Emissions S1 vs BL (%)	Emissions S2 vs BL (%)
Wall & Ceiling Finishes	6,159	0	4,261	0	4,841	-11,383	-30.8%	-21.4%
Cladding	3,130	0	1,817	-1,480	2,122	-1,922	-41.9%	-32.2%
Framing	10,462	0	4,764	0	4,939	-14,654	-54.5%	-52.8%
Cavity Insulation	4,725	0	5,785	-6,593	2,892	-13,385	22.4%	-38.8%
Continuous Insulation Above Grade	3,657	0	4,614	-8,540	1,035	-9,642	26.2%	-71.7%
Membranes & Barriers	1,337	0	669	0	669	0	-50.0%	-50.0%
Flooring	2,060	0	1,390	-852	1,282	-1,578	-32.5%	-37.7%
Concrete	10,881	0	8,131	0	8,288	-4,506	-25.3%	-23.8%
Continuous Insulation Below Grade	2,451	0	1,258	0	982	0	-48.6%	-59.9%
Aggregate	381	0	381	0	0	0	0.0%	-100.0%
Roofing	1,746	0	976	0	472	0	-44.1%	-73.0%
Structural Elements	636	0	312	0	312	0	-51.0%	-51.0%
Windows	6,356	0	6,356	0	6,356	0	0.0%	0.0%
TOTAL	53,980	0	40,714	-17,464	34,190	-57,068	-24.6%	-36.7%

Fourplex 02 — Alberta
	Scenario 1		Scenario 2		Scenario 3		Change vs Scenario 1
Product Category	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Emissions S1 vs BL (%)	Emissions S2 vs BL (%)
Wall & Ceiling Finishes	6,210	0	4,435	0	6,387	-17,343	-28.6%	2.8%
Cladding	1,200	0	934	0	4,456	-10,768	-22.2%	271.3%
Framing	5,622	0	3,955	0	9,584	-24,971	-29.7%	70.5%
Cavity Insulation	4,770	0	4,015	-6,666	5,698	-21,447	-15.8%	19.5%
Continuous Insulation Above Grade	5,461	0	5,885	-10,890	7,217	-9,805	7.7%	32.1%
Membranes & Barriers	4,273	0	2,500	0	2,260	0	-41.5%	-47.1%
Flooring	2,754	0	1,231	-1,425	1,598	-1,418	-55.3%	-42.0%
Concrete	17,974	0	15,091	0	15,413	-3,819	-16.0%	-14.2%
Continuous Insulation Below Grade	2,401	0	1,187	0	835	0	-50.6%	-65.2%
Aggregate	490	0	490	0	0	0	0.0%	-100.0%
Roofing	2,768	0	1,546	0	1,546	0	-44.1%	-44.1%
Structural Elements	1,009	0	650	0	650	0	-35.5%	-35.5%
Windows	5,376	0	5,376	0	5,376	0	0.0%	0.0%
TOTAL	60,306	0	47,293	-18,982	61,020	-89,571	-21.6%	1.2%

Stacked town 02 — Ontario
	Scenario 1		Scenario 2		Scenario 3		Change vs Scenario 1
Product Category	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Emissions S1 vs BL (%)	Emissions S2 vs BL (%)
Wall & Ceiling Finishes	11,215	0	7,671	0	9,404	-21,163	-31.6%	-16.1%
Cladding	6,219	0	3,605	-2,813	4,025	-3,624	-42.0%	-35.3%
Framing	20,773	0	9,397	0	10,412	-30,092	-54.8%	-49.9%
Cavity Insulation	9,049	0	11,861	-13,343	5,688	-27,559	31.1%	-37.1%
Continuous Insulation Above Grade	7,930	0	9,743	-18,032	2,169	-20,199	22.9%	-72.7%
Membranes & Barriers	2,673	0	1,349	0	1,349	0	-49.5%	-49.5%
Flooring	4,421	0	2,575	-1,625	3,029	-3,926	-41.8%	-31.5%
Concrete	19,457	0	14,544	0	15,271	-8,142	-25.3%	-21.5%
Continuous Insulation Below Grade	4,513	0	2,313	0	1,828	0	-48.8%	-59.5%
Aggregate	668	0	668	0	0	0	0.0%	-100.0%
Roofing	4,158	0	2,324	0	1,124	0	-44.1%	-73.0%
Structural Elements	2,169	0	1,063	0	1,063	0	-51.0%	-51.0%
Windows	7,347	0	7,347	0	7,347	0	0.0%	0.0%
TOTAL	100,594	0	74,461	-35,812	62,710	-114,705	-26.0%	-37.7%

Sixplex — Alberta
	Scenario 1		Scenario 2		Scenario 3		Change vs Scenario 1
Product Category	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Gross Em (kgCO₂e)	Biogenic Storage (kgCO₂e)	Emissions S1 vs BL (%)	Emissions S2 vs BL (%)
Wall & Ceiling Finishes	7,362	0	5,204	0	4,979	-18,316	-29.3%	-32.4%
Cladding	1,272	0	990	0	4,723	-11,414	-22.2%	271.3%
Framing	6,278	0	4,424	0	11,220	-30,448	-29.5%	78.7%
Cavity Insulation	5,439	0	4,568	-7,571	6,539	-23,765	-16.0%	20.2%
Continuous Insulation Above Grade	6,984	0	6,793	-11,752	8,216	-10,561	-2.7%	17.6%
Membranes & Barriers	3,408	0	2,759	0	2,489	0	-19.0%	-27.0%
Flooring	3,163	0	1,383	-1,663	1,814	-1,655	-56.3%	-42.7%
Concrete	20,491	0	17,204	0	17,669	-5,508	-16.0%	-13.8%
Continuous Insulation Below Grade	1,722	0	928	0	516	0	-46.1%	-70.0%
Aggregate	573	0	573	0	0	0	0.0%	-100.0%
Roofing	3,056	0	1,708	0	1,708	0	-44.1%	-44.1%
Structural Elements	1,323	0	649	0	649	0	-51.0%	-51.0%
Windows	7,059	0	7,059	0	7,059	0	0.0%	0.0%
TOTAL	68,129	0	54,240	-20,986	67,580	-101,668	-20.4%	-0.8%