Re-evaluating spray foam under the 2025 CMHC Materials Guide.
May 14, 2026
By Mickel Maalouf
The 2025 Canada Mortgage and Housing Corporation (CMHC) Materials Guide, published as part of the Housing Design Catalogue (HDC), is becoming a key reference for affordable housing projects across the country. It catalogs embodied-carbon values, cost, lifespan and biogenic carbon data for a wide range of building materials, giving design and construction teams a common framework for comparing options and aligning with Canada’s climate and housing objectives.
As Canada ramps up efforts to deliver high-performance, low-cost housing, the influence of this Guide will only grow. Its numbers will shape everything from material selection to procurement standards. But as contractors begin applying those figures, it’s worth asking: do they reflect what’s actually being built today?
A case in point: spray foam insulation
The 2025 Guide lists closed-cell spray polyurethane foam (SPF) as having a disproportionately higher embodied carbon value compared to other cavity insulation materials. Indeed, the listed values for several insulation materials, such as mineral wool and fiberglass, are much lower than those typically found in product-specific and industry-wide environmental product declarations (EPDs) on the market. This exaggerates the relative environmental impact of SPF and gives the impression that SPF is a poor environmental choice. But dig a little deeper, and the picture changes.
For instance, the Guide lists global warming potential (GWP) for mineral wool cavity insulation at 1.2 kilograms for a thickness that gives R-21, which translates to 0.33 kg at RSI-1 (RSI-1 = R-5.678). For comparison, the light-density mineral wool industry average EPD declares a GWP around four kilograms at RSI-1, which is much higher than the Guide. Product-specific mineral wool EPDs also declare GWP values between 1.2 and four kilograms at RSI-1. Therefore the GWP values listed in the guide don’t align with product-specific and industry-wide EPD for light-density mineral wool, which makes us wonder where the value comes from.
The same applies for unfaced fiberglass batt. The industry EPD declares a GWP around one kilogram at RSI1 while the Guide declares the same value but at R21 (RSI-3.70), which again makes the listed GWP lower than what’s declared in EPDs.
Note that the Guide lists a GWP value for SPF around 3.23 kg at RSI-1. The current industry EPD for SPF declares a GWP of 2.72 kg at RSI-1. In addition, the SPF industry is currently undergoing a second update to its closed-cell SPF EPD to more accurately reflect the HFO blowing agent’s real carbon impact. The GWP values are expected to be even lower than what’s currently declared. The environmental data from the latest industry EPD should be in the Guide.
The Guide lists the GWP of various insulation materials using a measure of kilograms of carbon dioxide emitted per meter square at an insulating value of RSI-1. Here are the values given in the Guide:
Light-density mineral wool: 0.33
Fibreglass batt: 0.27
Spray foam: 3.23
However our review of product and industry EPDs generated the following average values:
Light-density mineral wool: 1.2 to 4
Spray foam: 2.5 to 2.72 (Expected to be lower once EPDs are updated for current HFO formulations.)
In summary, several insulation materials in the Guide have listed GWP values that seem much lower than what is typically found on the market, which renders SPF’s relative environmental impact disproportionately higher. Today’s SPF products use hydrofluoro-olefin (HFO) blowing agents, which is a major shift in chemistry that cuts global warming potential (GWP) by more than 99 percent, which makes SPF insulation competitive with other materials in terms of embodied carbon. That difference completely changes the carbon profile.
Transition from HFC to HFO: SPF’s lower carbon profile
Under Canada’s Ozone-Depleting Substances and Halocarbon Alternatives Regulations, HFC blowing agents were phased out as part of the Kigali Amendment to the Montreal Protocol. Since then, manufacturers including Huntsman Building Solutions have transitioned fully to HFO technology. All compliant closed-cell spray foam sold in Canada is now HFO-based. These systems deliver the same R-values and airtightness performance, but with a fraction of the embodied climate impact. The GWP of the old HFC foams was between 700 and 1,000. As seen above, the HFO foams come in under three.
This single shift in chemistry cuts embodied emissions by hundreds of kilograms of emitted CO₂ per cubic metre of insulation. Most of the remaining footprint now comes from manufacturing energy and raw materials, not the blowing agent itself. At the same time, HFO spray foams continue to deliver exceptional airtightness, moisture control and thermal performance, which translates into lower heating and cooling loads over decades of building operation.
The bigger picture: whole-life carbon
True low-carbon design means looking at both sides of the ledger: upfront embodied carbon and long-term operational savings. In cold climates, for example, spray foam’s superior air-sealing can reduce heating energy by 20 to 40 percent. Over a 50-year service life, those savings often outweigh the embodied-carbon differences several times over. With today’s HFO chemistry, the carbon payback period – the point where operational savings offset embodied emissions – can be as short as three to seven years. For affordable housing designed to last, that’s a smart and measurable return.
Practical guidance for contractors
Contractors working within the HDC framework can remain fully aligned with CMHC’s sustainability objectives while continuing to specify spray foam. A few key steps help ensure decisions are based on current data:
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- Confirm embodied carbon values – Request documentation of GWP values, either through product-specific or industry-wide EPDs. Make sure all EPDs are up to date to reflect the most current environmental impact;
- Run a carbon payback check – Compare embodied carbon versus annual energy savings. If payback occurs within five to 10 years and the building lifespan exceeds 30, spray foam is typically the lower-carbon choice overall;
- Test airtightness – Include blower-door tests and envelope commissioning to ensure spray foam’s benefits are fully realized;
- Document your approach – Explain the embodied-plus-operational carbon logic in tenders and sustainability reports.
Building affordable housing smartly and accurately
The CMHC Materials Guide is a valuable tool for the industry. But several listed insulation materials seem to have GWP values much lower than what’s found in industry EPDs, which in turn renders SPF’s environmental impact disproportionately higher. When measured with current data, HFO spray foam continues to stand out for its balance of performance, durability, and carbon efficiency that are key traits for the next generation of affordable, energy-efficient housing. As contractors, designers, and manufacturers, we share the same goal: build more homes, faster, and do it responsibly.
