Is Spray Foam Insulation Worth It? Open-Cell vs Closed-Cell, the Risks, and Rebates Today
Closed-cell foam delivers high R-value and doubles as an air and vapour barrier — but it must be installed correctly by a certified pro; done wrong, it off-gasses and can trap moisture in the wall
Is spray foam insulation worth it, and how do you choose between open-cell and closed-cell?
Yes — if you pick the right type and have it installed correctly by a certified pro. There are two kinds: open-cell at about R-3.5–4 per inch (industry figure), good for interior partitions/soundproofing and lower cost; and closed-cell at about R-6–7 per inch (industry figure), which is insulation + air barrier + vapour/secondary water barrier in one, good where space is tight or moisture control matters. The key risk: in Canada installers must be third-party certified (e.g., CUFCA); off-ratio mixing or spraying in damp/cold conditions can leave foam that never fully cures and keeps off-gassing, and it can trap moisture in the assembly. The Ontario Building Code generally requires a thermal barrier (e.g., half-inch drywall) over foam.
Sources: CUFCA (Canadian Urethane Foam Contractors Association); CAN/ULC-S705.1/.2 and NRC-CCMC standards; Ontario Building Code (thermal/ignition barrier requirements; article numbers vary by edition); Natural Resources Canada and Enbridge Gas (rebate status, reviewed 2026). R-values are industry figures.
Spray foam has been popular for a few years — great R-value and it seals up air leaks. But it’s also one of the few materials that’s hard to fix if it goes in wrong: bad ratio or conditions and it keeps off-gassing, and once closed-cell foam traps moisture in a wall, framing can rot out of sight. Here’s how to choose open-cell vs closed-cell, the real risks, why you must use a certified installer, what the code requires for fire, and whether any rebates still exist.
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Two foams: choosing open-cell vs closed-cell
The biggest risk is the install, not the material
⚠️Use a CUFCA-certified installer. According to CUFCA, spray-foam installation in Canada must be third-party certified with annually renewed ID. Wrong ratio or conditions can leave foam that won’t cure and keeps off-gassing — one of the hardest problems to fix after the fact, so get the contractor right up front.
In Canada: installers must be certified
ℹ️Don’t budget rebates off the old program. The federal Greener Homes Grant closed at the end of 2025; Ontario’s current path is the Home Renovation Savings (HRS) program for insulation rebates. Confirm current amounts and eligibility on the official page before you budget.
Fire code: a thermal barrier over the foam
Moisture, inspectability, and rebates today
Frequently Asked Questions
How do I choose open-cell vs closed-cell foam?
By location and budget. Closed-cell (about R-6–7/inch, industry figure) doubles as air and vapour control — good where space is tight or moisture matters (basements, roofs); open-cell (about R-3.5–4/inch) is lower density and cost, good for interior partitions and sound. Pricier isn’t automatically better — match it to the job.
Will spray foam keep smelling?
Well-cured foam off-gasses minimally. Persistent odour is usually an installation problem — off-ratio mixing or spraying in damp/cold conditions so the foam doesn’t fully cure. That’s why a CUFCA-certified installer working in the right conditions, getting it right once, matters most.
Do I still need drywall over spray foam?
Usually yes. Under the Ontario Building Code, foamed plastics exposed to interior space generally need a thermal barrier (commonly half-inch drywall) for about 15 minutes of fire protection; attics/crawl spaces may allow an ignition barrier instead. Confirm the exact requirement against the current code — don’t leave foam exposed.
Are there still rebates for insulation?
The federal Greener Homes Grant closed at the end of 2025; in Ontario the Home Renovation Savings (HRS) program has taken over and currently offers insulation rebates. Confirm current amounts and eligibility on enbridgegas.com.
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