Spray foam delivers the best combination of R-value and air sealing in Ontario homes. Here is a complete 2026 guide.
Open Cell vs Closed Cell
Open-cell (R-3.5/inch): Softer, vapour-permeable, less expensive. Interior walls and ceilings. Closed-cell (R-6/inch): Dense, rigid, vapour barrier. Rim joists, cathedral ceilings, basement walls, exterior applications.
Best Applications in Ontario Homes
Rim joists: 2 inches closed-cell = R-12 plus complete air seal. Highest return spray foam application in Ontario basements. Cathedral ceilings: Closed-cell prevents moisture accumulation in thin roof assemblies. Basement walls: Closed-cell provides vapour barrier and insulation in one product. Attic penetrations: Seal around pot lights, plumbing, and mechanical penetrations before blowing attic insulation.
Air Sealing Value
Air infiltration accounts for 25-40% of Ontario home heat loss. Spray foam creates an air barrier that batts and blown insulation cannot match. Air sealing at rim joists and top plates is one of the highest-return energy upgrades available to Ontario homeowners.
Costs in Ontario 2026
Rim joists full perimeter: $800-$2,500. Attic air sealing at penetrations: $1,500-$4,000. Cathedral ceiling full spray: $4-$8/sq ft. Closed-cell wall application: $3-$6/sq ft.
Safety
24-hour re-occupancy period required after application. All spray foam must be covered by drywall or fire-rated thermal barrier in finished spaces per Ontario Building Code.
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