Spray polyurethane foam is the highest-performance insulation option for Ontario homes. This thread covers costs, applications, and important considerations for 2026.
Open-Cell vs. Closed-Cell
Open-cell: R-3.5-4/inch, $1.50-$2.50/sq ft (3 inches), vapor-permeable, excellent air sealing, lower cost.
Closed-cell: R-6-7/inch, $2.50-$5/sq ft (2 inches), vapor barrier properties, structural strength addition. Required for below-grade applications in Ontario.
Best Applications
- Crawl space walls and rim joists: closed-cell required
- Cathedral ceilings: closed-cell
- Basement walls: closed-cell
- Attic hatch and drop soffits: either
2026 Cost Benchmarks
- Rim joist (full perimeter): $800-$2,000
- Cathedral ceiling per 1,000 sq ft: $4,000-$9,000
- Full basement walls (1,500 sq ft): $6,000-$14,000
Important Caveats
Must be covered with fire barrier (drywall) in habitable spaces per OBC. Off-gassing requires 24-48 hour evacuation during curing. Permanent installation - cannot be removed without destroying surrounding assembly.
LF Builders coordinates insulation for all renovation projects: https://lfbuilders.ca
Share spray foam project experience at https://home.renovation.reviews