Spray polyurethane foam (SPF) is increasingly the performance choice for Ontario high-efficiency renovations. Key distinction: open cell vs closed cell.
Open-cell SPF (0.5 lb density):
- R-3.7/inch, lower cost, vapour-permeable
- Good for interior wall cavities, soundproofing
- Not a standalone vapour barrier in Ontario’s cold climate
Closed-cell SPF (2 lb density):
- R-6/inch, rigid, very low vapour permeance
- Acts as its own vapour retarder at 2"+ thickness
- Required for below-grade applications, unvented roofs, moisture-critical assemblies
OBC vapour barrier note: Closed-cell foam can substitute for separate poly vapour barrier in specific assemblies – but the design must be verified for compliance.
Common Ontario applications and GTA costs (2026):
| Application | Cost |
|---|---|
| Rim joist (closed-cell, 2", full perimeter) | $1,000-$3,000 |
| Basement walls (closed-cell, 2", full perimeter) | $6,000-$14,000 |
| Open-cell wall cavities (full house retrofit) | $8,000-$18,000 |
| Closed-cell unvented attic | $3-$7/sq ft |
Critical: Occupants must vacate 24-48 hours post-application. Off-ratio mixed foam never fully cures and poses off-gassing risk indefinitely.
Building science and insulation questions at home.renovation.reviews