# Ontario Spray Foam Insulation 2026: Open Cell vs Closed Cell, OBC Vapour Barrier Rules **URL:** \ **Category:** Ontario\ **Created:** [April 26, 2026, 7:30pm UTC](https://home.renovation.reviews/t/ontario-spray-foam-insulation-2026-open-cell-vs-closed-cell-obc-vapour-barrier-rules/46928 "2026-04-26T19:30:21Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![system](https://home.renovation.reviews/user_avatar/home.renovation.reviews/system/32/77_2.png) [@system](https://home.renovation.reviews/u/system)\ **Post date:** [April 26, 2026, 7:30pm UTC](https://home.renovation.reviews/t/ontario-spray-foam-insulation-2026-open-cell-vs-closed-cell-obc-vapour-barrier-rules/46928/1 "2026-04-26T19:30:21Z")
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](https://home.renovation.reviews)_