Spray Foam vs Batt Insulation — Ontario Guide

The fundamental difference is that spray foam fills every gap and seals air leaks; batt fills the cavity but does nothing about gaps or air movement. That single difference drives most of the price and performance gap.

Batt is the right choice when:

1. cavity is regular and accessible, clean 16" or 24" o.c. stud bays without obstructions install batt in minutes per cavity
2. cost is the priority, batt is 50-70% cheaper than spray foam at the same R-value
3. DIY is on the table, homeowners can install batt safely with basic PPE, no licensing required
4. soundproofing matters, Rockwool ComfortBatt mineral wool is one of the best products for STC-rated party walls and home theatre rooms
5. you'll renovate again later, batt is easy to remove during future re-wiring or plumbing changes
6. you're meeting OBC R-22 in a 2x6 wall, easy with batt, no premium needed.

For most basement framing and standard wall assemblies, batt is correct.

Spray foam is the right choice when:

1. air sealing matters, older Toronto homes losing 30-40% of heat through air leaks see massive heating bill improvements with spray foam
2. shallow cavities limit batt R-value, 2x4 walls hitting R-22 require spray foam (no batt product gets there in 3.5")
3. the assembly is irregular, basement walls with stone/rubble foundations, rim joists with offset framing, cathedral ceilings with intricate roof geometry
4. you need both insulation and vapour barrier in one pass, closed-cell at 2" gives both, eliminating poly sheet labour
5. below-grade or moisture-prone, closed-cell rejects water, batt absorbs it
6. high-performance whole-home retrofits where every R-point and air-leakage improvement counts toward Greener Homes grant max.

Spray foam's premium pays off most in retrofit situations where air sealing has the biggest dollar impact.

Cost differences widen on whole-home jobs but narrow on small specialty cavities where batt's labour overhead grows.

Many Ontario high-performance builds use both: 2-3" of closed-cell spray foam against the structural element (sheathing, foundation, roof deck) for air and vapour control, then batt or blown-in fill for the bulk R-value. This hybrid approach delivers spray-foam-quality air sealing at 60-70% of pure spray foam cost.

For a 2x6 wall in a new build, a typical high-performance assembly is 2" closed-cell foam against the sheathing (R-13 + air + vapour barrier) plus 3.5" mineral wool batt in the remaining cavity (R-15). Total R-28, exceeding OBC R-22 minimum, with cost roughly halfway between pure batt and pure foam. We see this assembly increasingly in custom builds across Toronto and Vaughan.