Glossary · Insulation & windows
Spray foam (open-cell and closed-cell)
Also called: spray foam insulation · spray polyurethane foam · open-cell foam · open-cell spray foam · closed-cell foam · closed-cell spray foam
Liquid foam sprayed in place that expands to insulate and air seal in one step; closed-cell is denser and higher R, open-cell lighter.
What it means
Open-cell foam (about 0.5 lb per cubic foot) is soft and airtight at normal thickness but lets vapour through. Closed-cell foam (about 2 lb per cubic foot) is rigid, gives roughly R-6 per inch, resists water and acts as a vapour retarder at about 2 inches. Both are combustible and normally need a fire-protective covering, and installation is a job for certified contractors.
Why it matters in an audit
Spray foam is a strong option for awkward spots like rim joists and cathedral ceilings, but the type and thickness must suit the location and its moisture conditions.
Typical numbers
Reference values with their sources. Your energy advisor’s report gives the figure for your own house.
| What | Value | Source |
|---|---|---|
| R per inch (NRCan) | Open-cell R-3.6–3.8 (design R-3.6); closed-cell R-5.5–6.5 (design R-6) | natural-resources.canada.ca ↗ |
| Aged values and vapour permeance (DOE Building America guide) | Open-cell about R-3.6/in, 10 perms at 5 in; closed-cell about R-6.1/in, under 1 perm at 2 in | www1.eere.energy.gov ↗ |
In Canada
NRCan recommends a certified contractor for polyurethane spray foam and covering it with fire-resistant material where it's left exposed.