The cost to spray foam an attic depends on its size, the target R-value, and whether you use open- or closed-cell - so the honest way to think about it is board feet, not a flat number. Here's how to estimate an attic before you talk to anyone.
What drives an attic quote
- Size: attic square footage x thickness = board feet.
- R-target: R-38 is about 6" closed-cell or 11" open-cell - a real cost difference.
- Vented vs unvented: air-sealing the flat ceiling and topping with blown-in (hybrid) often costs less than foaming the whole roof deck.
Open or closed for an attic?
Vented attic on a budget: air-seal with foam, then blown-in. Unvented roof deck or cathedral: closed-cell. The right call changes the price.
Estimate it
Run the calculator for your attic's board feet, then get an exact quote. See attic spray foam.