Spray foam attic & wall cost calculator
When a contractor prices spray foam per square foot at a set depth, you do not need board-feet — just the area and their $/ft². This runs the job and adds a cushion for the real world.
Calculator
Spray foam over 1,000 ft² at $2.50/ft² is about $2,750.00 with 10% contingency. The $/ft² depends on the depth and R you spray — enter your own quote.
Formula
total = area × $/ft² × (1 + contingency)
This is the per-square-foot path. If your quote is per board-foot instead, use the board-foot cost tool so depth is counted explicitly.
Worked example
A 1,000 ft² attic quoted at $2.50/ft² for the depth you need is 1,000 × $2.50 = $2,500. Add a 10% contingency and budget $2,750. That $/ft² is not fixed — deeper foam for a higher R pushes it up, so make sure the price you enter is quoted at the depth you actually want.
Sanity-checking a per-ft² quote
The trap with $/ft² pricing is that it hides the depth. Two things to nail down:
- What depth / R is that price for? A $2.50/ft² number for 2" of open-cell is a different job from $2.50/ft² for 3" of closed-cell. Confirm the depth and R behind the rate before you compare quotes.
- Attic vs wall. Open attic decking sprays fast and cheap; a cut-up roofline, kneewalls or a cathedral ceiling cost more per square foot for the same area. Price the roofline geometry, not just the footprint.
- Prep and removal. Clearing old insulation, masking and baffling for ventilation are labor that a clean $/ft² can bury — ask whether they are included.
- Cross-check. Convert the area and depth to board-feet and re-price it per board-foot; if the two paths disagree a lot, the quote is carrying extra you should itemize.
Roof covering, ventilation baffling and any moisture detailing sit outside this estimate — those belong to the roofing trade, the data sheet and local code.
Reference table
| Foam | Typical installed $/ft² (labeled) |
|---|---|
| Open-cell spray foam | $1.00–$2.50/ft² |
| Closed-cell spray foam | $1.50–$4.50/ft² |
A labeled sanity band only — the depth and R you spray drive the real number. Enter your own quote above.
Frequently asked questions
How much does it cost to spray foam an attic?
At a typical $/ft² for the depth you need, a 1,000 ft² attic runs on the order of $2,000–3,000 before contingency — but the depth and R drive the rate. Enter your own quoted $/ft² for a real figure.
Per square foot or per board-foot — which should I use?
Use whichever your quote is written in. Per-ft² is quickest when the depth is fixed; per-board-foot is better when you are choosing the depth yourself. This tool is the per-ft² path.
Why add a contingency?
Spray jobs run into overspray, trim, access surprises and prep. A 10% cushion keeps the budget honest; drop it toward 0 only if your quote is genuinely all-in and fixed.
Does this cover the roof itself?
No. This is the thermal insulation cost only. Roof covering, sheathing and ventilation are separate work — the roofline geometry can change the price, so confirm what the quote includes.