Spray foam bid calculator

How much to charge for spray foam insulation

A published “$3.50 / sf of attic” special prices the floor. Residential spray foam is not the floor. It is board feet — square feet times inches — plus a closed-cell rim the coupon never counted, plus an ignition coating on exposed foam. Matching the coupon on an 8-inch open-cell attic with a rim is how a sold job becomes a drum-short loss after the first bay.

The number an attic-square-foot special cannot see

Take a 40×30 attic, 8 inches of open-cell, no rim, no coating. That is 1,200 square feet of plane and 9,600 board feet — 10,560 after 10% waste. The coupon says $3.50 × 1,200 = $4,200. Foam at a starting $0.55 per board foot is already $5,808 before labor. Raise the same shop to an 80-foot closed-cell rim and an intumescent coat. The attic is still “about 1,200,” so the coupon barely moves. The job did not: 185 board feet of closed-cell, coating on 1,200 square feet, and rim hours the 8-inch floor never had.

Put 5.5 inches of closed-cell on a 6/12 cathedral. Closed-cell is a different drum and a different rate. Pitch-adjusted roof area is not attic floor. $3.50 per square foot of floor is not a closed-cell price.

How to price it

1. Measure the sprayed plane. Attic floor is length times width. Cathedral multiplies by a pitch factor.
2. Count board feet: square feet times inches. Add rim board feet. That sum is what drums are sold in.
3. Split open-cell and closed-cell. Hybrid is one inch closed plus open-cell fill. Waste is higher on open-cell.
4. Price ignition coating, access, mobilization, and the permit allowance.
5. Load the wage, add foam and coating, mark overhead on direct cost, then divide by one minus the target margin. The walk-away price is total cost.

The spray foam bid calculator does that arithmetic in the browser from your own hours and invoices. Starting cell rates, waste percents, and material rates are ballpark figures to replace, not a drum quote or a code table.

What this is not

This is not an energy-code opinion, a permit, a construction specification, a manufacturer warranty, or an engineering stamp. Confirm the jurisdiction, the assembly, and a qualified professional before sending a price. The output is arithmetic on the numbers you typed.

No warranty. This free article and calculator are not construction, legal, tax, financial, or engineering advice. To the maximum extent permitted by law, the authors accept no liability for loss or damage from their use.

Common questions

How much to charge for spray foam insulation?

Start from the sprayed plane, count the board feet an attic-square-foot special cannot see, then add cell type, rim-joist footage, ignition coating, waste, and the permit. A published $3.50 per square foot special only sees attic floor.

Why do board feet and rim joists change the price?

A 1,200 square-foot attic at 8 inches of open-cell is 9,600 board feet. An 80-foot rim at 9.25 inches sprayed 3 inches is another 185 board feet of closed-cell the attic coupon never counted. Matching the coupon is how the rim job loses money.

Is this an energy-code calculation?

No. Cell rates, waste percents, and hours here are common starting points on residential bids. They are not an energy-code opinion, a permit, a manufacturer warranty, or an engineering stamp.

See this calculator vs. a flat per-square-foot attic price for what the coupon method above gets wrong on a rim or a cell switch, spelled out side by side.