← Attic insulation bid calculator
Enough to cover the bags the R-value delta actually buys, not enough to match the cheapest postcard on the block. An attic already at R-30 going to R-38 is not the same job as the same attic sitting at R-13 going to R-49, and a flat price per square foot cannot see the difference.
Open the free bid calculatorStart with length × width on each attic section. Write down the existing R — depth times the product already in the bays, or a measured inch count converted with that product’s R-per-inch — and the target R the homeowner asked for. Inches to add equal the difference divided by the R-per-inch of the bag you will blow. Cubic feet equal area times those inches divided by 12. Bags equal that volume rounded up to the settled yield printed on the bag. Cellulose, blown fiberglass, and mineral wool are different truckloads.
A blow on top of leaky penetrations is a photo for the homeowner, not an R-value they will feel. Each can light, plumbing stack, and wire hole is foam and time. Baffles at the eaves keep the soffit open and keep the blow from choking the intake. A hatch without a dam becomes a snowdrift in the hallway. If those lines are “included” in a $1.50-a-foot special, they are unpaid.
Loose-fill does not belong on a cathedral ceiling. Count that area so the homeowner sees why it is not in the bag count, then bid dense-pack or foam separately. Wet, compressed, or the wrong product is removal plus a dumpster, not a free upgrade. Contractors who quote only the blow and “figure the rest in” are guessing the line that most often blows a postcard special.
A blower paid $32 often costs more than $41 once employer taxes, respiratory workers’ compensation, liability, and paid time off are counted. Overhead sits on top of that direct cost. Margin is a share of the price the customer sees, not a markup you add last and forget. The walk-away number is total cost: below it the job makes nothing, even before you pay yourself.
This is not a manufacturer coverage chart, not an energy-code requirement, and not a finding that an attic is airtight, permitted, or rebate-eligible. The starting R-per-inch, bag yields, and hours are ballpark numbers so a contractor can see the shape of a bid. Replace them with the bag you buy and times from your own jobs, confirm measurements on site, and have a qualified professional review anything that has to be signed, inspected, or rebated.
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Charge the bags and hours the job will actually take — attic floor area times the inches implied by target R minus existing R, divided by the cubic feet you get from a bag, plus air-sealing penetrations, baffles, travel, and a dumpster if you are pulling existing fill — then divide cost by one minus your target margin. A flat price per square foot hides the difference between topping R-30 to R-38 and taking R-13 to R-49.
Bags come from volume, not floor area. Inches to add equal (target R minus existing R) divided by the product's R-per-inch. Cubic feet equal area times those inches divided by 12. Divide by the settled cubic feet printed on the bag you actually buy, and round up. Cellulose, blown fiberglass, and mineral wool have different yields, so the same attic is a different truckload.
No. Starting R-per-inch, bag yields, and hours are editable ballpark numbers, not a manufacturer coverage chart, an IECC climate-zone table, or a finding that any attic is airtight, permitted, or rebate-eligible. Confirm measurements and product charts on site.