You want spray foam in the attic, but one quote measures the floor and another measures the underside of the roof. Those prices can describe very different jobs before the foam type even enters the comparison.
So RetroFoam of Michigan publishes rough attic roof-deck project prices of $5,900 to $12,000. Its crawlspace examples are $3,000 to $4,500. These are local project ranges before discounts or rebates.
I checked the provider pages on October 23, 2026. I will explain the different project scopes, show how board feet work and compare dated owner quotes without treating them as current offers.
Which Part of the Building Are You Insulating?
The Michigan contractor’s cost page covers its service area, including Michigan’s Lower Peninsula and Greater Toledo. It does not attach one standard building size to every range.
Ask which surfaces the contractor measured. Roof slopes, gables, walls and the rim joist should be identified, rather than bundled under an unexplained description such as attic insulation.
The same page prices injection foam for existing walls separately. I have left that process out of the spray-foam table so an existing-wall injection quote does not become a sprayed-wall price.
If you are replacing loose-fill insulation or batts, my attic insulation replacement guide covers removal and those materials. Its floor-area figures are a different comparison from spraying the roof deck.
Square Feet and Board Feet Are Different
Smart Foam in Wisconsin defines one board foot as one square foot at one inch thick. Measuring only the surface area leaves out the depth of material being installed.
For an illustrative 500-square-foot surface, 500 x 1 inch = 500 board feet. At three inches, 500 x 3 = 1,500 board feet. Those are volume calculations, not recommended depths or a project price.
Ask the installer to write down the product, open-cell or closed-cell type, measured surface area and specified installed thickness. A board-foot figure without those details is hard to check.
The worker photographs illustrate spray application in different buildings. Neither photograph shows a priced Michigan job, and the visible application is not a specification for your house.
Older Owners’ Quotes Show Why Scope Matters
These three US members wrote in a Garage Journal spray-foam discussion in February 2013. Their figures are historical comparisons, not today’s installed prices.
- Northern Illinois member 78C-10, February 11: a $3,200 quote for two-inch closed-cell foam on the walls and gables of a 30 x 40 x 10-foot building. The ceiling was excluded.
- Northern Illinois member zeebad1, February 11: $14,000 paid for two inches on sidewalls and three inches on the roof. The post does not supply the building dimensions.
- Republic, Missouri member BrianC636, February 12: around $5,500 paid for a 40 x 64 x 12-foot building, with four-inch open-cell walls and six inches at the roof deck. Combining work with the house helped the deal.
The Illinois wall-only quote cannot establish a whole-building price. The Missouri job also used a different foam type and thickness, so dividing these totals by floor area would hide important differences.
Preparation Can Change the Proposal
Have the installer identify old insulation removal, disposal, access and surface preparation as included or separate. A proposal to spray an accessible empty building differs from work around an occupied home’s contents.
Ask how the design handles the attic or crawlspace as a whole, including existing ventilation and any required protective covering. Have the installer explain which related work is included in its price.
For a crawlspace with dampness or damage, my crawlspace repair guide covers other project scopes. Foam installation should not be mistaken for a complete moisture or structural repair package.
Request the product’s written ventilation and reoccupancy instructions before arranging the work. The quote should name who provides those instructions and how the job will be handed back to you.
How I Would Compare Two Foam Quotes
First match the surfaces and foam product. Then compare the thickness, material quantity, preparation, protective work and cleanup. Ask how any extra material or inaccessible areas would be charged.
Keep rebates or promotional discounts separate from the starting project price. The Michigan ranges above are before those reductions, so a discounted proposal needs its own clear breakdown.
Questions About Spray Foam Prices
How much does spray foam insulation cost for an attic?
RetroFoam of Michigan publishes roughly $5,900 to $12,000 for attic roof-deck projects in its market. The measured roof surface, product, thickness and preparation need confirming for your property.
Is one board foot the same as one square foot?
Only at one inch thick. Smart Foam defines a board foot as one square foot at one inch. A 500-square-foot surface at three inches uses a calculated 1,500 board feet.
Can I compare open-cell and closed-cell quotes by total price?
First match the intended design, surfaces and specified thickness. The older owner examples use different products and depths, so their whole-building totals do not establish an equivalent material price.
Does the attic range include removing old insulation?
Do not assume that. Have the contractor identify removal, disposal, preparation and any related protective work as included or separate in the written quote.
Where These Foam Prices Come From
US contractor pages checked October 23, 2026. The owner examples retain their February 2013 dates and quote or paid status.
- RetroFoam of Michigan: local spray-foam project ranges and separate injection-foam scope
- Smart Foam: board-foot definition
- Garage Journal: Illinois and Missouri owners’ dated project descriptions
I hope this helps you compare the same insulation job. You can share a recent itemized US quote at costcheckr@gmail.com.
