Spray foam insulation
Spray foam insulates and air seals in one step. That makes it the right material in specific places — and an expensive overkill in others. Here is where it actually earns its cost.
Closed-cell vs open-cell
| Closed-cell | Open-cell | |
|---|---|---|
| R per inch | ~R-6.5 to R-7 | ~R-3.6 to R-3.8 |
| Vapor barrier | Yes at 2"+ | No |
| Water resistant | Yes | No |
| Adds structural rigidity | Yes | No |
| Cost per board foot | $1.25 – $2.00 | $0.45 – $0.90 |
For most Minnesota applications — rim joists, crawlspaces, below-grade, cathedral ceilings — closed-cell is the correct product because it handles moisture and hits high R in a thin cavity. Open-cell makes sense in interior sound-deadening walls and in deep attic applications where cost matters more than moisture control.
Where foam is worth the money
- Rim joists — the single best foam application in any Minnesota house
- Cathedral and vaulted ceilings — no room for R-49 of blown material, and no vent channel
- Crawlspaces — walls and rim, as part of encapsulation
- Bonus rooms over garages — the classic freezing-floor room
- Cantilevers and overhangs
- Additions and new framing where the wall is open anyway
- Odd geometry — trusses, chases, and framing that batts cannot fill cleanly
Where it usually is not
An open attic floor. You can hit R-60 with blown cellulose for a third of the cost of foam, and the attic floor is easy to air seal separately. Foam belongs where you cannot get depth or where you need moisture control.
Planning ranges (Twin Cities, estimates)
| Work | Typical range |
|---|---|
| Closed-cell, per board foot | $1.25 – $2.00 |
| Open-cell, per board foot | $0.45 – $0.90 |
| Rim joist, average home | $1,200 – $2,800 |
| Cathedral ceiling, 600 sq ft | $4,000 – $8,000 |
| Crawlspace walls and rim | $3,000 – $7,500 |
| Bonus room over garage | $2,500 – $6,000 |
Estimates for planning.
Practical notes
Foam is installed to a temperature range and needs the space vacated during application and curing — typically 24 hours. It expands hard enough to bow framing if over-applied, so lift thickness matters. And once it is in, it is in; plan wiring and plumbing runs before the foam, not after.
What's included
- Free, no-pressure estimate
- Licensed & fully insured crew
- Cleanup included — we leave it spotless
- Same-day or scheduled service
- Written quote, fair pricing
- 24/7 emergency response
FAQ
Is spray foam worth the extra cost?
In rim joists, crawlspaces, cathedral ceilings, and cantilevers, yes — nothing else insulates and air seals in a thin cavity. On an open attic floor, blown cellulose to R-60 delivers more R per dollar.
Do I need to leave the house during installation?
You should stay out of the work area during application and for about 24 hours after while it cures and off-gasses. Whole-house evacuation is not usually needed for a small area like a rim joist.
Closed-cell or open-cell for a Minnesota basement?
Closed-cell. It resists moisture, acts as its own vapor retarder above two inches, and hits high R in the depth available below grade.
Can spray foam cause moisture problems?
Done correctly it prevents them by stopping moist air movement. Problems come from spraying over wet framing or trapping water where a leak already exists, so the leak gets fixed first.
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