Spray foam insulation under a house typically costs $2,000-$7,000 for a 1,000-square-foot crawlspace, with the price depending on foam type, the surface insulated, access, and local labor rates. Floor joists, crawlspace walls, moisture problems, and removal of old insulation can change the scope substantially.
| Item | Low | Average | High | Notes |
|---|---|---|---|---|
| Installed spray foam | $1,500 | $4,000 | $7,000 | About 1,000 sq ft of accessible underside floor |
| Open-cell foam | $1.50/sq ft | $2.50/sq ft | $4/sq ft | Usually lower-cost; thickness and access matter |
| Closed-cell foam | $2.50/sq ft | $4/sq ft | $7/sq ft | Higher R-value per inch and moisture resistance |
| Old insulation removal | $1/sq ft | $2/sq ft | $4/sq ft | More if contaminated or difficult to reach |
What a 1,000-square-foot crawlspace spray foam job costs
For an accessible crawlspace with roughly 1,000 square feet of floor framing, a common installed range is $2,000-$5,000 for open-cell foam or $3,000-$7,000 for closed-cell foam. National quotes vary, and small jobs can have higher per-square-foot rates because setup and travel costs are spread over less area.
Contractors may price the underside of the floor by the square foot of surface sprayed, not the home’s living-area square footage. Insulating crawlspace walls instead can change both the treated area and the recommended approach. Assumptions: standard residential access, sound framing, no major cleanup, and typical U.S. contractor rates. Confirm which surfaces and foam thickness are included before comparing totals.
How foam, labor, and crawlspace preparation shape the quote
A complete estimate should show the foam system, labor, and any preparation or disposal separately. Ask whether the contractor includes masking, air sealing, cleanup, and inspection of the finished application.
| Quote component | Typical range | What changes the charge | Common unit |
|---|---|---|---|
| Open-cell foam material and application | $1.50-$4 | Thickness, access, and coverage | Per sq ft |
| Closed-cell foam material and application | $2.50-$7 | Required R-value and number of passes | Per sq ft |
| Labor and setup | $500-$2,000 | Crew size, crawlspace clearance, and job length | Per project |
| Removal and disposal | $1-$4 | Old insulation condition and contamination | Per sq ft |
| Air sealing or minor repairs | $150-$800 | Gaps, penetrations, and damaged vapor barrier | Per project |
Crew labor is often estimated at $75-$125 per worker-hour, although bids commonly bundle labor into the installed square-foot rate. Removal, repairs, and moisture control are frequent reasons a low base quote grows.
How crawlspace height and foam thickness change the price
Low clearance raises labor time because installers may need to crawl, reposition equipment, and work around plumbing and wiring. A crawlspace with less than 18 inches of working clearance can cost 10%-30% more than an open, accessible space; standing water or heavy debris may require separate remediation before spraying.
Foam thickness is another major variable. Open-cell foam is commonly applied around 3-6 inches, while closed-cell foam often reaches the target insulation value at roughly 2-4 inches. More material increases cost, and code requirements vary by climate zone and application. Specify the foam type, finished thickness, and intended R-value in writing.
How long installers need beneath the house
A straightforward 1,000-square-foot underside-floor project may take one day for preparation and application, while removal or tight access can extend work to two or three days. A typical crew has two or three installers. Ask whether the quote includes ventilation, occupant-protection measures, and the time required before the area can be re-entered.
Spray foam application requires appropriate protective equipment and controlled conditions. If the crawlspace has active moisture, pest activity, or damaged framing, resolving those issues first can prevent paying to cover a problem that still needs repair. Shorter jobs are not necessarily cheaper if important prep work is omitted.
When removal and crawlspace encapsulation add charges
Old fiberglass or other insulation may need removal before foam can adhere properly. Removal commonly adds $1-$4 per square foot, with higher charges for wet, moldy, or pest-contaminated material. Cleaning or remediation is often quoted separately after inspection, so the estimate should identify its limits.
Spray foam is not the same as full crawlspace encapsulation. A ground vapor barrier, sealed vents, drainage work, or a dehumidifier may add roughly $1,500-$6,000 or more, depending on the crawlspace and equipment. These measures should be priced as distinct work rather than hidden in the foam rate. Request separate line items for insulation, moisture control, and cleanup.
Spray foam versus fiberglass beneath floor joists
Fiberglass batts can cost about $1-$3 per square foot installed when access is easy, making them less expensive upfront than spray foam. However, batts can sag or lose performance if exposed to moisture or air movement. Spray foam costs more but can seal gaps as it is applied; closed-cell foam also resists water better than open-cell foam.
For a dry, accessible crawlspace, a contractor may quote fiberglass or rigid foam as alternatives. For uneven framing, air leaks, or limited clearance, spray foam may be more practical, though suitability depends on building conditions and local code. Compare complete installed prices and expected performance, not material prices alone.
Ways to lower the under-house foam insulation bill
Measure the actual surface to be sprayed and ask contractors to quote the same scope, foam type, thickness, and prep work. Compare at least three itemized estimates; a bid that excludes removal or air sealing is not directly comparable with one that includes those tasks.
Improve access by clearing stored items and arranging safe entry before the crew arrives, if the contractor approves. Avoid paying for thicker foam than the project requires, but do not reduce thickness below applicable code or the agreed performance target. If only a small damaged area needs attention, ask whether a targeted repair is feasible instead of treating the entire crawlspace. Scope consistency and early moisture repairs are the most controllable ways to prevent cost overruns.