Crawl Space Insulation Checklist: What to Inspect Before You Insulate

Moisture and drainage

☐ Standing water or damp soil anywhere on the crawl floor — fix drainage first (regrade, gutters, downspout extensions, interior perimeter drain if needed).

☐ Efflorescence, rust, or water staining on foundation walls indicating past bulk water intrusion.

☐ Relative humidity above 60% on a summer day — encapsulation + dehumidifier is required, not optional.

☐ Sump pump present and working, if the crawl sits at or below the water table.

Vapor and air control

☐ Existing vapor barrier torn, folded, or missing at seams and piers.

☐ Open foundation vents — modern practice is to seal them once encapsulated in humid climates.

☐ Rim joist uninsulated or gapped — the single largest air leak in most homes.

☐ Duct joints in the crawl leaking (mastic missing, tape peeling) — seal before insulating around them.

Framing and pest damage

☐ Rotted joists or sill plate — repair or sister before insulating over them.

☐ Active termite, carpenter ant, or rodent activity — pest control first, then insulate.

☐ Insulation batts hanging down, wet, or contaminated — remove and dispose before new work.

☐ Knob-and-tube wiring or older ungrounded circuits — some products cannot legally be installed over these.

System choice

☐ Vented crawl in a dry climate → fiberglass batts between floor joists with kraft facing up.

☐ Vented crawl in a humid climate → encapsulate first, then insulate the foundation walls, not the floor above.

☐ Encapsulated crawl → closed-cell spray foam or rigid foam on foundation walls, R-13 to R-19 depending on climate zone.

☐ Rim joist → 2" closed-cell spray foam regardless of the crawl strategy chosen.

Contract and warranty

☐ Written scope specifying material, R-value, and square footage.

☐ Vapor barrier thickness (min 10-mil for encapsulation) written in the contract.

☐ Dehumidifier make, model, and drain plan if required.

☐ Workmanship warranty of at least 5 years on encapsulation seams.

☐ Certificate of Insurance and state license number provided before work begins.