Crawl Space Insulation
Proper crawl space insulation keeps floors warmer, reduces energy bills, and improves comfort. Costs range from $1,000–$4,000 depending on size and insulation type.
Insulation Types & Costs
Fiberglass Batt (Floor Joists)
$1.00–$1.50/sq ftR-Value: R-11 to R-30
Rigid Foam Board (Walls)
$1.50–$2.50/sq ftR-Value: R-10 to R-25
Spray Foam (Walls/Floor)
$2.50–$5.00/sq ftR-Value: R-6 to R-7 per inch
Where to Insulate: Floor vs. Walls
Vented Crawl Space → Insulate the Floor
In a vented crawl space, insulate between the floor joists (the subfloor). Use fiberglass batts or rigid foam boards. The crawl space itself remains unconditioned.
Sealed Crawl Space → Insulate the Walls
In a sealed/encapsulated crawl space, insulate the foundation walls instead. This conditions the entire crawl space and is more energy-efficient overall.
Frequently Asked Questions
What is the best insulation for a crawl space?
For sealed crawl spaces, rigid foam board (XPS or polyiso) on the foundation walls is the best option. It resists moisture, provides high R-value per inch, and does not sag. For vented crawl spaces, closed-cell spray foam on the subfloor is ideal but fiberglass batts are a budget alternative.
Should I insulate the floor or the walls of my crawl space?
If your crawl space is vented, insulate the floor (between joists). If it is sealed or encapsulated, insulate the foundation walls instead. Wall insulation in a sealed crawl space is 15 to 20 percent more energy efficient than floor insulation in a vented one.
How much does crawl space insulation cost?
Crawl space insulation costs $1,000 to $4,000 depending on type and size. Fiberglass batts run $1.00 to $1.50 per square foot, rigid foam $1.50 to $2.50, and spray foam $2.50 to $5.00 per square foot installed.
Get Free Quotes
Compare prices from local crawl space professionals. No obligation.