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Install Crawl Space or Basement Insulation

If your floors are cold to the touch, it may be time to insulate the crawl space, basement or garage. Insulating these spaces increases the comfort level in your home, decreases heating and cooling expenses and dampens noise.

Insulate your Crawl Space

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Insulate Your Crawl Space or Basement


Wear a dust mask, gloves and goggles when working with insulation.


Step 1

R-values US map.

Determine the R-value required in your area with the map and corresponding key in Step 2 or by contacting your local contractor or building inspector.

Good to Know

R-values measure heat resistance. Higher values indicate greater insulating power.

Step 2

R-values chart.

Locate your area's corresponding color on the chart to identify your insulation needs.

Step 3

Measure the distance between floor joists to determine whether you need 15-inch-wide or 23-inch-wide insulation.

Step 4

Use our insulation calculator to determine how much insulation you need.

Step 5

Determine the number of insulation supports needed: Divide the square footage of insulation required by 4 for 15-inch-wide insulation and by 5 for 23-inch-wide insulation.

Step 6

Seal any cracks leading into the home's interior with caulk or spray foam.

Step 7

Spread the polyethylene over the entire crawl space or basement floor. Overlap any seams by 16 inches to 24 inches and secure with duct tape. The polyethylene acts as a vapor (moisture) barrier to prevent excess ground moisture from permeating the insulation.

Step 8

Start at one edge of the crawl space or basement and install insulation between the joists with the vapor barrier up. The insulation should fit snugly between the joists. If you need to cut the insulation, turn the faced side up, compress the insulation with a straight edge, and cut with a utility knife. Install wire insulation supports every 24 to 36 inches to hold the insulation in place.

Good to Know

Because roll insulation is highly compressed, don't take the wrapping off until you get the roll to the installation area.

Step 9

Continue installing the insulation until the entire area to be insulated is covered.

Step 10

Stuff small pieces of insulation into areas around obstructions, such as pipes or drains. Use a broom handle to stuff the insulation into hard-to-reach places.

Step 11

If you install insulation in basement or garage walls, cover the areas with drywall to protect the insulation's integrity.

Insulating a Garage Door

Further reduce drafts in your basement or garage with foam board insulation and weatherstripping.