Insulating a Crawl Space

Why install insulation in a crawl space? A crawl space is an unfinished, accessible area below the ground floor of a building. Proper insulation can help protect your living space from outside temperature changes and cold or hot air moving in through the bottom of a house.

There are two types of crawl spaces: vented and unvented. Vented crawl spaces open to the outside, while an unvented crawl spaces is part of the basement – finished or unfinished.

In a vented crawl space, the underfloor should be insulated — similar to how it is in ceilings. This may be done before or after the subfloor has been installed. JM ComfortTherm®, Kraft-faced and unfaced insulation are all possible products to use for this application. With Kraft-faced insulation, the facing is generally against the subfloor.

In an unvented crawl space, you should insulate the perimeter walls.

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Recommended Products

Unfaced Batts & Rolls

JM Unfaced Formaldehyde-free™ fiberglass insulation offers R-values ranging from R-11 to R-38, as well as effective thermal and noise control.

AP™ Foil

AP™ Foil-Faced Polyiso Foam Sheathing provides continuous insulation for maximum efficiency, as well as exceptional moisture, heat and air control.

Kraft-Faced Batts & Rolls

JM Kraft-faced Formaldehyde-free™ fiberglass insulation offers R-values ranging from R-11 to R-38, is ideal for moisture control in exterior walls and provides excellent temperature and noise control.

TempControl® Mineral Wool

JM TempControl® Mineral Wool insulation is made from high-density, noncombustible fibers that helps delay the spread of fire in exterior walls, basements, and heated crawl spaces.

Related How-To Guides

Install in a Crawl Space

This video will take you through the steps you’ll need to insulate a crawl space.

Install Around Objects

This video will guide you through the process of placing insulation around recessed lighting and other areas where you’re likely to encounter obstacles like electrical wiring, plumbing and air ducts.