How to Heat a Crawl Space

Heated Crawl Space

Crawl spaces seem to be a source of controversy in the housing community. How to heat them, how to vent them, and how to insulate them are all issues that are being worked through. Homes over the last 50 years were built with crawl spaces that were vented to the outside. The problems that came of this design were damp, if not wet foundations and floor joists. The warm air from outside condensed on the cold pipes and foundation, creating mold, mildew and wood rot. Then winter temperatures froze the pipes and made the floor above the crawl space unbearably cold. There have been solutions designed to solve these problems, including how to heat a crawl space.

Things You'll Need

• 6 mil poly sheeting
• Staple gun
• Staples
• Insulation
• Duct tape
• Floor vents
• Fans

Instructions

1. Insulate the walls from the outside temperatures. You can install fiberglass batting with the paper side facing you along any wood framing that comes down to the concrete foundation. Do not insulate the ceiling in the crawl space as you want the heat to warm the crawl space. There is stiff insulation sheeting, XPS, that you can install over the concrete. It is excellent for this application as it is very moisture resistant and blocks the passage of air.

2. Block moisture from coming through the dirt floor. Compartmentalize your crawl space by sealing it off from the outside. Lay down 6 mil or thicker polyethylene sheeting and tape it securely along all of the sides, up and over the insulation with duct tape.

3. Provide a water drainage system, especially if the crawl space is below the outside grade. A drain around the perimeter of the floor that flows into to a sump pump hole. Keep the sump pump under the moisture barrier, taping off an access panel in the poly sheeting.

4. Start blowing in the heated air from your home into the crawl space now that it is ready for air circulation. Just make sure you have at least two air vents, one for air intake and one for air uptake. Your heated air will warm the crawl space and your floors will be warm and dry.

Tips & Warnings

• Lay sections of carpeting over the poly in areas where you might have to access plumbing or wiring Think of your crawl space as an extension of the living space in your home. If you leave it exposed to the damp soil and cut off from the conditioned air of the house, you will run into moisture problems as well as termite infestations. There must be air circulation either passive or mechanical to keep a heated crawl space. Install floor vents and fans or install ducts that can be hooked into your ventilating system. There is an excellent publication available online, listed in the Resources below.

Resources

• Heated Crawl Space
• Extruded Polystryrene Foam Association
• Chemtex - Polyethalene Sheeting