How Do I Insulate My Crawl Space?

Frosty weather will be here soon and, if your home has a crawl space, chances are the floors above will be cold. Follow these important DOs and DON’Ts to keep the floors warm and your feet cozy.

DO permanently close crawl space vents. When vents are left open, outside air moves freely into the crawl space, hangs beneath the floors, and seeps into the living areas above. Our gasket-sealed CleanSpace vent covers are the perfect solution to stop unwanted outside air from entering your crawl space. 

DON’T put insulation between the floor joists. Instead, it should be installed against the air boundary surfaces, which are the crawl space floors and walls. The goal of insulation in a crawl space should be to make it part of your home’s conditioned space by sealing it from the cold outside air. Think of it this way: Would your home stay warmer if you insulated the interior walls between rooms? Of course not! Instead, the insulation is applied to the outside walls and in the attic (your home’s above-ground air boundaries).

DO insulate the rim joist. We recommend expandable spray foam to seal the small spaces between the sill plate and the top of the foundation. Be sure to seal other common sources of air leaks like spaces around wires or pipes and holes going into the garage.

DON’T use fiberglass insulation, which is loose and allows air to pass right through it. Plus, when it gets just a little damp, it loses any insulating value – and crawl spaces tend to be full of humidity. Instead, we use our exclusive SilverGlo wall insulation, which has a shiny silver surface that acts as a radiant barrier and reflects heat back into the crawl space. We also offer TerraBlock, a durable, long-lasting insulation made specifically for crawl space floors. It’s perfect for blocking the cold coming up from the ground.

DO keep your crawl space dry. Water and humidity are the enemies of a healthy crawl space. Even if there’s no visible water, humidity from the ground creates water vapor. That vapor clings to organic materials like wood floor joists (and the paper backing on fiberglass insulation) and makes an ideal environment for mold to grow. Encapsulation with our exclusive CleanSpace vapor barrier, along with the SmartSump sump pump system and a SaniDry Sedona dehumidifier, is the best way to tackle crawl space water and humidity. A dry, encapsulated crawl space also stays much warmer.