Raised Home & Under-Floor Insulation in Galveston, TX

Raised home and under-floor insulation is one of the most common needs on Galveston Island, Tiki Island, Jamaica Beach and the Bolivar Peninsula. Homes there are lifted on pilings or piers, and their floors sit over open air rather than a slab or a closed crawl space. Wind blows across the underside of the floor, salt air reaches the framing and humidity stays high most of the year.

Why batts fail under raised floors

Fiberglass batts held up with wire or netting are the traditional choice, but under a raised floor they sag, collect moisture, blow loose and give pests a place to nest. Once they drop away from the subfloor, they do very little. Many homeowners find their floor insulation lying on the ground after a few years or after a storm.

Closed-cell foam under the floor

Closed-cell spray foam sprayed against the underside of the subfloor, between the joists, sticks to the wood, seals the gaps at the edges and plumbing penetrations and does not absorb water. That keeps the floor warmer in winter cold snaps and cooler and drier in summer, and it cuts the humid air that leaks up into the house. The Department of Energy suggests R-13 for an uninsulated floor in Zone 2, which closed-cell foam reaches in about two to three inches.

Protecting the foam

Under raised homes the foam may need a covering, depending on how the space below is used and what local rules require. Areas below base flood elevation generally must use flood-resistant materials and can only be used for parking, access and limited storage. We discuss what the space below your home is used for and how to protect the insulation.

Pier-and-beam and crawl space homes

On the mainland, older pier-and-beam homes with a short crawl space have similar issues. Closed-cell foam under the floor, or sealing and insulating the crawl space walls with a vapor barrier where the space can be closed, are both options.