Installing Foam Board Insulation Over Fiberglass Batts In A Floor

Blown in or loose fill insulation.

Installing foam board insulation over fiberglass batts in a floor. For example insulating a 10 square foot wall area to r 15 costs about 3 40 to 4 00 with fiberglass insulation while a comparable r value for rigid foam costs roughly 10. I thought there was insulation in that 8 25 space but there isn t. This type of insulation typically fiberglass or cellulose insulation can be added over existing insulation provided it s installed. The fiberglass batts in the wall above it extend past the bottom of the wall cavity and fit loosely into the cavity of the 2 12 floor joists hiding the fact that there is no insulation in that void.

Rigid foam insulation offers a thermal resistance between r 5 and r 8 roughly twice that offered by traditional batt insulation. Roll or batt insulation. Fiberglass batts compressed bottom photo pretty much any crawl space with fiberglass batts in the floor above will have the first problem. Here are the installation methods from lowest to highest average r value per inch.

In general the insulation s method of installation can give you an idea of how it compares to other types of insulation. Learn more about spray foam. Do not install insulation with a vapor barrier or facing on top of any other insulation because doing so causes condensation moisture in an area that should remain dry. Foam board insulation is easy to use and is a great diy way to add some insulation.

Spray foam can be used almost anywhere in the home including exterior walls ceilings floors attics and basements. It comes in standard size 4 8 sheets and smaller sizes in many different thicknesses from 1 4 inch to 2 inches. Install these panels over wall or ceiling cavities including those filled with existing fiberglass batts to boost the r value and improve home comfort and efficiency. Though some batts come with a paper or foil facing that can act as a vapor barrier tom silva prefers to use 6 mil polyethylene sheeting cut to fit between the joists and with seams sealed by foil tape to prevent moisture from seeping into insulation.

It may not happen right away but gravity is patient. Fiberglass insulation is less than half the price of rigid foam insulation when calculated by r value per square foot. Whether using loose fill or batts put the vapor barrier closest to the warm side of your. It is made from fiberglass strands that create a barrier for air flow.

Even though it s the weakest of the three fundamental forces of nature it s plenty strong enough to pull those batts down over time. Batt insulation is that pink fiberglass found in exterior walls attic floors and the crawlspace ceiling.