Vapor Barrier Attic Floor

Below grade walls and floor slabs transmit ground moisture through concrete walls or slabs.

Vapor barrier attic floor.

A plastic vapor barrier is best installed in a vented attic within climates with over 8 000 heating degree days. Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers. Most forms of attic insulation benefit from the addition of a vapor barrier to protect them from the harmful effects of moisture which can reduce their effectiveness over time. Plastic vapor barriers should only be installed in vented attics in climates with more than 8 000 heating degree days.

Crawl spaces benefit from a polyethylene moisture barrier placed directly over the exposed earth. Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case. Because it s nearly impossible to seal penetrations in the ceiling the reality is water vapor will get into the attic. This acts as a barrier to keep heated moist air from rising up into the attic during cold weather.

A vapor barrier against the concrete surface is generally recommended before wood framing or flooring materials are installed. The following are a few simple steps to help you undertake the task properly so your vapor barrier retains heat without damaging the insulation. If your climate does not meet these conditions a vapor retarder like latex ceiling paint will work well for your house if you are in all other climates except the hot dry and hot humid.