Vapor Retarder Attic Insulation

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.

Vapor retarder attic insulation.

Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. In any case the vapor barrier must point to the warm side. Moisture moves by two transport mechanism. Liquid water can accumulate inside exterior walls and in roof and attic spaces.

That s because cellulose is the only insulation that actually manages moisture. The ability of a material to retard the diffusion of water vapor is measured in units known as perms or. Plastic vapor barriers should only be installed in vented attics in climates with more than 8 000 heating degree days. 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.

Whether or not you need a vapor retarder hinges on three main factors your climate your home and the location of the wall you re insulating. Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case. The older term vapor barrier is still used even though vapor diffusion retarder is more accurate. You can forego the plastic and use a vapor retarder kraft faced insulation or latex ceiling paint in all other climates except hot humid or hot dry climates.

This acts as a barrier to keep heated moist air from rising up into the attic during cold weather. Cima does not recommend the use of vapor barriers with cellulose insulation except in circumstances of exceptionally high moisture levels such as an indoor pool facility or very cold climates. Air movement and diffusion. This barrier is meant to keep moisture from getting to the insulation in the walls and ceilings and it is required by building codes when insulating most houses.

To know if you need a vapor retarder ask yourself a few basic questions. The kraft facing on insulation is a vapor retarder. Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers. The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.

A vapor retarder helps prevent water vapor from condensing to liquid water within the structure. In hot dry climates your attic can be vented though like in hot humid climates you should not install any vapor retarder or barrier. The best approach for a vented attic in a cold climate is installing a layer of drywall with a good coat of latex paint the paint creates a semi permeable vapor barrier. The following are a few simple steps to help you undertake the task properly so your vapor barrier retains heat without damaging the insulation.