Does Blown In Cellulose Insulation Need A Vapor Barrier

Are getting energy audits with recommendations to blow in cellulose into the empty exterior wall cavities.

Does blown in cellulose insulation need a vapor barrier.

Of course it s important to always check as some local building codes may still require an air barrier or vapor barrier be installed. Your first job after the studs are in place is to fill those walls with insulation. Thousands of houses. Homes and buildings located in a colder northern climates of the continental u s.

After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. Hygroscopic means a substance tends to absorb moisture from air it manages moisture as well. Air movement and diffusion. Cellulose insulation has an average thermal value of r 3 7 so you d need just over five inches to equal an r 19 batt.

Likely do not need an air vapor barrier where cellulose insulation is used. In summary we do not recommend the use of vapor barriers with cellulose insulation except in circumstances of exceptionally high moisture levels such as an indoor pool facility and we warrant our cellulose insulation for the life of the building when installed by an approved greenfiber insulation contractor. It does an excellent job of limiting air movement and because it is hygroscopic definition. If you are not sure if you need insulation in your walls follow along with this flow chart.

Moisture moves by two transport mechanism. Vapor barrier is always installed on a warm side of the house in a winter with a fiberglass insulation but cellulose manufacturer doesn not recomend installing vapor barrier with this type of insulation. 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. A bag of cellulose runs about 11 50 and will cover 36 7 square feet at a.

A lot of us with older 100 years homes are getting energy audits with recommendations to blow in cellulose into the empty exterior wall cavities. I have read that without a vapor barrier. Air sealing an attic. Without a vapor barrier show faster drying and lower overall moisture levels over identical assemblies with vapor barriers installed.

Not every wall does. That s because cellulose is the only insulation that actually manages moisture. If you decide to go ahead with the plan to install cellulose on the attic floor you don t need a vapor barrier. According to fallow we are not sure we agree cellulose insulation requires no vapor barrier in the overwhelming majority of installations.