Vapor Transmission Through Ceiling To Attic

The attic floor which is the ceiling of the living space below often already is insulated.

Vapor transmission through ceiling to attic.

Multiply by the appropriate factor from table 1 below to learn the total gross vent area needed. In the old days in severely cold climates where attics were poorly insulated it was okay to omit a plastic ceiling vapor barrier. The science of moisture movement. Lastly i am curious about the recommendation on your blog to reverse the ceiling fans to decrease the radiant heat transmitted from the attic through the ceiling.

Water vapor can pass through building materials in several ways including direct transmission and by heat transfer but studies suggest that fully 98 percent of the moisture transfer through walls occurs through air gaps including cracks around electrical fixtures and outlets and gaps along baseboards. So compared to that hot humid attic the vapor pressure at the other side of the foam is a factor of six higher. Thanks for some very informative posts by all. Thus installing vapor barriers on wall surfaces must.

Standard batts and high performance batts can be used under floors. Divide this number by either 150 no vapor retarder or by 300 vapor retarder in place. Determine where vents will be located. When insulating floors over unheated basements or crawl spaces faced products should be used and vapor retarders should face heated areas and be in.

For instance the building code s ratio of one square foot of open ventilation area to 300 square feet of attic square footage assumes a vapor barrier is installed between the ceiling and the attic space to retard the migration of moisture vapor into the attic. Insulation and exit the attic through the roof vents. The heat loss from the house warmed the attic sufficiently to allow attic ventilation to remove moisture from the attic. If it is and you plan to provide heating and cooling to the finished attic space you need to remove.

Floor insulation can also help with sound transmission so it can make sense to use it even between two conditioned spaces. That is a new one on me. Cathedral flat and hip roof ceilings with vapor retarders need a vent area of 1 sq.