Omitting a ceiling vapor barrier by arguing that you have to let the moisture escape or because the house has to breathe out the top is actually correct in a way.
Vapor barrier in garage ceiling.
If you re adding new garage doors be sure to install insulated options.
A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.
So you don t need a vapor barrier in the garage ceiling.
Thus installing vapor barriers on wall surfaces must.
The science of moisture movement.
It s also incorrect in a way.
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.
After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.
First of all a garage is not a signicant source of vapor as it is not occupied that much and you don t cook or bath in in it.
And the ceiling acts as a enough of a vapor retarder.
Now i m a real fan ha ha of controlled mechanical ventilation to limit interior moisture levels in cold and mixed climates as well as to.
Install as directed typically cutting to fit and using a staple gun to attach the vapor barrier to the studs.