Do I Need Vapor Barrier In Garage Ceiling

The space that will become the attic is vented via wall vents under the peak of the roof on both sides of the garage.

Do i need vapor barrier in garage ceiling.

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. Not every wall does. Where the poly meets the spray foam at a. So you don t need a vapor barrier in the garage ceiling.

And the ceiling acts as a enough of a vapor retarder. There s one other important qualification. Hence the need to reduce moisture flow into the attic and the need for a vapor barrier. Installing the vapour barrier in this type of insulated garage is a little different then normal.

And again do i need a vapor barrier. You can see a couple pictures of the garage and rafters here. Vapor moves in two ways by diffusion through materials and by air leakage through gaps and holes in building assemblies. This is normally done because it s the most cost effective method to achieve the desired level of comfort and ease of installation.

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. Whether or not you need a vapor retarder hinges on three main factors. A vented attic in a moderately cold climate or mixed climate. If you are going the extra mile to insulate your garage ceiling try to stay away from faced insulation.

Between the two air leakage moves far more moisture than vapor diffusion. This will help to exhaust the water vapor that will collect. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. Understand that this is a climate specific recommendation.

So poly the walls and ceiling and seal everything up well. The traditional way to insulate the walls and ceiling of a typical garage is to install fibreglass batt insulation in the walls and attic space followed by a six mil poly air vapour barrier and drywall. Having said that i do not have a problem with relieving some of the moisture load in the house via diffusion hence a vapor retarder in a ceiling rather than a vapor barrier through a roof assembly that can handle it i e. Because you do not want to add a vapour barrier over the spray foamed area all you need to do is install one in the area that you did yourself.