Do I Need Vapor Barrier In Garage Ceiling

So poly the walls and ceiling and seal everything up well.

Do i need vapor barrier in garage ceiling.

There s one other important qualification. You can see a couple pictures of the garage and rafters here. Without making sure of these components you could end up with a mold and mildew mess. Where the poly meets the spray foam at a.

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. So you don t need a vapor barrier in the garage ceiling. Not every wall does. 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.

Hence the need to reduce moisture flow into the attic and the need for a vapor barrier. And again do i need a vapor barrier. This is normally done because it s the most cost effective method to achieve the desired level of comfort and ease of installation. Whether or not you need a vapor retarder hinges on three main factors.

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. Unless you have converted your garage into a kitchen a bathroom a laundry room or a space that generates a lot of moisture even for that a dehumidifier can absorb all the moisture in the garage to keep the air dry. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. Vapor moves in two ways by diffusion through materials and by air leakage through gaps and holes in building assemblies.

Understand that this is a climate specific recommendation. 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. Installing the vapour barrier in this type of insulated garage is a little different then normal. There should be a continuous ridge and soffit ventilation.

This will help to exhaust the water vapor that will collect. And the ceiling acts as a enough of a vapor retarder. Between the two air leakage moves far more moisture than vapor diffusion. A vented attic in a moderately cold climate or mixed climate.