After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one.
Vapor barrier in garage or not.
Vapor barriers are not typically intended to retard the migration of air.
Most garages don t need vapor barriers because the amount of vapor that diffuses through garage walls ceilings and the floor is not enough to cause wet walls that result in moisture damages.
Most authorities now agree that vapor barriers are important under certain conditions but not necessarily as a whole house solution for every home.
I install my vapor barrier in the middle of the wall system between the two walls.
A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.
Some debate still occurs over how necessary vapor barriers are but a consensus is growing closer.
In circumstances where conditions inside a home or office are much different than outdoor conditions water.
Such a location works both as a vapor barrier as well as an air barrier and eliminates the need for an external air barrier not a easy application on a multi storried building as well as any special electrical pans and their sealing.
Resolution of the vapor barrier debate.
And the ceiling acts as a enough of a vapor retarder.
However if you live in a cold climate zone such as alaska it s a good idea to install a vapor barrier on the warm in winter side of the wall.
You can forego the plastic and use a vapor retarder kraft faced insulation or latex ceiling paint in all other climates except hot humid or hot dry climates.
Confusion on the issue of vapor barriers and air barriers is common.
That is the function of air barriers.
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.
The confusion arises because air often holds a great deal of moisture in the vapor form.
In hot humid climates attics should not be vented and vapor.
When this air moves from location to location due to an air pressure.
Not to mention that closed cell spray foam gives us a barrier between the carbon monoxide and the inside of the home.