Whether or not you need a vapor retarder hinges on three main factors your climate your home and the location of the wall you re insulating.
Vapor barrier roof rafters.
I have a 1961 single story home with a cement floor crawl space.
4 times the cost of fiberglass batts.
Vapor barrier on under side of floor joists over a crawl space oct 26 2011 alex in seattle said.
You could insulate the roof the traditional way.
Whether or not you use vapor retarder you want an air tight air barrier such as well sealed drywall to keep out moisture from the house.
Hopefully you have installed a vapor barrier between the roof purlins and the roof steel.
To know if you need a vapor retarder ask yourself a few basic questions.
Its closed cell structure stops water vapor and the foil covered face acts as a radiant barrier.
White bubble between roof and rafters.
Attic vapor barrier detail for cold climates the best approach for a vented attic in a cold climate is installing a layer of drywall with a good coat of latex paint the paint creates a semi permeable vapor barrier.
Most authorities now agree that vapor barriers are important under certain conditions but not necessarily as a whole house solution for every home.
That reduction of air and moisture infiltration can then help improve roof longevity.
Not recommended for exterior below grade applications.
A roof design that includes an adhered roof membrane with multiple layers of insulation with board joints offset and staggered over a vapor retarder air barrier helps lower the risk that air and the moisture it carries will infiltrate the roof system.
Resolution of the vapor barrier debate.
We have some moisture issues that i will address at a later time but i d like to install a vapor barrier on the underside of the 1st floor subfloor as well as insulation.
From what i ve read online it seems wise to install a vapor barrier over the plywood to prevent condensation from getting absorbed into the plywood from the steel roof.
Rosemary june 5 2015 at 3 03 pm.
My question is should iuse a vapor barrier inthe attic floor.
But it seems the.
Not flammable but it must be protected with wallboard.
No wrap on walls.
A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.
The previous owner has 1 foam insulation with a a plastic vapor barrier only on the rafters of the roof about4 from the slate roof but not on the walls of the attic.
There are certainly other options.
That is create a vent channel above the insulation with low and high vents.
The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.
Plan is to after foam put barrier and steel panel up and then.
