I own a pre-fab ranch home built in the 40’s. The roof and ceiling cross members are 2×4 trusts. The attic insulation is completely destroyed due to age and the paper vapor barrier is brittle and has crumbled. I am currently cleaning all of this out. But I am not sure what to use as a vapor barrier. My concern is how can a get a good vapor seal between the living space and the attic. Also should I use a 6″ insulation bat or a 4″ bat with a 4″ cross bat (no vapor backing)? Thanks, John.
Replies
Don't think in terms of vapour barrier because it's the most abused term in construction.
Think in terms of air barrier.
Insulate with the best you can afford and cover the ceiling as evenly and completely as possible.
Take a can of spray foam insulation and seal every outlet in the house. Get that nozzle between the drywall and the electrical boxes and fill till it overflows.
Remove the window casings, door casings and baseboards.
Fill all the gaps as well and then re-install the casings and baseboards.
Attack the gaps as if you were trying to protect your family from killer ants.
A new coat of latex paint will serve as a vapour barrier when your done.
Gabe
Have to agree with Gabe. You never really had a vp with the kraft faced insulation in the first place, why worry about one now? Since you are just doing the attic area , after you clean out the old insulation, do a thorough air sealing of all wall and ceiling penetration as mentioned. Use a minimally expandind foam, and a "fire stop" type caulking. Blow in a cellulose insulation if possible, it will give you the most R value per inch of insulation, and is itself a decent draft stopper. If you go back with fiberglass batts, used the unfaced. Run one layer in your joist bays, and second layed across the bays. F/G should also be carefully fit around wiring and other obstructions to be effective.
Dave