Insulation against under side of Roof Deck
In an effort to reduce temperature difference between the attic and living space I was thinking of installing baffles on the under side of the decking and installing R-30 (Kraft Faced facing towards attic)between 2×10 rafters. Baffles would extend from eve to ridge, much like a cathedral ceiling . Any concerns, moisture issues with this idea? Will cool roof decking lead to condensation/wet batts in winter? Home details Standing seam metal roof (12 on 12 pitch) ~400 sq ft of Room in attic, could be finished as living space Located in Central NC decking material- 3/4″ tung and groove pine attic venting is through vents in eves Air handler for unstairs is located in attic I have more than enough R-30 fiberglass already purchased to do the job.
Replies
Why do you want to insulate the attic? Would make more sense to add the insulation to the ceiling.
attic venting is through vents in eves
What about ridge venting, or other rooftop venting? You need more venting than just at the eaves.
HVAC + duct work in attic. Want to lower the temp difference between living space and attic. Lower temp difference = less heat transfer. Can't add more insulation to ceiling below. I've install 3/4 plywood flooring in attic over top of 2x10 ceiling joist.
My main concern is moisture. Warm moist air migrating through the insulation & baffle coming in contact with cool roof deck <45 reply
If there are baffles... the insulation isn't against the roof deck... right?
correct......
The thread title is confusing--you're not putting insulation against underside of roof deck. Anyway, assuming you have venting at eaves and ridge and baffles all the way, your installation is totally standard. Faced fiberglass batts that are overlapped and stapled to the rafters are reasonably effective as a vapor retarder, and I would not expect problems unless humidity in the attic is high and the roof decking is cold... how high and how cold are region-specific and you need to understand what's commonly done and what commonly results in your area. In most finished spaces you'll also have drywall on the underside of the rafters, and if this is made reasonably airtight you should be fine.
He hasn't stated (that I know
He hasn't stated (that I know of) that he has venting a the ridge.
He stated that he does not. He should add it.