Insulation, Radiant and Vapor Barriers - Ceiling-One thick or two layers?
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MacGuyr2
07-07-07, 07:40 AM
Hello Everone
This sort of ties in to the post " ceiling joist thickness same as batts" in away. I'm in the same boat with a expansion/redo of our garage to Rec Room. I saw where it was mentioned that using one layer inside the joist followed by another running perpindicular over the joist would be better.
My intent was just use R-30 16x48 Batts Faced even though the joists will be 2x8 or 2x6. So would it be better overall to use a combo of say R-19 faced inside the joists followed by R-19 unfaced crossing over the joist? I was also planning using 6mil plastic stapled on the ceiling since we're using Armstrong ceiling tiles. We're in Tennsesse and it's a four season zone for a fact. Thanks.
Kenny J
This sort of ties in to the post " ceiling joist thickness same as batts" in away. I'm in the same boat with a expansion/redo of our garage to Rec Room. I saw where it was mentioned that using one layer inside the joist followed by another running perpindicular over the joist would be better.
My intent was just use R-30 16x48 Batts Faced even though the joists will be 2x8 or 2x6. So would it be better overall to use a combo of say R-19 faced inside the joists followed by R-19 unfaced crossing over the joist? I was also planning using 6mil plastic stapled on the ceiling since we're using Armstrong ceiling tiles. We're in Tennsesse and it's a four season zone for a fact. Thanks.
Kenny J
jurched
07-13-07, 08:41 AM
Two theories on this, take your choice:
1. cris-cross, so as to prevent a "short-circuit" by the joists which would divert heat to the outside.
2. "short-circuit" does not happen with joists because the thickness of the actually does a better insulating job than the insulation itself!
J
1. cris-cross, so as to prevent a "short-circuit" by the joists which would divert heat to the outside.
2. "short-circuit" does not happen with joists because the thickness of the actually does a better insulating job than the insulation itself!
J
Concretemasonry
07-15-07, 10:17 AM
Use the appropriate insulation for the joist size.
Jamming R30 in between 2x6s or 2x8s is a waste of money. You may also get less insulation (real R-value) than the correct size insulation (R19, etc.) because of the compression of the fiberglass. If you ever get any moisture in it, plan to scrap everything since the R-value will be next to nothing.
Dick
Jamming R30 in between 2x6s or 2x8s is a waste of money. You may also get less insulation (real R-value) than the correct size insulation (R19, etc.) because of the compression of the fiberglass. If you ever get any moisture in it, plan to scrap everything since the R-value will be next to nothing.
Dick