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Spray Foam Metal Roof Question
Posted on 12/4/23 at 11:52 am
Posted on 12/4/23 at 11:52 am
Renovating an old house and will be replacing the existing galvanized corrugated metal with R panel. For cost reasons, the new metal has been installed on the wooden perlins. We're removing all of the sheathing from the house and spray foaming the exterior walls and was wondering if it is worth spray foaming the metal.
We originally intended to blow cellulose in the ceiling joists....but i've read where the metal may sweat if not spray foamed...so now contemplating spraying with open cell foam.
Looking for opinions.....
TIA
We originally intended to blow cellulose in the ceiling joists....but i've read where the metal may sweat if not spray foamed...so now contemplating spraying with open cell foam.
Looking for opinions.....
TIA
4
Posted on 12/4/23 at 2:30 pm to failuretocommunicate
On our barndo build we wound up with open cell throughout. The roof and gable ends were PBR panel over metal purlins, walls were 2x6 studs/osb/felt/PBR
Run conduit to breaker panel and to any future work now. There's always a circuit or two that you wish you'd added.
Closed cell would be your vapor barrier and better R in a 2x4 wall.
Run conduit to breaker panel and to any future work now. There's always a circuit or two that you wish you'd added.
Closed cell would be your vapor barrier and better R in a 2x4 wall.
Posted on 12/5/23 at 6:54 am to failuretocommunicate
I always have a hard time with the mental hurdle on how exactly would I track down the location of roof leak if I sprayed foam on the underside of that R panel. Yeah I know apply the R Panel correctly and that won’t happen but the thought of tearing off sections of foam to locate a leak just is not a pleasant thought. I guess that’s just the old man in me.
Posted on 12/6/23 at 9:39 pm to failuretocommunicate
Make sure you have proper ventilation, both soffit and attic
My main concern would be the bushings on each screw. With the roof insulated underneath, the heat would have a hard time transferring down to the attic and then expelling through the vent. You may find the bushings wear out a little quicker than normal because of the lack of heat transfer. Remember, when you take the screws out, you have to jump up one size in diameter to ensure a proper seal and structural integrity. Just something to keep in mind
My main concern would be the bushings on each screw. With the roof insulated underneath, the heat would have a hard time transferring down to the attic and then expelling through the vent. You may find the bushings wear out a little quicker than normal because of the lack of heat transfer. Remember, when you take the screws out, you have to jump up one size in diameter to ensure a proper seal and structural integrity. Just something to keep in mind
Posted on 12/7/23 at 2:28 pm to failuretocommunicate
After Ida, I sprayed my entire camp with closed cell. Walls, ceilings, floors, everything. Now it is a mobile home and so there is a lack of attic space, but we have not ran into any issues with it being against the sheathing under the tin roof. Its basically a sealed ice chest. The AC cycles better than it did pre Ida and it def feels cooler in the summer with no issues of condensation.
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