A. It is best to only use an installation method that your insulation contractor is accustomed to. In this article inside the Northeast, several contractors would almost certainly fill your rafter bays utilizing the dense-pack system right after your new roof sheathing was put in.
Thanks - This is often new construction, I am the designer / builder, and the greater I have a look at it, I'm liking all rigid - considerably less fussy. The top layer of rigid about fluffy will make my eave far too thick anyhow. The air barrier with the T&G ceiling is in fact the sandwich of felt and taped three/8" CDX.
Q. "You say 'You don't need an interior vapor barrier,' but You furthermore may say that 'You'll need a fantastic air barrier on both sides of the fiberglass batts.' The latter would turn out to be an inside vapor barrier not so?"
Many thanks Martin - Now I see why my primary strategy for any SIPS envelope was so elegantly straightforward. It seems like min R-ten sprayed underneath the roof sheathing and then a full-fill from the bays with batt / fluffy, in addition to a vapor sealed drywall lid will get me the 'very hot' (unvented) roof system the SIPS was within the get go.
Any property currently being constructed better than the absolute minimums should really for the pretty least not use OSB for roof sheathing. Imo
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If you'd like to get it done appropriate, you have to deal with air leaks, tackle your recessed can issue, and insert enough R-price to at the very least meet up with bare minimum code prerequisites. It is many perform, but it is not rocket science. Repairing these complications could possibly be highly-priced, nevertheless.
"The common roof ventilation necessity Utilized in constructing codes and asphalt roofing suppliers calls for one sq. foot of "Internet no cost ventilation space" For each and every 300 square toes of ceiling space (attic floor location) when vents are evenly divided — fifty percent of these large within the roof on the ridge, gable, or perhaps a significant roof, and 50 % lower about the roof for the eaves.
But When the installer is conscientious, and the rafter bays really are dense-packed, my guess is that almost everything will likely be wonderful.
Lastly (I guarantee This can be my previous subject). Regarding my fiberglass batts: Will the dealing with that comes along with it retard the drying out method that I described previously mentioned (does it make any difference what facet I set it on within the purlin cavity?
We really Will not know if these roofs have good vent channels, or what sort of vent baffles (if any) ended up utilised to maintain the air flow gap concerning the highest of your fiberglass insulation and also the underside of your roof sheathing.
I must marvel In the event the failure during the Picture would've occured In the event the hip and ridge was vented and all the things else the exact same?
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That you are describing a cathedral ceiling that includes all possible errors. There was no notice to air sealing. The worst attainable insulation was utilized (fiberglass). As well as roof assembly is unvented. So it truly is no shock that you're viewing condensation.