If you wish to create a conditioned attic, this post lets you know what you need to know. To learn more on the topic, see Making a Conditioned Attic.
The program: Component A: I found 1" Dow rigid foam backed 5/8CDX for a similar cost as being the bare CDX, and I decide to double it up similar to a SIP, setting up The underside sheet foam aspect up and the subsequent sheet on prime (staggered of course) Using the foam dealing with down, providing me two" of insulation involving the plywood.
Builders resolve this issue by furring down or scabbing on extra framing underneath the rafters to deepen the rafter bays. A different procedure is to include a layer of cross-hatched 2x4s, 16 inches on Heart, installed beneath the rafters."
The most crucial flaw On this roof seems to be to generally be the ice and drinking water membrane at the best place within the rafter bays. Would just normal felt paper have allowed ample moisture to dissipate with the roof sheathing keeping away from rot?, I type of question it.
Cellulose insulation can keep a lot of humidity. This "moisture buffering" ability is cited by some cellulose supporters as a major gain, and certainly this capacity can in some cases avert a small dampness dilemma from resulting in a lot of rot.
That you are describing a cathedral ceiling that comes with all feasible blunders. There was no consideration to air sealing. The worst achievable insulation was made use of (fiberglass). And the roof assembly is unvented. So it truly is no shock you are seeing condensation.
Doug... For a few purpose I did't see your submit #17. Seems like two of us at the least Imagine there could be a super easy low-cost Answer.
To the roof assembly about the cathedral ceiling, does the stack-up below seize all the elements I would wish? 2x8 pine T&G (presently in position, stays since the finish ceiling)
Install a layer of closed-cell spray foam versus the underside of the roof sheathing, and fill the rest of the rafter cavity using an air-permeable insulation. All over again, this type of assembly is created to dry to the interior, And so the assembly should never ever consist of an interior polyethylene vapor barrier.
The precise design and style shown was for read review any Passive Dwelling. The roof thickness & usage of a provider cavity might look like overkill for some tasks, but If you need an airtight check here lid, a support cavity can get you there - completely... And enable you to wire and lightweight the inside.
Martin, many thanks. I just talked towards the roofer and he he has a good point turned down the idea of only Placing the foam around the family members home cathedral ceiling. That weird "jog" while in the roofline, owning it instantly bump up 4" or eight" the place the relatives home commences, in the middle of the back again facet from the roof, would defeat the idea of a constant slope for rain to come down when it hits the higher Portion of that again roof. Therefore the four" or eight" height addition desires to continue through the total next Tale roof line.
Eventually (I assure This is certainly my very last subject). About my fiberglass batts: Will the dealing with that comes with it retard the drying out procedure that I described previously mentioned (will it make a difference what aspect I put it on inside the purlin cavity?
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Ought to I treat the flat roof as a cathedral ceiling and go with spray foam (or board), fiberglass, and no humidity barrier?