I have an unfinished attic, with cathedral ceiling, no insulation presently. in five-10years we is going to be including dormers, but Meanwhile i would want to increase insulation and drywall in the simplest, most reversible/salvageable method. My strategy is to hang two layers of 2 inch polyiso under the rafters, taped with staggered seams leaving the rafters empty, so fundamentally a vented assembly. I've extra blocking to the ground joists and can make the polyiso constant from the knee partitions. I thought I might add furring strips along with the insulation then hang drywall, believing that the furring strips would build an airgap, allowing the foil to act as a radiant barrier.
The system: Aspect A: I found one" Dow rigid foam backed five/8CDX for a similar selling price as the bare CDX, And that i intend to double it up like a SIP, setting up The underside sheet foam facet up and the next sheet on best (staggered naturally) Along with the foam going through down, providing me 2" of insulation amongst the plywood.
Your caveat is suitable and conservative. For that vast majority of builders, nevertheless, the code prerequisites will hold roofs freed from complications.
2. It sounds like you are working with metal beams to body your hips. As I am certain you know, these metal beams are thermal bridges. All insulation needs to be on the outside side on the steel.
Q. "The air barrier is to be put earlier mentioned the pine T&G ceiling and below the foam. Would you recommend that we use something that is both an air barrier along with a vapor barrier?
It is absolutely not limited to an R eighty Passive House roof. Choose out the parallel chord trusses and slender it up.
I'm opening up my property and putting in cathedral ceilings, I just preferred to verify my system since I bought next feelings looking through Increasingly more about it. My unique final decision was to go along with a vented roof procedure and R38C batts. I read a whole lot about the different methods and it nonetheless seems to me that this is the best. Livint in Atlanta GA We've to cope with both equally sizzling humid summers and cold winters, so humidity Management is a problem, This is exactly why I believe the vented approach is the best. Anyhow, I am right down to the rafters and roofdecking and furred out the existing 2x6 with 6" metal studs, so I have about eleven.5" for insulation. Mt strategy was to create a continuous air flow visit underneath the roofdeck, my dilemma goes in the direction of to implement baffles, xps board Make baffles or insect monitor nailed at furring strips to permit for that airspace.
Put in rigid foam insulation higher than the roof sheathing and air-permeable insulation concerning the rafters. Such a assembly is intended to dry to the interior, Therefore the assembly really should never incorporate an interior polyethylene vapor barrier. If you end up picking this technique, it’s doable (nevertheless not vital) to setup vent channels between the very best from the rigid foam and the best layer of roof sheathing by setting up a number of parallel 2x4s — a single higher than Each individual rafter — extending from soffit to ridge. (For more information on this strategy, see How to setup Rigid Foam Along with Roof Sheathing.)
Why not simply do it correct plus Construct with stress taken care of roof sheathing. Even regular plywood can handle wetting cycles repeatedly in excess of investigate this site our number one Tremendous low-cost OSB.
You're appropriate that this type of roof assembly won't dry to the interior. But it's not imagined to. I'd personally tape the polyiso -- the tape will never trigger any troubles.
As I spelled out within the posting on this navigate to this site web site, you can't use fluffy (air-permeable) insulation within an unvented roof assembly Except if you include rigid foam or spray foam over the fluffy insulation.
Thank you, Martin and Stephen. Fortunately we have been in a very predicament the place we will pause and reconsider, as The brand new felt is placed, but they haven't began installing shingles but. I'll examine the problem While using the contractor again. I might be able to get him to reconsider.
I have a detail for blueskin, like a both equally an air and vapour barrier, and also it can act as a seal for the screws that hold every thing down. In reference on the vaulted schematics on This website, it exhibits vapour/air barrier along with insulation, which acquired me asking yourself. As good as I'm putting in components, no one is ideal, and an air leak may possibly produce among XPS seams. As soon as ANY moisture receives down to lower sheathing, it really is activity in excess of.
Most rafters aren’t deep plenty of to accommodate the insulation required to satisfy minimum amount R-values expected by code, especially if the rafter bays consist of a ventilation channel.