Lower-and-cobble is definitely an insulation system employed by some homeowners, but under no circumstances by insulation contractors. It requires reducing rigid insulation into narrow rectangles, and inserting the rectangles involving rafters or studs.
My home built in sixty three below in Ohio provides a cathedral ceiling without air flow. In truth there quite a few cross-supports jogging perpendicular to the main joists together with other framing aspects that will make this unfeasible. So I want to make it a successful unvented roof. Fifty percent in the roof has 2x8 joists and the opposite half has 2x12s. Today There's a membrane covering (rubber) that's worked nicely for over twenty years but is exhibiting indications of deterioration and may possibly need to have changing quickly. Having accomplished reworking on the inside and strolling on the roof I understand that many the sheeting must get replaced together with the little insulation that is there now. We've had condensation difficulties up to now so I now you can find air infiltration and bridging challenges.
I obtained a disaster of the dwelling which was partially remodeled, It truly is in Zone sixteen (a California designation just like IRC zones). It's a 6/twelve vaulted ceiling above the residing/kitchen spot. The roof is held up by two long beams that run four toes out parallel to your ridge , Therefore there isn't any straight air path a the way up to the peak ridge beam.
A. As I wrote in the posting, "Most rafters aren’t deep sufficient to accommodate the insulation necessary to satisfy minimal R-values needed by code, particularly if the rafter bays consist of a air flow channel. ...
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Many thanks for that affirmation and tips. Considering that all the things is dry this time of yr and the home was lately tented for termites, I'll insulate with the beam and seal up the apparent air entryways. When I am able to see within I do think I'll have a greater idea how much humidity has been in there over the years.
It's a code violation to put in an air-permeable insulation like fiberglass batts amongst unvented rafters. It's also a bad concept, simply because dampness can accumulate on your roof sheathing if you try this method, and you may end up having sheathing rot.
Am i able to get some extra commentary over the "whole roof" of Ice & H2o Shield? I believe this had very little to perform Using the failure. The explanation why I check with is I have an identical "whole roof" design and style coming up, Nonetheless, the rafter bays are all straight operates with soffit vents, constant vent baffles (1/2" plywood) and continuous ridge vent. Dense pack cellulose, two" XPS down below 2x10's, air limited drywall (XPS could possibly be sealed up also).
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Install closed-cell spray foam from the underside of the roof sheathing, and no other sort of insulation. Make certain that the thickness in the spray foam is ample to fulfill minimal code necessities. Remember that open-cell spray foam is risky in all local climate zones, and if open-cell spray foam is set up Within this place in a chilly local climate, the underside with the cured foam have to be coated with gypsum drywall which has been painted with vapor-retarder paint. Vapor-retarder paint is ineffective if it is sprayed immediately on the cured foam.
You wrote, "the rafters are still uncovered," but I'm undecided Whatever you necessarily mean by that. Do you have kraft-confronted batts amongst the rafters, With all the kraft going through still obvious?
I have an unfinished attic, with cathedral ceiling, no insulation presently. in five-10years we are going to be including dormers, but Meanwhile i would like to insert insulation and drywall in The best, most reversible/salvageable way. My approach is to hang 2 layers of 2 inch polyiso under the rafters, taped with staggered seams leaving the rafters vacant, so primarily a vented assembly. I've added blocking to the ground joists and is likely to make the polyiso continuous from the knee partitions. I thought I might insert furring strips along with the insulation then dangle drywall, believing that the furring strips would create an airgap, letting the foil to act as a radiant barrier.
four. After getting R-twenty or R-twenty five of rigid foam site link in addition to your sheathing, it is possible to securely insulate under your sheathing with Nearly any sort of insulation you pop over here ought to use to deliver your insulation approximately minimum code demands.
You say "You don't want an interior vapor barrier," but In addition, you say that "You will need a superior air barrier on either side within your fiberglass batts." The latter would grow to be an inside vapor barrier not so?