Any home currently being built a lot better than absolutely the minimums ought to within the incredibly least not use OSB for roof sheathing. Imo
If you would like create an unvented insulated roof assembly, you've two possibilities: (a) You are able to increase rigid foam to the exterior aspect within your roof sheathing, accompanied by a 2nd layer of roof sheathing and new roofing, or (b) You'll be able to insulate the underside of the roof sheathing with spray polyurethane foam.
U.S. building codes never involve the usage of inside vapor boundaries, even in cold climates. What they do require is undoubtedly an inside vapor retarder. This prerequisite can be satisfied with kraft experiencing on fiberglass batts or vapor-retarder paint.
Thanks - This really is new development, I'm the designer / builder, and the more I examine it, I'm liking all rigid - a lot less fussy. The best layer of rigid over fluffy helps make my eave much too thick anyways. The air barrier to the T&G ceiling is really the sandwich of felt and taped three/eight" CDX.
By Martin Holladay
It can be certainly not limited to an R eighty Passive Dwelling roof. Get out the parallel chord trusses and slender it up.
Your program to setup eight inches of rigid foam is a superb a person, however you may be able to install thinner foam if there is a powerful purpose to take action. Of course, eight inches of rigid foam has a higher R-worth, and can accomplish improved, than a thinner layer.
I have many partitions to re-insulate, and after the roof is handled I will have rafter bays to insulate, and It will be valuable to get some Perception into which sort of fiberglass will give you what profit for its Value.
The perimeters of the roof are included with asphalt shingled (GAF Slateline to be correct). It appears like I really should pull down the fiberglass and possess it spray-foamed prior to I drywall.
We wish to insert keep track of lights to the new ceiling, with its electrical provide running in the new cavity produced with the insulation. The present lover also demands its electrical source to run as a result of that House.
If you need to opt for a cloth that is a little bit extra vapor-permeable for your ventilation baffle, you are able to -- for instance, some individuals use slender plywood or fiberboard in this locale -- but Homepage you truly do not have to. The EPS will function
Sorry, Martin, I now realize that "new construction" would not always mean "new residence being designed", and "an unvented attic, with R-fifty under the roof" ought to have been "an unvented attic, with an R-fifty roof'. Simply because It really is clear to me does not imply It can be crystal clear to All people else.
I have a issue for blueskin, for a both equally an air and vapour barrier, and also it will eventually work as a seal for the screws that keep all the things down. In reference for the vaulted schematics on This website, it shows vapour/air barrier on top of insulation, which obtained me asking yourself. Pretty much as good as I am putting in products, no person is perfect, and an air leak could develop concerning additional resources XPS seams. Once ANY dampness receives all the way down to lower sheathing, it really is video game more than.
Most rafters aren’t deep sufficient to accommodate the insulation required to satisfy minimum amount R-values expected by code, particularly when the rafter bays include things like a air flow channel.