Ideally, you want to have an airtight barrier previously mentioned and underneath your fiberglass batts. If you're able to accomplish Individuals two air limitations, then wind-washing is just not an issue inside of a roof like yours. (It could be inside a vented unconditioned attic, naturally, In particular near the soffits.)
Thanks, Martin and Stephen. The good news is we're within a circumstance where we will pause and rethink, as The brand new felt has become placed, but they haven't started off installing shingles nevertheless. I will go over the problem Using the contractor again. I might be able to get him to reconsider.
I'd increase to Martin's list of components for rafter vent channnels, fiberboard sheathing. I take advantage of I joists for vented cathedral ceilings and staple 1/2" fiberboard to The underside of the top twine of your I joists. It could be ripped over a desk observed and installs rapidly, fiberboard does have a high perm score and should allow smaller quantities of dampness to pass through in to the vent Room.
Many thanks Martin - Now I see why my unique strategy for your SIPS envelope was so elegantly straightforward. It seems like min R-10 sprayed beneath the roof sheathing and then a full-fill in the bays with batt / fluffy, in addition to a vapor sealed drywall lid will get me the 'warm' (unvented) roof technique the SIPS was with the get go.
I now understand that stucco cannot be applied to a roof, so I will revert to your a steel roof, but nonetheless want to possess an unvented attic. I have read by "Creating a conditioned attic", and am even now undecided concerning The obvious way to move forward.
Martin, re: altering the attic above the 2nd Tale bedrooms to the conditioned attic and sealing the soffit vents.... Before this most up-to-date concept about insulating with rigid foam along with the cathedral ceiling, we were planning to Lower a ridge vent into your gable ridge, so as to meet ventilation code requirements. At this time We have now eave vents in addition two relatively worthless gable vents, 1 on either side.
If you wish to Blend air-permeable and air-impermeable insulation, There's two achievable methods to commence. A person alternative (according to the code) calls for: “Together with the air-permeable insulation installed right beneath the structural sheathing, rigid board or sheet insulation shall be set up right previously mentioned the structural roof sheathing as specified in Table R806.five for condensation Management.â€
I suspect that Bill Rose is true: most of these failures involve dampness that is definitely carried by relocating air. They are not diffusion failures. If your rafter bays seriously are appropriately dense-packed -- an enormous if -- the possibility of air movement is extremely small.
When your weather is not really far too severe It is really in all probability ok to get just websites the R-10 foam more than the structural steel, although you can find some risk that the steel could sweat in cold weather. I am assuming Additionally you meant to insulate the 2x12 joist bays to Get the total R-price to an inexpensive level.
When you are thinking of shifting to a number of places or perhaps inquisitive about diverse parts of the nation, you ought to take a look at multiple cities.
I have a mansard roof with steep sides with gables, and an almost flat top rated which has a rubber roof. There are no vents, it hasn't been insulated before I started engaged on it and also have two questions:
I'm with Martin on this 1, your element is labor intensive for small if any obtain in my opinion. The vent channels we explain can be achieved once the roof is on from the underside (dry aspect). For the people of us constructing in a cold weather this can be a large advantage, we shell out as tiny time as is necessary to the roof.
I have a partial cathedral ceiling within the concluded attic of my household in zone 4 (TN). Each and every slope from the roof is split around in thirds by 3 distinctive scenarios: knee walls for the outer thirds, "cathedral" ceiling in the middle thirds, plus a vented "attic" in the center 3rd that has a ridge vent - a typical situation with completed attics, not less than all over in this article. I've a huge issue in the summertime with overheating. The insulation is not Doing the job perfectly mainly because it was poorly insulated with just R-19 fiberglass batts amongst the rafters without having a ventilation baffle or ample soffit venting and only r-19 blown into the "attic Place". What's more, my upstairs HVAC ducts investigate this site are run within the genuinely incredibly hot "attic" Place under the ridge. Depending on what i haved figured out from various posts in this article, my prepared Answer would be to cathedralize your complete roof, eave to ridge: put in continous air-restricted web page-designed two" vent channels using foil-confronted polyiso board (as suggested in ), setting up continual soffit vents to significantly improve the airflow from soffit to ridge, generating an air-restricted ceiling under the rafters, and, most significantly, provide the ductwork Within the conditioned envelope.
Builders address this issue by furring down or scabbing on supplemental framing down below the rafters to deepen the rafter bays.