Your strategy will get the job done fantastic, so long as the layer of rigid foam along with your roof sheathing has an R-value of a minimum of R-20. If you're utilizing XPS, you may need a minimum of 4 inches of foam. When you are using polyisocyanurate, you'll need not less than three inches of foam.
When you go forward together with your program, it is best to consist of a smart vapor retarder on the inside aspect with the assembly, to minimize the transport of humidity from the interior to your sheathing.
Also, wouldn't the internet site-created plywood baffles among the rafters provide the very same difficulty; sluggish drying by means of diffusion? ( I suppose I could use fiberboard for baffles)
When your weather will not be much too serious It truly is probably all right to obtain just the R-ten foam around the structural steel, Though you will find some threat that the metal could sweat in cold climate. I am assuming you also meant to insulate the 2x12 joist bays to Obtain your whole R-benefit to a reasonable level.
This can be an alternative I'm contemplating in my residence to avoid wasting the past house owners freshly put in roof shingles, though the depth with the rafters are not able to accomodate sufficient insulation to fulfill code. I'm wondering if I need to furr out the rafters to acquire the desired thickness of spray foam, or if putting in a number of inches of polyiso foam to the underside in the rafters, following the spray foam, could do the job?
Almost all of the information I run across is apparently from the cellulose business that claims wind-clean is an enormous dilemma with fiberglass; and through the fiberglass marketplace which asserts the cellulose team overstates the issue and that towards the extent wind-clean takes place it is absolutely inconsequential.
You wrote, "the Full Report rafters remain exposed," but I'm not sure Whatever you necessarily mean by that. Do you have got kraft-confronted batts in between the rafters, Along with the kraft facing however seen?
Modifying the Intelo membrane to glued & taped OSB or Plywood which has a support cavity down below product of framing lumber does make the assembly easier to develop.
I now know that stucco cannot be placed on a roof, so I'll revert towards the a steel roof, but nevertheless want to get an unvented attic. I have examine by means of "Developing a conditioned attic", and am still not Related Site sure as to helpful resources The ultimate way to commence.
The most beneficial solution is to do all the work simultaneously: rigid foam above the roof sheathing (as encouraged while in the write-up), and fluffy insulation beneath.
I'm sorry to become the bearer of poor information, nevertheless the sections of roof which might be insulated with six inches of fiberglass and inside polyethylene weren't insulated correctly. In Those people sections, the roof sheathing is prone to humidity accumulation and rot.
An additional situation that arrives up in that state of affairs is whether or not that may endorse condensation to the underside from the one" XPS when it truly is chilly more than enough outside the house as the underside with the XPS may very well be beneath the dew point? Q-3: What to do after we re-roof.
[Editor's note: Monthly bill Rose just sent me the next responses in an e-mail; he bundled his permission to article the responses.]
Q. "Are you declaring that escalating ventilation to that second Tale attic would basically be a bad idea, if we go on the foam above the entire second story gable roof, and as a substitute we must always enable it to be totally unvented?"