I do not are convinced the burden of plywood or OSB will likely be a problem, but In case you are worried about the extra pounds, it is possible to usually seek advice from an engineer.
I'm accustomed to that approach and possess utilised it on previous double walls with flat ceiling/ truss roof assemblies. Labored wonderfully.
If you need to make an unvented insulated roof assembly, you almost certainly don't desire to disturb the tile roofing. Meaning that one of the most suitable insulation can be spray polyurethane foam. Certainly, the present insulation ought to be taken out right before you put in the spray foam.
If you wish to set up a combination of shut-mobile spray-foam within the underside on the roof sheathing and air-permeable insulation involving your rafters — an approach often identified as “flash and batt†— the developing code demands that spray foam (or, arguably, rigid foam insulation) be “applied in direct contact with the underside in the structural roof sheathing†and the foam insulation satisfy the necessities “laid out in Table R806.
This is often an option I'm taking into consideration in my residence to save the earlier proprietors recently installed roof shingles, however the depth in the rafters are not able to accomodate ample insulation to satisfy code. I'm questioning if I should furr out the rafters to obtain the specified thickness of spray foam, or if setting up a number of inches of polyiso foam into the underside in the rafters, after the spray foam, could operate?
If you need to endeavor a midway Answer that may or may not operate, you'll be able to cut out several of the drywall near the ridge, and set up spray foam insulation on the underside on the roof sheathing, just in the region near the ridge beam.
Should i absolutely guidance sheathing seams parallel into the ridge line, for sheathing higher than an air gap? Wouldn't that isolate the air under Just about every sheet of sheathing, and is the fact okay?
I believe that folks who write developing codes are worried that, If your code will allow unvented rafter bays to be insulated with cellulose, failures will come about due to sloppy cellulose installation.
Vitality codes create minimum R-value prerequisites for roofs and ceilings. There are various feasible code compliance paths; most builders select the prescriptive route, which sets forth least R-values for useful reference roofs and ceilings within a prescriptive table.
The plan: Portion A: I discovered 1" Dow rigid foam backed five/8CDX for the same value since the bare CDX, And that i plan to double it up just like a SIP, installing The underside sheet foam aspect up and the subsequent sheet on leading (staggered not surprisingly) Along with the foam facing down, offering me two" of insulation involving the plywood.
The best way to move forward could be to settle on a far more vapor-permeable sheathing materials -- anything like click here to find out more fiberboard.
You can skip the tape on the top layer of plywood to exact some time and money. Which is in all probability what I might do if I had been you. That said, there is no hurt in taping the seams of the very best layer read more of plywood.
Q. "I are already applying rigid breadboard style expanded polystyrene within the rim joists and imagined exactly the same could possibly be place beneath the sheathing amongst the rafter bays."
I question which the condensation is going on from the cold ridge beam. Relatively, I think it is likely that condensation is going on about the underside of the ridge shingles or perhaps the underside with the asphalt felt underlayment.