"R-19 batts are quite air permeable, and on very long unobstructed rafter bays you have got really a stack influence. It doesn't take a big number of air leakage to provide some drying there. Also, In the event the batts are unfaced or kraft-faced, the drying towards the inside could well be significant.
More info on how to insulate an unvented roof assembly is supplied in the short article on this site.
We really Really don't know if these roofs have correct vent channels, or what type of vent baffles (if any) ended up employed to maintain the air flow hole in between the best of the fiberglass insulation along with the underside on the roof sheathing.
Also, why not zip panels taped and afterwards roxul batts with drywall more than that. Roxul is brilliant stuff I have been tests For many years in mad methods endeavoring to see its capabilities. I think that zip panels, taped adequately, with roxul batts will past providing the roof!
Can I get some a lot more commentary to the "whole roof" of Ice & Drinking water Shield? I believe this experienced hardly any to carry out with the failure. The rationale why I question is I have a similar "total roof" layout arising, Having said that, the rafter bays are all straight runs with soffit vents, ongoing vent baffles (1/two" plywood) and continuous ridge vent. Dense pack cellulose, two" XPS down below 2x10's, air tight drywall (XPS can be sealed up much too).
You will be describing a cathedral ceiling that includes all attainable faults. There was no awareness to air sealing. The worst achievable insulation was applied (fiberglass). And the roof assembly is unvented. So it truly is no surprise that you'll be viewing condensation.
Martin, because of your great and well timed tips, we are actually headed toward a solution of rigid foam around the outside of your ceiling. Thanks for pointing me With this new and improved route. We are still Doing work out some aspects, for instance...
The vast majority of the data I operate across is apparently with the cellulose field that claims wind-clean is a huge problem with fiberglass; click this link and from your fiberglass market which asserts the cellulose team overstates The difficulty Which to the extent wind-wash occurs it is actually inconsequential.
Because a roof assembly won't Stick to the principles set up by the making code or suggestions of developing researchers doesn't suggest the roof has
The specific design demonstrated was to get a Passive Residence. The roof thickness & use of a provider cavity could possibly look like overkill for many projects, but If you'd like an airtight lid, a service cavity can get you there - permanently... And assist you to wire and light the inside.
In case the air inside of my property was humid unconditioned air, I would be Similarly involved. But would not The within air be somewhat dry because of the on-going air conditioning? Really should I be troubled out condensation forming on my AC ducts if I cathedralize my ceiling?
Thanks, Martin and Stephen. The good news is we've been within a problem the place we can easily pause and rethink, as The brand new felt has become placed, Nonetheless they haven't started setting up shingles nevertheless. I will talk about the problem Along with the contractor once more. I may be able to get him to rethink.
I've a point for blueskin, like a both equally an air and vapour barrier, but additionally it will work as a seal to the screws that maintain every little thing down. In reference for the vaulted schematics on This web site, it shows vapour/air barrier on top of insulation, which received me asking yourself. Nearly as good as I am installing components, no one is ideal, and an air leak may establish in between XPS seams. After ANY moisture will get all the way down to decrease sheathing, it's recreation more than.
Keep in mind: Simply because your roof assembly is dry, does not imply it is actually well insulated. Your assembly could have huge air leaks that work as thermal bypasses. (Or not. It is really difficult to tell and not using a site go to.)