You have lots of restraints, and people restraints are leading you to some convoluted wondering. In lieu of advising you to definitely adopt a number of compromises, I'll make clear the right way to address your roof, even if the appropriate way is expensive.
Inside of a phrase, no — the code explicitly forbids this process. Cellulose can only be used in an unvented roof assembly if there is an enough layer of rigid foam previously mentioned the roof sheathing or an ample layer of shut-mobile spray foam under the roof sheathing. Cellulose by yourself won’t get the job done.
Thanks for that suggestions. We will never A/C the setting up (Will probably be photo voltaic driven). The wind is really continual, however it is a humid surroundings, so moisture Regulate is undoubtedly on my thoughts.
The key flaw Within this roof seems to be to generally be the ice and water membrane at the best level while in the rafter bays. Would just regular felt paper have authorized plenty of dampness to dissipate throughout the roof sheathing staying away from rot?, I sort of doubt it.
A. You should only use an set up system that your insulation contractor is aware of. Below while in the Northeast, many contractors would almost certainly fill your rafter bays using the dense-pack technique soon after your new roof sheathing was installed.
I have developed dense-packed unventilated roof assemblies many occasions with no dilemma. Not surprisingly I have never torn into them either. I would want to see much more examples of failures in these kinds of assemblies when they're around.
I've read too many experiences of homeowners with problematic SIP roofs mounted in the eighties -- Many of these roofs are actually rotting on the seams due to condensation of dampness from exfiltrating inside air -- to sense comfy recommending a SIP roof.
Install rigid foam insulation earlier mentioned the roof sheathing and air-permeable insulation amongst the rafters. This type of assembly is meant to dry to the interior, And so the assembly need to by no means contain an inside polyethylene vapor barrier. If you select this method, it’s probable (however not see this site needed) to install vent channels among the highest with the rigid foam and the highest layer of roof sheathing by installing a number of parallel 2x4s — a person higher than each rafter — extending from soffit to ridge. (For more info on this method, see How to put in Rigid Foam Along with Roof Sheathing.)
Thanks for the prompt addition towards the list of materials for producing site-constructed vent baffles. I have edited the textual content of my blog site to include your recommendation.
"When you have mounted the code-mandated thickness of rigid foam above your roof sheathing, you’re free of charge to set up as much fluffy things as you want amongst the rafters."
It sounds like an excellent approach. Based on which kind of rigid foam you choose, you will end up getting insulation from the number of R-sixteen to R-24. While that is a lot less than code specifications, It really is Considerably, a lot better than what you've got now.
A. The polyiso will not likely produce a mildew problem. If you are suitable that black struggling with will not give a radiant barrier, the difference in efficiency when compared with foil-confronted polyiso would be small.
Condition comparable to Eric, previously mentioned. If closed mobile foam is sprayed or "cobbled" from xps, do You need to fill all the Place, or only to thickness for preferred R worth?
Really should i thoroughly support sheathing seams parallel towards the ridge line, for sheathing previously mentioned an air gap? Wouldn't that isolate the air below Each individual sheet of sheathing, and is the fact that ok?