We will give it a check out. Existing can be a fourteen year old roof with 2" of closed mobile roofing foam using an acrylic elastomeric coating.
Thanks, Martin and Stephen. The good thing is we are within a situation exactly where we can easily pause and reconsider, as The brand new felt is positioned, Nevertheless they have not begun setting up shingles nonetheless. I will talk about the situation Along with the contractor once again. I may be able to get him to rethink.
If you choose to install open up-mobile spray foam in place of closed-mobile spray foam, your roof assembly should be able to dry fairly to the interior. Just make sure that the spray foam layer is thick sufficient to maintain your rafter bays higher than the dew level during the winter.
Since I've explained the correct way to get it done, I may also Allow you to realize that A lot of people have carried out That which you propose.
It appears if 1 have been to implement dense pack cellulose in a very vented cathedral ceiling the vent channel product must be rigid sufficient to withstand the tension.
two. Everytime you install fiberglass batts, air boundaries are a lot more vital than vapor Management. You need a superior air barrier on both sides of your respective fiberglass batts.
Outstanding posting and discussion. I've a matter about an current unvented attic assembly. The rafters are 2x4's along with the bays concerning them are absolutely stuffed with closed cell spray foam. I would want to add two 1in layers of polyiso to the interior of attic and then protect which has a vapor open membrane to airseal the assembly.
Of course, you can expect to continue to have thermal bridging through the rafters. But you will not have any dampness issues.
This is certainly a sophisticated matter, and If you're worried about code requirements within your town, then by all signifies you should question this problem at your local setting up Business. Normally, renovation do the job may be done without the need of bringing all areas of your property approximately existing code needs.
BTW, to the foam form, I am leaning towards XPS since one) I hold the perception that ISO is relatively fragile, for example if it gets in the slightest degree wet, and a couple of) the opportunity of long-term outgassing with ISO. Ideally any these types of outgassing would go upwards and outwards rather then downwards into your home inside, but the prospect that it might outgas into the interior really anxieties me.
I think that Invoice Rose is correct: all of these failures involve dampness which is carried by shifting air. These are definitely not diffusion failures. Should the rafter bays really are effectively dense-packed -- a large if -- the possibility of air motion is rather reduced.
It really is surely not restricted to an R 80 Passive House roof. Choose out the parallel chord trusses and slim it up.
"The normal roof air flow need Utilized in constructing codes and asphalt roofing companies requires 1 square foot of "Web absolutely free ventilation space" For each three hundred square ft of ceiling space (attic flooring spot) when vents are evenly divided — 50 percent of these large on the roof for the ridge, gable, or even a superior roof, and half minimal on the roof in the eaves.
Also, Why don't you zip panels taped then Full Report roxul batts with drywall around that. Roxul is brilliant things I have already been testing For a long time in mad methods wanting to see its capabilities. I think that zip panels, taped effectively, with roxul batts will last providing the roof!