Intello plus for cathedral ceiling
Hello. I am taking down my cathedral ceiling and have been going back and fourth on the best way to insulate it. I have always wanted to avoid spray foam but venting will be hard because I don’t have enough rafter space to get to the R-49 I need with space for baffles.
I recently had a call with a building supply company that sells intello plus smart air and vapor barrier (call was with an architect), and they are suggesting that I use their product in lieu of venting or cc spray foam. Essential the assembly would be what I detailed below. This sounds great and would eliminate spray foam and the need for venting but I can not find much on proof of assembly. Do you think this is too risky? I could also add a vapor diffusion port but they are not recommended in my climate zone. Curious what you all think. I am already taking down one assembly that did not work and would rather not do this work again. Thank you!
Cedar shingles
cedar breather
felt
no air gap
r-49 batt insulation no Kraft
Intello plus as an air barrier
painted sheet rock
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Replies
BPortnoy1,
I assume you need R-49 to meet building code requirements. My understanding is those same codes preclude un-vented assemblies using batt insulation.
Hi Malcolm- yes R-49 to meet code. Without the air space I will have enough room for R-49.
Do one of these five:
https://www.greenbuildingadvisor.com/article/five-cathedral-ceilings-that-work
Intello isn't impermeable enough or smart enough to make up for the lack of vent or closed cell foam.
its crazy because the company seems so confident it will work but I guess its too good to be true. Do you think its better to go with R-38 and have the vent space or use spray foam and get the R-49 but no venting?
BPortnoy,
If the company is confident in their product in these sorts of situations they should lobby to get the assembly code approval. Recommending solutions that don't meet building codes is irresponsible, whether they work or not.
It seems like you are going around in circles. This is one of several threads you have started on the same subject, and you don't seem satisfied with the advice you are getting as the same ground gets traversed. As has been suggested in each of these discussions, your choices are basically to pick one of the assemblies in the link DC provided above in post #2. If you don't have the depth to use a vented assembly, have you considered furring down the rafters?
I will look at that as an option. Thank you
ProClima does promote the idea of using their air barrier on an unvented assembly, even in northern climate zones. In conjunction with dense packed cellulose, but not sure about with batts.
I believe Everett used this assembly on their build. If I remember right, he has intello on the inside with plywood/mento on the outside. 16" of dense packed cellulose in between.
https://www.greenbuildingadvisor.com/green-homes/a-first-time-builder-demonstrates-keen-understanding-of-building-science