Low-Slope Roof Insulation Retrofit

Jonny_H|发布GBA Pro Help上April 22, 2022 08:06pm

Zone 5 (Ohio)

A section of my house has a low-slope roof (just under 2:12), with a couple layers of built up roofing of some sort (asphalt-y / granular lower layer, somewhat more rubbery but still tarry upper layer). We are planning on adding 6″ of reclaimed polyiso on the exterior to supplement dense-packed cellulose in the 2×6 rafter space to the interior. I understand that the key to this assembly is a robust air barrier at the structural sheathing (under the exterior insulation); on the remainder of the house (walls & steeper roof) we’ve been stripping everything back to the sheathing and applying Proclima Adhero to the sheathing as the primary air barrier.

但是，在低空区域，在研究了几个小区域之后，现有的屋顶很难去除 - 上层可以剥落，但下层牢固地粘附（以及钉子），想要分成碎片，只能逐渐慢慢刺入英寸。

Is the existing roofing, which is in reasonable shape / isn’t leaking anywhere, a sufficient air barrier on its own, such that I could just attach the Adhero coming up the walls to the roofing, or would I need to cover the entire roof (over all the existing roofing) with Adhero as well? Are there any other potential downsides to just leaving the existing roofing in place and doing my insulation and new roofing stackup on top of it?

Thanks!a

回答

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Replies

杰米B|Apr 23, 2022 02:57pm|#1

Hard to tell without photos and a brief description. Btw, a built up roof is hot tar/asphalt and loose laid gravel on top, it's common in large commercial, very rare in residential. It sounds like you might have a touchdown modbit roof.

无论如何，这是代表您在现有屋顶状况的情况下按照您的判断。但是，如果您认为这很好，我个人认为可以离开就可以。

Yes it is vapour closed and waterproof. But you'll have to think about how you're going to fasten the foam layers to your roof membrane. If you're screwing down then it won't be so waterproof anymore, which is only useful as a backup layer to your new roof layer. This still might be your best bet vs glueing down the foam cause it might not stick to the modbit roof. Again hard for me to tell from where I am.

然后考虑您的栏杆，以及围绕它的细节。围绕水管理的详细信息，（即您是在阻止Scupppers吗？还是您必须重做牙龈，您将要贴上什么）

And then what is your new roof layer going to be? You'll probably need a protection board on top... If it's mod bit torch down, you'll probably need asphalt protection board so your roofers dont light all that insulation on fire. Or something like tpo, I'd still suggest putting down plywood so walking on it doesn't ruin the insulation or footsteps don't stretch the membrane. And then details like how that ties into your parapets, etc.

可能会考虑一些泡沫的地方哭泣的孔。如果您的主要屋顶膜确实在某个时候泄漏，那么您的Polyiso会吸收水，并且它的绝缘能力会降低。而且您永远不会知道这一切都被吸收了，因为您的底部屋顶层停止了水。

杰米

Jonny_H|Apr 25, 2022 07:38pm|#2

Thanks Jamie! I've attached few photos of the situation to this comment.

Thanks for the clarification on terminology, after googling around a bit I think you're right, its either mod-bit or rolled roofing (or one on top of the other).

该计划一直是拧紧泡沫，因此那里没有任何粘合剂兼容性的问题，并且总是会有紧固件穿透任何空气屏障膜层。为简单起见，我们在低矮的和陡峭的屋顶上都使用相同的堆栈 - 两层polyiso层，上层嵌入了2x4的层，固定在下面的结构上； 1/2”。钉在2x4上的胶合板护套。低斜率部分将获得EPDM膜。这不是一个真正的“扁平屋顶”，带有栏杆和那些类型的细节，它更像是一个大的“棚屋”，坡度略低于2:12 - 我确实必须重做牙龈和一切。我们切断了旧的悬垂，正在建造新的悬垂。

Good point on not noticing potential leaks -- you convinced me to leave a couple little holes near the edge that could be periodically inspected for signs of water leakage.