EPDM屋顶带双蒸气屏障
我在2号气候区，炎热而潮湿。
我房子的一部分有一个EPDM平坦的屋顶。EPDM直接粘在胶合板甲板上。EPDM下没有外部绝缘。
I now need to insulate my 2×6 rafter bays. My spray foam guy recommends using closed cell foam. He says in the winter time, interior moisture can travel through open foam and cause mold issues on the plywood by condensation, since no exterior insulation was added between plywood and epdm to keep the plywood warm enough.
While I do get his point, wouldn’t closed cell foam create a double vapor barrier since I have EPDM on the outside of the plywood? If the EPDM ever leaks, there would be no drying potential to either side, correct?
我应该用开放式或闭孔泡沫吗？
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答复
No one have any insight?
因此，我在同一房间的墙壁为2x6，外部有1.5英寸的polyiso。我肯定会在那里使用开放式牢房，因为它便宜，而且我认为我不需要关心凝结，因为我有足够的外部刚性泡沫来保持床单温暖，正确吗？我仍在试图将所有这些的身体方面缠住。
嗨，Quantumgirl，虽然我不能专门针对您的详细信息，但我认为Martin Holladay的这篇文章可能会有所帮助：//m.etiketa4.com/article/sandwiching-roof-sheathing-two-impermeable-layers
And, it may be helpful to list out the full assembly details of the wall just so that we’re not overlooking a critical detail. .
感谢你的这篇文章。似乎马丁说，只要屋顶不泄漏，双蒸气屏障不一定是危险的。EPDM是一项DIY工作，尽管我觉得自己做得很好，但我可能不相信过去20年。
就我个人而言，我会使用开放式填充泡沫感到更安全，因此可以更轻松地识别出屋顶泄漏，并且我有内向的干燥选择。我希望我能在EPDM下方添加外部绝缘材料，但是现在为时已晚，因为我已经在顶部建造了一个甲板。肯定在我的策划不佳。
您认为，更可能是一个更容易的问题：1）使用闭孔泡沫时的屋顶泄漏，并且没有干燥的潜力。2）从冬季带有开放式细胞泡沫的内部水分的凝结问题？
I think I did a better job with the wall assembly, after doing a lot more research:
2x6 stud wall construction, plywood sheating with taped seams, Tyvek, two 3/4” layers of poly Iso with offset and taped seams, rainscreen with 3/4 treated ply furring strips, hardie siding.
And I plan on filling the entire wall cavity with open cell spray foam and then Sheetrock. Does that sound like a good wall assembly? It’s actually gonna give me way more R value than the required R13 for my climate zone. Are there any cons to having too much insulation?
I believe your roofer is correct: that un-insulated plywood would be a condensing surface for any interior moisture, and that open-cell spray foam won't do much of anything to stop it from reaching that surface.
As for the discoverability of leaks with/without closed cell spray foam, Martin Holladay responded to a post (#2 in the comments) regarding that. There's more to his answer, but basically he said this: "Eventually, all roofs leak. If your roof eventually develops a leak, you will know it. The first sign is usually a stain on your ceiling. These facts are true whether or not your roof sheathing has been sprayed with closed-cell foam."//m.etiketa4.com/question/how-to-detect-a-roof-leak-after-having-the-underside-of-the-roof-deck-sprayed-with-closed-cell-foam
It seems like you're damned if you do/don't relative to leaks, (although I understand your anxiety relative to the deck up there…) so it would make sense to me to focus on preventing the vapor reaching the condensing surface of the plywood.
Also, in a 5.5" deep cavity, it seems like you'll have trouble achieving r-38 with open-cell. Closed-cell will just get you there, so there's that benefit as well.
在您的墙壁系统上（从我对它的理解中听起来很棒），除非外部与室内的比率失效，否则我认为绝不可能的隔热效果不大。但是，这不适用于1-3区，因此您将其设置在那里。您可以提出一个论点，即您可能处于投资回报率下降。Beopt软件可能会告诉您该线路在哪里。
One other thing to mention is that given your wall system, you don't really need to use spray foam. You're probably aware, but it has much higher embodied carbon than diy-options like mineral wool or fiberglass. And if you're already paying for an installer, you could always switch over to dense-pack cellulose, which is super low on that scale. Just something to consider. In any case, as someone with a very leaky r-13 assembly, I'm jealous of your wall.