Insulating Walls Without Sheathing from Interior
I am renovating a 100-year old house near Seattle (climate zone 4 Marine). The house has wood siding nailed directly to 2×4 stud walls (no sheathing, no insulation, no tarpaper or other membranes). There are no obvious signs of rot or other water issues. The owner wants to gut the interior and insulate the exterior walls from the inside while leaving the siding in place. Of course, when I insulate these walls I want to avoid creating new moisture problems. I’ve been rereading all of relevant GBA articles I can find, primarily,Insulating Walls in an Old House With No Sheathing。//m.etiketa4.com/article/insulating-walls-in--rand-house-house-with-with-with-no-sheage
I’m tentatively planning to install Dorken Delta-Dry rainscreen against the inside of the siding.https://www.dorken.com/media/docs/products/product-details/delta-dry-brochure.pdfThe rest of the stud bays are then filled with closed-cell spray foam, as shown in the attached detail. The foam is applied directly to the inside of the rainscreen mat. Dorken’s technical consultant recommends this approach. It seems to meet all of the criteria described in Martin’s article. It’s similar to the approach demonstrated in this Matt Risinger video.https://www.youtube.com/watch?v=jhoQ_f9ZnzQRisinger drills vent holes in the top & bottom plates to increase airflow behind the siding, but I’m not planning to do this because Martin says not to!
Has anyone actually used the Delta-Dry product in this way? Any concerns or feedback to share? I’m slightly wary because even though Dorken’s technical staff recommend this approach, it seems that Dorken doesn’t officially endorse this use of their product. (E.G. I can’t find any documentation or details from Dorken showing the Delta-Dry product used in this kind of retrofit application.)
Another thing that bugs me is I don’t fully understand how water exits the wall after it trickles down the rainscreen and reaches the bottom plate. (Unlike a typical rainscreen in new construction, there are no weep holes.) I think the answer is “the same way it always has” — I.E. it collects on the plate until it evaporates or leaks out through gaps in the siding. Does that sound right?
P.S. The applicable codes are 2018 Washington State Building Code (IRC w/ state amendments) and 2018 Washington State Energy Code – Residential (IECC w/ state amendments).
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I'm not sure what the Delta Dry buys you in this case except for more cost.
文章的原始建议（拐角处的1x1条，泡沫/房屋包装量）大约是相同的工作，较低的成本，并且由于它是可渗透的，因此可以使您可以用开放式泡沫或蓬松的隔热材料隔离。这也使腔体干燥到内部和外部。
我发现一个技巧非常适合在这里构建屋顶通风口，这也可以在这里工作，这是抓住一卷房屋包裹，并将其切成斜切锯的宽度小于螺柱湾的宽度。现在，您可以在进行非常快速的安装时可以展开和钉书。
Thanks Akos. I'm sure you're correct about the "strips" method being more affordable.
I agree with Akos here -- adding a "rain screen" on the interior of a wall isn't really gaining you anything. A rain screen is supposed to help keep water out of the interior of the wall assembly, so putting the rain screen inside the wall isn't helpful. You're also correct about the "where does the water go?" problem here. I suppose such an installation would help ensure that only the lower part of your wall would rot out...
我会仔细检查外部闪烁的细节，并确保您已经完成了最好的工作，以防止水首先落后于该护套。用矿物质羊毛奶粉隔离，如果有任何水将其放入墙壁，这比玻璃纤维少。用填缝和罐装泡沫将空气密封老式的方式。这样，您就不需要任何喷雾泡沫，这将为您节省更多的钱。将其中的一些节省放入基本的内部智能蒸气延迟器（例如膜）中，以获得一些额外的保险。这就是我在CZ5中在自己家中所做的，然后再替换外部T1-11来获得刚性泡沫和新的纤维水泥壁板。
希望马尔科姆会看到您的帖子，并为您有一些想法。他在您的气候区域做了很多工作，并且知道在潮湿环境中工作的墙壁。
账单
Don,
The gap you create is primarily a capillary break, and to allow more drying. If the siding is so ineffective that the gap is necessary to drain bulk water then you should probably deal with that at the cladding layer, and not rely on the inverted rain-screen to try and solve the problem.
我同意阿科斯和比尔。一个简单的缝隙，尽可能少的桥接（由可渗透的挡板维持）也是我的偏爱。
感谢Malcolm和Bill。
I shouldn’t have referred to the Dorken mat as a “rainscreen”. I recognize that in this case it mainly functions to ventilate the back of the old siding.
听起来像是马丁文章所描述的垫片+刚性+巴特方法比Drainmat+Sprayfoam方法更可取。但是，似乎两种方法都有相同的“水在哪里”的问题，那就是水在盘子上滴下并收集。在马尔科姆（Malcolm）对无效壁板的评论之后，如果大量的降雨正在通过，除非解决覆层问题，否则不会进行隔离的内部改造，对吗？由于目前没有明显的腐烂，因此可以合理地假设现有的壁板是合理有效的（我希望）。
Don,
我应该澄清一下：您很可能会弄湿壁板的后部，甚至是窗台上的一些，但是只要有良好的干燥能力，可能不会带来太大的风险。如果您现在看不到任何腐烂，那么您的计划就可以了。
What type of rigid insulation would you recommend for the "permeable baffle"? I'd prefer to use XPS for the higher R-value, unless you think the permeance is too low.
Don,
再次考虑一下，如果您使用的是泡沫，我不确定挡板的渗透性很重要。只要您不包括内部蒸气棒，墙壁的两个方向都具有良好的干燥能力。
薄(1/2 "左右)unfaced XPS可能是好的。EPS would be more permeable. I would avoid polyiso in this particular application though -- foil faced polyiso is a vapor barrier because of the foil, and while the fiberglass mat faced polyiso is permeable, it's also not happy if it gets wet.
我认为，只要它不是箔或多面，就不会在这里选择刚性泡沫，假设它不是特别厚。
账单
Don,
Some of it depends on who is doing the work and how much that labour costs.
If you are paying for trades, I would go for 1x1 stick with stapled house wrap and fill the cavity with open cell spray foam. This seals up the assembly, uses a reasonable amount of polymer and gets you a decent R value assembly.
如果您正在看DIY，那么1x1+刚性+巴茨可能是最便宜的。削减和拼凑泡沫并将其密封到螺柱上的更多工作要做。
由于刚性在螺柱之间，因此您可以从木螺柱上获得热桥，因此刚性的R值并不重要。您可以使用Polyiso获得更高的空腔R值中心中心，但组装r值几乎没有budges。最好的是选择一个渗透性的泡沫，该泡沫是建议的波巴或厚度足以在您的气候中提供凝结控制的泡沫（在2个区域为2x4壁）。
Thanks again for the responses. It sounds like there’s no consensus about the importance of foam insulation permeance. The options seem to be:
• Use permeable foam to facilitate drying to both sides, or
•使用足够厚的不透明泡沫以防止冷凝，或者也许
• Trust that the assembly will always dry to at least one side without worrying too much about the foam permeance.
Good points, Akos. In your spray foam example, is the stapled housewrap necessary to protect the foam, or is it just there to create a gap behind the siding? My understanding is that it’s unnecessary to have a protective layer between the foam insulation (regardless of type) and the air gap behind the siding.
房屋包裹有许多目的。它可以用作壁板后面的WRB，因为开放的细胞喷雾泡沫可以吸收水。它提供了一个支持泡沫喷涂泡沫的后备，加上通风孔间隙。
The house wrap is only needed for a spray foam install. If you go with cut and cobble rigid insulation you can skip at.
Polyiso does absorb some water, but not as easily as many seem to think. I've used it over many years, and have observed many situations where the exposure to water varied. My experience is that unless it is literally trapped underwater the penetration of water is all but negligible. So it makes good sense not to use it under a slab, for instance, but even leaving it in the rain is no worse than exposing any wood to rain. It will take on some moisture, but it will dry at about the same rate, once protected, as lumber. I have seen that EPS will also get waterlogged underwater unless it is a dense formulation.
Adding another detail drawing of the "indoor rainscreen" (with fire blocking) from this post:管理水和绝缘墙壁而无需护套。