在热水气候中的空气密封
我’m about to start having my new house built and I’m working with a friend who is very flexible, but not very knowledgeable about building science.
我could use zip system and tape, but for $32 a sheet, this is pretty expensive. I could also use regular osb ($17 sheet) and 1″ of spray foam. I could also maybe use regular osb and external used iso foam sheets, but I’m not sure how these are normally sealed. These seem to be good sealing options, but maybe there are better ones.
我知道喷雾泡沫可能比Zip贵，但我不介意此或ISO的额外R值。
What’s the most cost effective sealing for a hot humid zone?
Thanks so much for the wealth of info here!
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Replies
Kman91,
Any of the sheet goods used as sheathing (plywood, Zip, regular OSB) can be taped and used as an air barrier. You can also use a variable-perm membrane as an interior one instead. Both approaches work if done diligently. The key is to make sure the air-sealing is continuous, and to think through how that occurs at the transitions between the foundation, floors, walls and roof.
感谢Malcolm，我想一次使用胶带或胶合板录制，感谢您的确认。我在ZIP中的一部分（我喜欢这个概念）是安装。本地建筑商，至少我正在使用的建筑商，没有在拉链中经历过，因此钉子过高，没有卷曲的胶带等。费用可能过高，也许不是最好的解决方案。我可能只需要现场，并确保他们做对了（至少在我可能的时候/何时）。我也完全同意连续密封零件。谢谢！
“我可以使用邮政系统和胶带，但每张纸32美元，这很昂贵。”
When I drive by all the new apartment/ condo projects I never see OSB and house wrap any more. When they build that many square feet the pencils get very sharp looking for even the smallest costs. Small saving turn out to be what I would call big money and all I see is ZIP.
My guess is buy the time they add the house wrap and the labor to install they come out ahead.
我个人认为，新建筑计划中的喷雾泡沫是一个危险信号，可掩盖不必要的昂贵材料。在我看来，懒惰加上对预算等于喷雾泡沫的蔑视。
Almost every problem in new construction can be done better at a lower cost while avoiding spray foam.
Since you are in Texas can I suggest you not be a lemming and spend the time to find a way to keep the HVAC equipment and duct out of the attic and avoid applying spray foam to your roof. This will allow you to fill the attic with R60 of cheap fluffy insulation and cut the electric bills by 40%.
Walta
我agree that Zip can/may be less costly in installation when pricing is more normal (pre covid). I wonder if it's still true now? I guess I could do a hybrid approach like Malcolm suggested with taped regular OSB and house wrap. I'll have to get some cost estimates.
我的原始计划确实涉及通风阁楼并密封天花板，以避免喷雾泡沫成本。感谢您对这个想法的投票。我的问题是弄清楚如何将交流放置在内部。然后，我的想法是2个AC单元（2800FT2），位于2个壁橱中，并在这座高天花板房（浴室等）的降低天花板室里运行，因此可以做到。我不确定如何密封它，但是我想可以使用填缝边缘使用标准的胶合板或OSB？我喜欢迷你拆分的想法，但不确定如何将其带到所有房间。一旦迷你拆分被管道造成，似乎损失了一些好处。
When thinking about ducts inside and sealing the attic floor (for a vented attic), I think this is a strong option, building a flat roofed box (with a great service cavity for ducts and electrical) then adding the roof trusses. I think this reuses skills and practices familiar to the most trades.https://www.finehomebuilding.com/project-guides/insulation/simple-air-sealed-ceiling-for-a-high-performance-home
Completely agree on avoiding the "head in every room" mini-split approach. Ducted mini-splits vs small multi-position air-handlers probably come down to installation location and whether you have good, clear, access from below and a filter grilles approach (horizontal ducted) or whether you have access from the side and an accessible central filter location.
Unducted returns can be done with either equipment (Fujitsu ducted minisplits can go vertical, Mitsubishi can't but they have small multi-position air handlers that can). Short jumper ducts through the deep service cavity can give good return paths (without severe door undercuts).
Oh, and if you think managing the nail depth on Zip is hard, won't you have to do the same on the OSB and then manage/inspect/worry about the house wrap. Zip at least is one system with one set of instructions ...
That is a cool idea, thanks for the link! I'm not sure I need that level of access, but it's great to see how someone has done this.
>Ducted mini-splits vs small multi-position air-handlers probably come down to installation location and whether you have good, clear, access from below..
Agreed, although I'm not sure how many installers here know about mini splits. I hope there are more, but currently they don't even want to deal with 2 speed systems (my current system). There are so many AC options.
我'm glad to hear you talk about the idea of in-ceiling or in-wall ducting for return paths. I haven't heard much about this, but I've done it in a few rooms even in my current house (door undercuts are not sufficient). I wonder why there's no one doing small quiet fan systems for this kind of thing. It would greatly enhance a non-ducted mini split installation to expand it to a few rooms.
>Oh, and if you think managing the nail depth on Zip is hard, won't you have to do the same on the OSB and then manage/inspect/worry about the house wrap.
Nail depth on OSB isn't important since it doesn't impair the water barrier from doing its job like it does on Zip, but yes, house wrap can definitely be done wrong as well.
Zip pricing must vary regionally, but here its at least 2x as expensive as commodity OSB right now. I was discussing this with a friend, and I think there are a lot of factors to consider -
1. If you're paying someone for their labor, it's probably a wash whether it's zip + tape, or osb + tape + housewrap. If you're doing the labor yourself, the material costs are lower for tape + osb + housewrap.
2. I'll throw in another observation point to Walter's - there are about 10 apartment complexes / hotels going up on my drive in to work, a few of them are using Zip, some are using Typar, and some are using Tyvek. With the current price swings I'd say those decisions are made only a few weeks at a time.
3. If space is a concern, there are ways to put the ducts in the attic, you just have to seal them well and bury them pretty deep in the insulation. This isn't my favorite detail, as repairing anything becomes a real chore, but it can be done.
Thanks Kyle, I think you're correct on all counts.
Zip here is $32 vs $18 as of today (it changes often), so pretty similar to your area.
我have reservations about blown fiberglass in the attic, since fiberglass not enclosed on all sides means you won't get the stated R value, but I guess cheap is a quality overcoming many faults, and it's still pretty good for the money. I may consider blown cellulous. It seems pretty cheap here too.
我agree, attic ducting can be done, and if I can seal them, then it's a done deal, even if they leak, they only leak down into the house (if I seal them correctly).
Part of my problem is that it's a T shaped house, and the smaller section has an upstairs room in the attic, so this will have to be an unvented section of attic, which complicates sealing and insulation. I'm in zone 2, so I could do dense pack cellulous and do a semi permiable membrane at the roof ridge, but that makes me a little nervous due to the moisture issue. I could also do the vented idea and seal the inside as Malcolm suggested, or do the June issue idea with dense pack cellulous. I'm not sure what's best.
供您考虑（关于OSB作为空气屏障）：
Study Finds OSB Not a Reliable Air Barrier.
Thanks Kiley. Interesting comments on that one. I'm not looking for passive house quality sealing, but it does raise some good points.
The major variable in all this is cost. Peal and stick WRBs, spray on WRBs, Zip (with integrated WRB). Ideally Zip costs will go back down again, but I wonder when or if that will be.
我今天注意到，现在有23美元的Forcefield在这里可用。我必须检查一下。看起来还有一些很好的文章，比较了Zip和Forcefield。