Air sealing exterior walls in a benign climate
Hello Martin,
I am removing and replacing the siding on an old Victorian located in Berkeley, CA which I believe is climate zone 3. After stripping off the old layers of siding, we will insulate, install plywood sheathing, (nailed at 4 at eh edges and 6 in the field for seismic stiffness), and then a drainable house wrap and fiber cement siding.
我的建筑师表示，我们的气候足够轻微，我们可以从安装得良好安装的BATT绝缘中获得的R-15应该在墙壁上充足，如果我们在密封外观的真正良好的工作真的很好的工作时，就可以充足。你同意？
I understand the use of sealing tapes that would seal all the joints and seams in the plywood and also the laps in the house-wrap. My other question stems from reading a number of articles in GBA which suggest sealing the sheathing to the studs. I have see several recommendations: one is construction adhesive (which dries hard and brittle); the other is polyurethane which stays somewhat soft ( but I don’t know for how long); and the 3rd is acoustic caulk which is supposed to stay soft forever. What do you think of this technique to prevent air movement between stud bays and which caulk or sealant would you recommend?
Thanks,
克雷格在伯克利，加州
GBA详细资料库
由气候和房屋部件组织的一千个建筑细节的集合
Replies
克雷格，
问：“我的建筑师表示，我们的气候足够轻微，我们可以从安装良好安装的BATT绝缘中获得的R-15应该在墙壁上充足，如果我们确实在密封外部的真正良好的工作时，请在外观上没有任何额外的泡沫。你同意？”
A. There is no single answer to this question -- other than the obvious answer that you are obliged, at a minimum, to meet local code requirements. If you were building a new house in Climate Zone 3, the 2012 IRC would require (according the the prescriptive requirements in Table R402.1.1) that you install at least R-20 insulation between your studs, or R-13 between your studs plus R-5 insulation on the exterior. So it's not crazy to consider installing a layer of exterior rigid foam or exterior mineral wool on a siding replacement job in your climate zone. Remember, you won't have another chance like this for about 60 years -- the next time your replace your siding.
Q. "My other question stems from reading a number of articles in GBA which suggest sealing the sheathing to the studs. ... What do you think of this technique to prevent air movement between stud bays?"
A. I don't know whether your house has no sheathing -- a fairly common situation in Berkeley -- or existing board sheathing. In either case, installing new plywood sheathing gives you an opportunity to add a fairly airtight barrier on the exterior side of your stud walls. If you have full access to the stud bays from the exterior -- in other words, if there is no existing sheathing -- I suppose that you could prevent air movement between stud bays by installing spray polyurethane foam between the studs. That isn't necessary, though. In most cases, simply establishing an exterior air barrier by taping the plywood seams is enough of an improvement to make a huge difference. Either Zip System tape or Siga Wigluv tape would be an excellent tape for this purpose.
空气密封现有的房屋很棘手。您的墙壁可能会在螺柱托架的底部附近有空气运动（泄漏允许爬行空气进入螺柱托架）或顶板附近的空气运动（进入阁楼）。如果可能，必须跟踪这些泄漏并解决。
没有门槛，突然间，绝缘体变得足够，而不是较少。它只是成本和能源使用之间的权衡。所以没有一个答案 - 这取决于你有多少价值减少你的化石燃料消耗，你想要保护自己，你想要保护自己免受未来的能源成本增加，以及你是否要支付现金或获得贷款支付对于工作，以及您使用的热源以及您的承包商如何高效且廉价地安装外部泡沫。但正如马丁所指出的那样，代码最小是一个很好的起点，了解一个好的权衡是什么，你可以决定是否要超越这一点，或者为了改造，可以走下去。
你问了密封剂。马丁建议胶带。如果您使用密封胶，请注意，标准声学密封胶非常臭，并且在安装后的几个月后仍然闻到数周。蒸气对你来说可能是糟糕的，尽管很难说，因为它们主要来自含有许多不同VOC的混合的原油。我最喜欢的替代方案是由475个建筑产品进口到美国的Contega HF。它停止味道很快，溶剂是乙醇，所以对你而言比禁止禁烟酒吧的空气更糟糕。
如果你和建筑带一起去，那里有OK录像带，那么真的很好录像带。一些测试完成，Siga Building Tapes非常好。我会为他们价格为看看你想出了什么。在封锁墙壁之前，你只有一个机会就可以做到这一点。
后续问题：我更愿意使用Polyiso进行胶合板护套的外观，因为它似乎具有较低的环境影响。1.箔面向面向是否产生不需要的蒸气屏障？2.如果我胶带胶带良好并提供一个带有1/4“捆绑的雨屏差距，我可以跳过房子包，并期望箔面向足够的WRB？
克雷格，
外部刚性泡沫的墙壁设计用于干燥到内部。Polyiso是蒸汽屏障的事实不会导致气候区的问题。
如果你想要,你可以外部泡沫作为一个细节water-resistive barrier (WRB), and skip the housewrap. However, if you decide to go that route, you should know that the details are somewhat tricky. Here is a link to an article that explains what you need to know:使用刚性泡沫作为防水屏障。