Retrofitting new wall inside existing frame
I have an interesting challenge in my 1941 1500SQFT energy retrofit in Minneapolis (Zone 6-7). I want to maximize realistic R-value while preserving the existing siding and sheathing, which we can assume has no vapor barrier (this will be verified when we open it up). While I would normally prefer to wrap the exterior, this is not possible at this time. There is no historic value to the plaster/sheetrock, and we’re demoing kitchen and bath anyway, so I intend to do all insulation from the inside. The home is all 2×4 16″OC construction with old yellow fiberglass batts. Adding wall thickness to the inside is acceptable, although 2″ more is preferable to 4″ more. I’m not looking to get certified, but want a very comfortable house with a chance of 15-20 year payback.
Here are some options I’ve considered:
1) Do nothing with the walls and focus on the roof and air sealing – this is the adivce that most local builders have given. Most have never heard of passive house and think US building codes are too strict. Some, however, have cited the valid reason of opening a can of worms with wiring, etc.
2）卸下现有的板岩和玻璃纤维。喷涂R-21的2×4壁。这可以保留内部尺寸并提供真正的蒸气屏障。跌倒是为了获得R21而进行的很多工作，而且仍有很多热桥进行。
3）在＃2中执行所有操作，但然后添加2.0英寸EPS泡沫的内层以停止桥接并使我们进入R-33。我喜欢这个主意，但我认为这可能会使干墙和厨柜上的泡沫很难。这需要框架工作吗？
4) Don’t gut anything, but build a new stud wall inside the existing and spray foam that for R38ish Maybe this is crazy, but it might save some on the demo side, and would allow us to further insulate in the future from the outside (we will eventually need to touch the siding). It also limits the can of worms effect (good and bad). Is this even possible? It seems to me that it shouldn’t cause any moisture issues since there is a full interior barrier and no exterior barrier. There would also be no thermal bridging as the studs wouldn’t touch. Thoughts?
5）最终解决方案是将所有东西肠道，建造新的双层壁并喷洒整个东西，或者将泡沫和另一种材料（细胞糖？）组合在一起。这可以使我们进入R-40至R-50范围。
Please let me know what you think of these scenarios given the information provided, and the desire to keep this semi cost effective. Thank you very much for your help here!
GBA细节库
由气候和房屋部分组织的一千个建筑细节的集合
答复
回答1是一个合理的答案…你也可以有限公司nsider things like adding PV and and air-source heat pump and seeing if you can have a better energy impact for the same cost that way.
其他选择似乎包括喷雾泡沫。喷雾泡沫仍然使用高全球吹热撞击剂，因此很难证明使用它是合理的。您可能会通过任何这些设计来增加房屋的全球变暖影响。
EPS does not have that problem. So what about doing something like #3 without #2: Add EPS inside with taking the drywall off or changing anything inside the wall? The wiring isn't a big deal--just add box extenders to bring the box through the EPS. Sure, those will be air leaks but not as bad as they are now if you do a little sealing while you are at it. You can attach drywall by gluing, add furring strips to attach it to, or use a product like R-etro that is EPS with built-in plastic support for drywall. Kitchen cabinets would require better support, so maybe that part has 2x4s turned sideways as the furring strips.
有了任何内部绝缘材料，您将在内壁穿过的地方进行热桥，但这并不是一个巨大的问题 - 您仍然会使它变得更好。
You could also do a double wall, but I'd be inclined to leave the existing wall, sheetrock and all, in place, and just build the additional wall however far in you are willing to go, and fill with cellulose. The sheetrock perhaps adds some thickness without adding much R-value, but it's not hurting anything either.
感谢查理的深思熟虑。我喜欢使用刚性泡沫的想法，但没有看到这样的内部。
这对喷雾泡沫冲击很有趣。我一直认为，整个生命周期的能源和温室气的节省会迅速抵消初始体现的能量/碳。您是否知道有任何对此做出确定答案的研究？
瑞安，
有关某些喷雾泡沫产品和XPS中使用的吹剂的全球变暖潜力的更多信息，请参见：
避免绝缘的全球变暖影响
Calculating the Global Warming Impact of Insulation
Martin,
感谢您的链接。我也很想听听您关于在现有墙壁内部使用浓密的刚性泡沫的看法。我听说Polyiso的影响最低，但后来有些人说它将缩小，这使得它不适合此应用程序。EPS似乎没有我想要的R值，但也许是一个更好的选择？需要明确的是，我正在考虑在带有旧玻璃纤维的3.5英寸墙的内部添加4.0英寸（两个2.0英寸的床单）另外的R23，而EPS则是额外的R15。我仍然会喷涂轮辋托梁，after子在那里与墙壁和我可以访问的任何其他缝隙相遇。
对于Ryan关于体现能量的问题的更直接答案：喷雾泡沫的问题不是体现的能量。它是气体填充泡沫中的气泡。正确的是，与一生中节省能量相比，绝缘的体现能量通常很小。但是，泡沫中气泡中气体的影响> 1000 x，因此可以很重要，如马丁提供的链接中所述。