Closed-cell vs. open-cell foam for insulating mudsill/rim joist
Hi there,
I’ve been working with a spray foam contractor to insulate the mudsill / rim joist area on the top of our 1890’s home in Boston (climate zone 5a). The house has a fieldstone foundation, with large beams (directly contacting the foundation) that serve as both mudsill and rim joist. We have the typical high humidity in the basement as one would expect. At this point the basement is unfinished, although we have a vision to finish it at some point in the future.
The contractor recommends open cell foam (8 inches depth for R-30), and while he understands the value of closed cell in preventing winter condensation, he says that the depth of the open cell would suffice as a vapor retarder. Is that a reasonable proposition, or should I be pushing for the use of closed cell?
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由气候和房屋部分组织的一千个建筑细节的集合
答复
如果协调完成，则最好在此位置进行闭路。
泡沫家伙在从开放式牢房开放时必须切换和清理软管，反之亦然。他们不喜欢做的事情。
I really dont care if they want to, they must do it for a rim joist area as far as im concerned!
8 inches of open cell spray foam would still be pretty permeable (~8 perms), and so is vulnerable to some winter condensation. By code, you would need to use a class I or II vapor retarder on the interior of the assembly to reduce condensation risks.
开放的细胞泡沫太蒸发了，无法在冰冷的田地石材基础上使用。在整个冬季，它将在寒冷的泡沫中积聚水分，并且不需要太多的水分或太多的冻结/融化周期才能与石头分离。（尽管大多数水分都进入木材，但通常会粘在木头上。）
这肯定需要一个封闭的单元溶液，至少是总R的前30％。代码最低为R15，它几乎可以使用2英寸的HFO爆炸闭孔泡沫（R13.8-R14）。这更昂贵。超过8英寸的开放单元，但是无论如何您都不需要R30，尤其是如果您不积极加热和冷却地下室。
When it comes time to finish out the basement installing a studwall as close as possible to the foam and use blown fiber insulation to raise the performance. It would be fine up to an additional ~R30 of fiber insulation before wintertime moisture accumulation at the foam/fiber boundary at the above grade section becomes an issue.
Beantown地下室的高湿度通常是夏季空气泄漏问题。虽然密封和用2英寸的闭孔密封和绝缘后仍然可能需要一些机械的除湿功能，但它几乎不会是以前的。
删除d
主题评论。...上周末我们在梅德福和萨默维尔开车，因为我的孙女在NCAA D3女子的曲棍球季后赛中为塔夫茨的曲棍球季后赛。在旧房屋（大概是世纪之际）又一扇门的距离似乎很少，似乎是重新侧面或正在重新铺设和新的窗户安装的街区...。不是新的壁板。看起来像是大量的一般升级和节能的改进。顺便说一句，她的团队从周六开始前往弗吉尼亚州NCAA半决赛和决赛。
可能有一些更新。很高兴看到这些历史悠久的区域得到恢复，那里有很多整洁的旧建筑。巴尔的摩的联邦山区是这样的，几乎整个地区都经过了重新设计，现在真的很好 - 而且已经完全占据了。很高兴看到。
Good luck to your granddaughter and her team! If you like seafood, there are lots of great places in Maryland and probably the eastern side of Virginia too.
Bill
Having lived in a few of those old triple deckers & duplexes in Somerville (as rentals) I can vouch for just how much low-hanging fruit there is on the efficiency tree there is for most of them. As condos or single-family homes the budgets for fixing the comfort and efficiency problems of that housing goes way up. I can't quite believe what some of those places are selling for now compared to their assessed values ~30 years ago when I helped a family with a full-gut rehab on a house in North Cambridge. The concept of "affordable housing" starts to feel pretty academic in those former working class 'burbs. (Affordable for whom?) Could former Somerville mayor, former congressman Mike Capuano afford to buy his own house now? Maybe...
解决该住房库存肯定要比在波士顿一些不密集的郊区中进行的全面淘汰赛，取代完全淘汰的毫无用处。
是的，现在，美国的po必须在（非功能）曲目下更远的赛道
如果外部包裹在脸部polyiso的2英寸中，是否会将建议从闭合细胞更改为开放单元？然后需要干燥到内部吗？
I'm not sure how the above grade foundation could be wrapped with 2" foil faced polyiso.
如果只是带有2个“ polyiso的乐队托梁，您可以使用〜6”的开放式牢房（最多可以在单个通行证中安全地应用），但不会将泥浆密封到持续时间可靠地基础。如果使用开放的细胞泡沫，则与基础接触的泡沫仍将在随着时间的推移而有潜在的水分积累和霜冻损伤分离。
不要劫持他的线程但由于op the path to energy upgrades. I was referring to the exterior wall/ band joist if it were wrapped with impermeable insulation (faced polyiso) on the exterior. As the band joist can wick moisture from the rocks/ blocks since they did not use capillary breaks back then. I was under the impression that a vapor open interior insulation should be used. I imagine you would want to control basement humidity levels?
Most fieldstone doesn't have anywhere near the wicking capacity of poured concrete or CMU, making capillary break is less critical. Quarried limestone might have that issue, but not granite or basalt, etc. Most field stone in Boston is low/no wicking igneous type rock.
只有箔纸面对泡沫，仅带有带座的外部（而不是基础），可以在内部使用2英寸的闭孔。大多数闭孔泡沫仍然超过0.5 perms @ 2” - 它不相同真正的蒸气屏障将是水分陷阱。
Basement humidity in the "-A" climate zones is almost always about summertime air leakage from the outdoors into a basement at or below the dew point of the outdoor air, and literally never about vapor permeance of the wall insulation. It can sometimes be related bulk water seepage through the walls, or from the soil to a slab that has no vapor barrier, but even that is rarely "the" reason for high indoor RH.
In Boston the subsoil temp (and often the slab temp, even in summer) is less than 55F, and the mean outdoor dew point over the summer is north of 60F. Stopping the outdoor air infiltration fixes the first 75% of the basement humidity problem, but it will still need some amount of mechanical dehumidification (or air conditioning) to manage it.
任何对内部的绝缘层都会使周边woof框架较冷，因此干燥潜力较小。我看不到这样的结构从瓦砾粉底上弄湿。我看到的是地表水管理不佳，例如飞溅的木材组件接近湿级。确保在进行此能源细节时，您正在管理内外的水分负荷。
彼得