Remodel – Insulating a permanent wood foundation (PWF)
背景
我们最近购买了建在永久木基础（PWF）之上的木屋。这是一种牧场风格（26’x47'）单层。建于1980年。我们已经完全掩盖了地下室。我们一直到PWF中心1英尺的2×6螺柱墙。以前，房屋是通过燃木炉和电动踢脚板的热量加热的，这些炉子都被除去。我们使用了用于燃木炉的管道工程的地理热量。这是由水炉制造的地面源热泵（5系列）。
When we gutted the basement, the walls had wood paneling on top of the sheetrock. The sheetrock was not taped or mudded. Behind the sheetrock was a vapor barrier that was stapled to the studs and the stud cavities had unfaced batt insulation. When removing the batt insulation we could feel it was a little damp near the bottom in a few spots. The batt insulation filled the cavity and there was no gap behind it, or at the bottom. The batt insulation was in contact with the concrete because the concrete was poured over the bottom plate. There wasn’t any mold. The basement did have a very slight damp/musty smell to it. The carpet and pad was installed directly on the concrete which may have been the culprit for the damp smell.
唯一一次我看到水在地下室when we had a heavy rainstorm come through in the early spring and the frost had not let up out of the ground yet. Water was coming in through the wood sheeting on the PWF in a few spots and pooling in the bottom of the stud cavities. Which reminds me, the soil where the house is built is all sand. When they dug the 300′ trench for the geo, it was all sand. That trench was 8′ deep, and 8′ wide.
我们在威斯康星州欧克莱尔（Eau Claire）的气候6A地区。在我的问题上...
We were considering spray foam insulation but it is extremely expensive and we are concerned about the breath-ability of the walls. I have ordered and gone through Joe Lstiburek’s book, “Builder’s Guide to Cold Climates” where he states that the wood wall is warm and will dry to the interior. The book shows how to assemble a wall on new construction and has the rigid insulation on the exterior. I like the idea of the rigid insulation on the exterior… but I’m curious if I would have to install it ALL the down to the footing, or if it could be installed from the top plate to 16-18″ below grade? Then on top of that… how could I make the transition from the logs to the rigid insulation as the rigid insulation will now be sticking out three inches? As I stated in the beginning, it’s a log home, with full logs. So, I can’t carry the rigid insulation all the way up to the roof line. Also, how would you retrofit the rigid insulation around existing penetrations (water faucets, electrical service coming in, windows, etc)?
OR… do I just follow the 2015 American Wood Council (AWC) guidelines for PWF and insulating on page 15?http://www.awc.org/pdf/codes-standards/publications/pwf/AWC-PWF2015-Commentary-ViewOnly-1411.pdfAs I type this out and think about it, I’m leaning towards the AWC guidelines because super sealing and insulating the basement isn’t going to “make-up” for the insulating values of the logs. Also, the previous batt insulation was there for 36 years and there wasn’t mold… so, it works. If I go this route, I will just have to spend some time insulating the rim joists with rigid insulation and Great Stuff spray foam..
寻找一些指导 /建议。我不怕挖掘和做这项工作。我只想做一次。我的孩子们那里会有两间卧室。我希望他们很舒服。
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Jeep,
If your basement gets water entry after a heavy rainstorm in the early spring -- "Water was coming in through the wood sheeting on the PWF in a few spots and pooling in the bottom of the stud cavities" -- then it's not a good candidate to be converted to finished space ("two bedrooms down there for my kids"). Before finishing these rooms, you absolutely have to solve the water entry problem.
这可能需要重新分级，防水，固定下台或更改回填材料。但是，无论您做什么，都需要在将卧室放在那里之前解决入口问题。有关这些问题的更多信息，请参阅固定湿地下室。
Q. "We were considering spray foam insulation but it is extremely expensive and we are concerned about the breath-ability of the walls. I have ordered and gone through Joe Lstiburek's book,寒冷气候施工指南,他说,木头墙是温暖和will dry to the interior. The book shows how to assemble a wall on new construction and has the rigid insulation on the exterior. I like the idea of the rigid insulation on the exterior, but I'm curious if I would have to install it ALL the down to the footing, or if it could be installed from the top plate to 16-18 inches below grade?"
A. The best way to insulate your basement walls is definitely to install rigid foam on the exterior of the walls. The second-best way to insulate your basement wall is with closed-cell spray polyurethane foam on the interior side. Ideally, the insulation would extend down to the footing. But if your budget doesn't allow full insulation, the part of the wall where insulation is most needed is the top half of the wall.
Q. "How could I make the transition from the logs to the rigid insulation as the rigid insulation will now be sticking out three inches?"
答：刚性泡沫的顶部（在建筑物的外部）需要用金属Z刷子完成。应尽可能靠近底部日志。您需要尽最大努力在底部日志以下的裂缝中滑动一些金属，并在Z刷的顶部将金属闪烁的膝盖闪烁。
Q. "How would you retrofit the rigid insulation around existing penetrations (water faucets, electrical service coming in, windows, etc)?"
答：需要重新定位水龙头（霜冻底库），或者需要重新定位现有的sillcocks或现有的Sillcocks。电气服务的渗透需要闪烁。窗户将需要外部JAMB扩展名和新的外侧窗台。
Q. "Or do I just follow the 2015 American Wood Council (AWC) guidelines for PWF and insulating on page 15?http://www.awc.org/pdf/codes-standards/publications/pwf/AWC-PWF2015-Comm。当我输入此内容并考虑一下时，我倾向于AWC指南，因为超级密封和绝缘地下室不会为原木的绝缘值“化妆”。
A. The choice is yours. The AWC guidelines aren't based on building science. These guidelines are a compromise. The guidelines were developed in hopes of promoting wood foundations without incurring high expense. As you noted, "When removing the batt insulation we could feel it was a little damp near the bottom in a few spots." This type of dampness may not matter for an unfinished basement, but it's not a good idea for a bedroom.
考虑到（a）您的地下室偶尔会经历水的事实，以及（b）强大的防水和绝缘溶液的昂贵事实，您可以得出结论，地下室的最佳用途是作为容纳机械设备的地方。为您寻求的两间卧室建造高级增加可能更便宜，更容易。
I respectfully disagree with Martin, who is openly hostile to PWF! How can he justify the assertions about the origin of the guidelines and their lack of basis in building science, was he involved in their generation, has he even talked to anyone who was? The best way to insulate your basement is NOT exterior foam! I do however agree that the water leaks absolutely must e fixed FIRST. The exterior poly water barrier (it should be at least 6 mil poly from 8" above grade to the granular footings) needs to be "restored" and the site grading and water runoff fixed so it follows the guidelines you obviously have. It may (probably not) also take replacing some of the backfill with free draining material. But the best way to insulate, after addressing the water problem is to follow the PWF guidelines, especially the 2" gap a above the bottom plate, it is there to allow draining of any water that does get into the cavities without wicking onto interior finish materials. Either fiberglass or my preference mineral wool bats will work well. The performance of the insulation will be degraded unless you achieve a good air barrier with whatever interior finish material you use. In other words, the drywall should be air tight.. Even without an air barrier moisture in the insulation or condensation are NOT issues, the design is based on wet wood which will dry out if there is proper drainage. DON'T waste good money on spray foam! Your problem was clearly caused by the builder NOT following the guidelines about the 2" gap at the bottom, fix that and correct the other "mistakes" and you'll have a warm dry energy efficient green basement, far superior to concrete!. FWIW I'm presently in the process of building a PWF basement and have talked to more than one of the authors of the guidelines.
Jerry,
I stand by my recommendations. When warm, humid interior air contacts cold plywood, the result is condensation. Fibrous insulation does not prevent the humid indoor air from contacting the cold plywood. That's why exterior rigid foam is a good idea: it raises the temperature of the plywood to reduce the chance of condensation.
Martin,
And as the proverb says" it the dog hadn't a stopped to take a dumo he'd a eaten the wabbit"
有了合理的内部空气屏障，不会有任何温暖的潮湿空气，那里有什么温暖的空气将具有外部空气的露点，而且永远不会凝结。上述指南显示Poly（可能不再是最佳选择）作为内部空气屏障。无论如何，木材结构被设计为湿，因此冷凝不造成伤害，最终会干燥/排水（由于凝结将首先发生在绝缘材料中，排水量更大）。在PWF指南中的2英寸差距中。好吧，我终于从该指南的一位作者那里找到了答案，正如我所说的那样，它是为了防止芯吸和允许将任何冷凝物滴入排水条款中。提倡外部泡沫。PWF无非是一种公然的尝试，即在混凝土上消除PWF的明显优势（低成本绝缘）。PWF与混凝土浴缸中的内部木壁有所不同，该排水液可用于任何冷凝物，在任何情况下都不是这种情况。混凝土浴缸。
删除
Jeepasarus.
Spray foam 3 inches deep inside cavities 12" OC assuming that it really is r21 only results in an r 12 wall because the thermal path through the studs is only 3 inches. Five and a half inches of mineral wool is also r21 or more but because an additional two and a half inches of stud is the thermal path results in r 15. The lower cost of mineral wool will at least partially pay for a quality interior air barrier and that's were it quits being economically wise, as you have said you have other places to reduce heat loss with better cost/benefit ratios.
Thank you for the links! The Connecticut story sure debunks the myth that concrete is forever!
The actual limit of the life of a PWF is truly unknown but they sure don't crumble even when mistakes were made. The only known degradation is due to fastener corrosion and if the guide was followed those effects are at least 500 years away.
Jerry: The CT crumbling concrete is strictly a rare inappropriate aggregate material issue- the exception that proves the rule. Barring that sort of problem concrete may still not be forever, but long enough from a human or US home lifecycle point of view.
For the ~20,000 homes affected it's a real PITA to fix, but still not always an irretrievable disaster unless it's allowed to go for too long. Hard strapped home-buyers without the means to fix the affected house are facing a financial disaster though (and their lenders are potentially taking a serious hit.)
去年，我参与了在法明顿康涅狄格州的一所房子，房主担心这是“其中一栋”房屋，但值得庆幸的是，该房屋的症状归因于其他较便宜的事情要解决的问题，而基金会看起来不错。这所房子是正确的年份，没有关于混凝土来源的记录，但是尽管有一些小小的沉降，但粉底墙和平板的状态非常好。
在您阻止水问题之前，我看不出如何宜居。这样做的唯一真正的方法是将外围挖掘到页脚上，一旦您到那时，为什么不将外部隔热呢？
删除
Its your call, but I wouldn't be comfortable with anything less than digging down to the footer, and properly waterproofing the out side with a drain layer, gravel, fabric, and a french drain to daylight. wood+water=rot and mold no matter what the supposed claimed life is...
我看过PTL柱腐烂和不锈钢腐蚀
删除
Jeepasaurus,
Most people, particularly homeowners building fences, don't make the distinction between the types of PT wood that are available, and don't use ground-contact rated PT when they should. Hopefully most builders that use wood foundations, and have to go through an approval process, can be assumed to have used the right PT lumber