Double stud walls & wood shrinkage
我在密歇根州北部的新房子的不断发展计划使用双螺柱墙。外墙坐在混凝土基底壁上，而内壁坐在地板上坐在地下室的内螺柱壁上。地下室的内螺柱壁与XPS的混凝土分开。外螺柱壁支撑屋顶桁架。内部主地板支柱壁在其外侧护套，这种护套是主要空气屏障的垂直部分。外螺柱壁支撑屋顶桁架。如果我试图使用桁架的下部和弦作为天花板空中障碍，我会发现一个问题。内壁几乎是高度的两倍，并且与外壁相比，横粒压缩的木材更大，因此即使两个壁都同样干燥，内部也会缩小远远超过外部导致在壁上空气密封的任何尝试失效天花板。这是一个有效的问题吗？ My best solution is to NOT use the lower chords of the trusses to form the ceiling but add ceiling joists supported by the inner wall and interior partitions. I would put OSB on top of the ceiling joist and detail that as the ceiling air barrier (caulked to the inner wall sheathing) and have the lower chord of the trusses above that, of course this means my outer walls will need to be taller & the OSB above the ceiling joist may as well continue outward to tie the walls together. Before addressing the shrinkage issue I had planned on sheathing the bottom chords of the trusses with OSB to form the top of a service cavity then ‘hanging’ 2×4’s below that to support drywall. Going to 2×8 ceiling joist sheathed above before the trusses is more conventional, probably less labor but more lumber but it does allow can lights inside the air barrier. Am I right that it eliminates any concern over differential shrinkage of inner & outer walls?
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Hi Jerry,
我比言语更加视觉
It is difficult for me to follow your description.
你能发帖吗？
Since you are concerned about differential shrinkage....
check out figure 3 in this BSC Insight
http://www.buildingscience.com/documents/insights/bsi-023-wood-is-good-but-strange/files/bsi-023_wood_is_good.pdf.
约翰，
谢谢你的一个很好的参考。这个问题is much smaller than I thought because I'm using an ISL rim board and 'Trimjoist' which are more dimensionally stable than cross grain wood. But the article mentioned truss bottom chord uplift which can cause a similar problem. I still favor the redundant ceiling joist as it is much easier to construct and allows the can lights the wife wants. After reading the article I'm much less concerned about the ability to achieve a lasting air seal around windows and doors as gaskets should easily accommodate the movements. BTW my scanned wall cross section sketch is to big to upload.
Jerry,
您还在项目的规划阶段吗？
如果是这样，您可能有兴趣查看我发布在我的一些详细信息博客。
我也摔跤了你提到的一些问题......
我发现将所有承载结构保持在内部（内部框架）然后之后将所有承载轴承结构保持非常方便。
This way the sheathing is very easy to "connect" from wall to ceiling.
A drawback to this approach is that it requires an interior service cavity...
虽然John Brooks建议，也许干墙可以直接应用于胶合板护套（SANS服务腔）......
I haven't explored that idea much yet, but I may experiment with down the road...
If your scan is too big
和....你有一个PC .....
开始菜单
所有程序
Accessories Folder
Snipping Tool
很容易从屏幕上“剪掉”图像
它将被保存为非如此大的JPG
杰瑞：你是如何照顾任何坐在混凝土上的木材？垫圈之间？经过治疗的木材？您也许想搜索Sunrise House（Home？）Thorsten Chlupp已经建造和发布了这里的照片。听起来你有相似之处。
约翰，
Over concrete I'll have a closed cell foam (blend of EDPM,Neoprene and SBR) gasket and use a pressure treated plate. The gasket is a capillary break, the PT is a code requirement.
I was unfamiliar with ; 'Sunrise House' and am frankly flattered that you see similarities, I see some too, especially now that I've added the ceiling joist. Interestingly Thorsten strongly advocates locating windows near the center of thick walls which I'm planning for a very different reason. I plan on using 'thin brick' as exterior cladding and wanted recessed windows to mimic the "look" of conventional masonry veneer so my windows are essentially in the middle of my walls. Other than my much more modest insulation, r80 ceiling, r40+ walls, r25 basement, r10 slab, the biggest difference is that I use the outer exterior wall to bear the roof and set it on the concrete basement wall and I build basement stud walls to support everything but the outside wall and roof.. Also I gave up on solar thermal as an economical heating source and opted for PV and air source heat pump instead. But I will use a condensing vent less clothes dryer.