在不明的屋顶上的蒸气屏障......
User-7125415|Posted inEnergy Efficiency and Durabilityon
首先......什么伟大的资源。谢谢你。
我在洛杉矶北方的3个b / c区。热干燥。我有一个直线山墙屋顶线的部分大教堂天花板。施工大会要有：
Structural rafters (exposed)
2×6 T＆G护套
两种课程的聚类刚性（R-19）最多是指甲基础
Peel and Stick (Grace)
站立缝金属屋顶
在“如何在护套顶部安装刚性绝缘”的文章中，建议在结构护套上方/上方施加蒸汽屏障。我的案子里的t＆g。当与我当地建筑官员讨论这一点时，实际上是计划审查工程师，他告诉我不要在这里放一个蒸气屏障，而是让刚性保温密封它。
I suppose my question is….Is it detrimental to install a VB at the structural sheathing level ?
Thank you for any opinions.
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答复
用户-7125415，
首先，你能告诉你用你的名字吗？（我是马丁。）
问：“在文章中“如何在护套顶部安装刚性绝缘，'建议在结构护套上方/上方施加蒸汽屏障。“
答：这不是真的。该文章建议在该位置的空中屏障，而不是蒸汽屏障。
没有要求内部蒸汽巴尔ier in your climate zone. That said, if your polyisocyanurate is faced with foil, you already have a vapor barrier, whether you need one or not.
Concerning the need for an air barrier (which you didn't ask about): It's possible to use the polyiso as your air barrier, as long as the seams are carefully taped, and the two layers are installed with staggered seams. That said, rigid foam can shrink, and may even shrink away from the tape after a few years. So the best practice would be to install an air barrier between the tongue-and-groove sheathing and the bottom of the rigid foam, as described in my article. The article notes, "If your roof has board sheathing, install an airtight membrane (for example, Solitex Mento, a product available from 475 High Performance Building Supply), a layer of synthetic roofing underlayment, or a peel-and-stick membrane."
随着T＆G暴露于内部空间，它基本上在室内，在外侧有一个蒸汽屏障，并不是它的蒸汽迟滞在您所提出的堆叠和位置特别相关。
但需要改变堆叠，将剥离的“n”粘贴在极大的漏极下的t＆g上，而不是在钉子面板（这不是结构护套上方。）使用常设接缝制造商的屋顶推荐的界面。
With t & g decking a self-healing membrane such as Ice & Water Shield is the right way to go for better long-term air tightness. As Martin points out, foam expands/contracts with temperature and humidity, and even with the seams taped won't be nearly as tight as a self healing membrane or broad-sheet underlayment air barrier between the foam and the t & g.
即使没有箔面，也是一层纤维面对R19 Polyiso，你将非常接近真正的蒸汽屏障，在第II类蒸汽迟滞的非常紧密的末端。但是，您仍然不希望室内空气能够通过T＆G，并进入Polyiso床单之间的微观空间，以“较大的户外”及更远。
嗨马丁......
谢谢你的立即回复。再次......多么伟大的资源。人们多久可以从事信息技术文章的作者？
我担心我在这里是我自己的受害者。我遭受了不小心的阅读。你当然是正确的。空气和蒸汽之间的区别逃脱了我......他们只是我们的两个原则元素。
为了我自己的进一步的Edification，我们关注空气损失，因为它可能会带来蒸汽，还是仅用于热损失。
再次感谢，
Coleman
科尔曼，
Q. "Are we concerned with air loss because it may carry vapor with it, or simply for thermal loss?"
A. For both reasons. Attention to airtightness is a fundamental principle of green building, or any building attempting to comply with building science principles. For more information, see these two articles:
“关于空袭的问题和答案”
“压力诊断介绍”
感谢Dana，进一步扩展。这是非常有帮助的。
和马丁的响应和链接。
关于Q＆A讨论格式的伟大事物之一是可以解决在基本级别的理解的障碍....鼓励进一步发展......至少为我。
最佳 - 科尔曼