High R-value and WRB
我们有一个在70年代建造的房屋。据我们的估计，墙壁，OSB，建筑纸和顶部的带状疱疹可能有R7。我们想脱下当前的壁板并添加其他绝缘材料。
Our main concern is lower energy bills and comfort. Due to esthetics (windows already set) we cannot go higher than 1 inch (or so everybody says), so polyiso would make most sense in order to add the highest R-value. If we use it as a water drainage plane, the vapor barrier would have to go on the outside but wouldn’t that render its vapor retarder function useless?
For housewraps, most recommendations are of at least 3/8 inch drainage/ air flow space so putting it on the OSB then adding the rigid foam boards and leaving that drainage space seems ineffective since cold air will still get close to the OSB/ interior walls.
The house is located in zone 4, NY. Does polyiso with the foil side attached to the OSB, followed by housewrap (maybe ThermaWrap by Tyvek) and vinyl siding make sense for our climate? None of the contractors we talked to had this suggestion. A few of them also recommended the siding shaped foam (“insulated siding”), but again where would the water drainage plane be in that case and would there be any advantages to using it?
Any advice of how we can get a high R-value on the exterior and have good water management is welcomed. Thank you!
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Replies
L.S.，
Q. "Polyiso would make most sense in order to add the highest R-value. If we use it as a water drainage plane, the vapor barrier would have to go on the outside but wouldn’t that render its vapor retarder function useless?"
答：每堵墙都需要防水障碍（WRB）。但是，这与蒸气屏障不同。大多数（但不是全部）WRB都是蒸发的。
大多数墙壁不需要蒸气屏障。但是，在寒冷的气候下，蒸气延迟器很有用。蒸气延迟器安装在墙壁的内部，而不是外部。
It is possible to use taped foil-faced polyisocyanurate foam as a WRB. It is also possible to use housewrap as a WRB. If you use housewrap as a WRB on a wall with OSB and polyiso, the housewrap can go under the polyiso or over the polyiso -- your choice.
问：“对于房屋包装，大多数建议至少为3/8英寸的排水/空气流动空间。”
A. You are describing the functions of a rainscreen or drainage gap. The rainscreen or drainage gap can be adjacent to the WRB, but it doesn't have to be.
Q. "The house is located in zone 4, NY. Does polyiso with the foil side attached to the OSB, followed by house wrap (maybe ThermaWrap by Tyvek) and vinyl siding make sense for our climate?"
A. You could do it that way. I think it's better to put the housewrap on top of the OSB, followed by taped polyiso, followed by vertical rainscreen strapping, followed by siding.
Q. "A few of them also recommended the siding shaped foam ('insulated siding'), but again where would the water drainage plane be in that case and would there be any advantages to using it?"
答：并非所有墙壁都有排水间隙。如果您可以创建一个，这是一个好主意，但这不是必不可少的。使用绝缘壁板的优点是减少泡沫 +壁板的厚度。
Thank you very much for the quick response! I had imagined a water barrier needs always a drainage gap adjacent to it which was complicating things!