在外墙上有polyiso的托梁区域开放式喷雾泡沫？
约翰·贝尔|Posted inEnergy Efficiency and Durabilityon
From all the reading I have done, am I correct that I don’t want to use closed-cell and need to use open-cell spray foam in the band areas of floor joists of the basement to 1st and 1st to 2nd floor areas when I have used polyiso sheathing on the outside of the walls?
I believe that is correct because of the perm is so low for the polyiso and you don’t want to use another very low-perm product like closed-cell spray foam sandwiching the Zip wall sheathing. I’m just confirming if I read everything correctly.
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Replies
约翰，
您是正确的，尽管我不相信那些使用闭孔喷雾泡沫的人可能会遇到问题。该区域不应该有太多（如果有的话）侵入，并且喷雾泡沫（无论是开孔还是闭孔）提供的优势大大超过了任何风险。
It also depends on how MUCH closed cell foam. Up to about 2"/R12 it's vapor permeable enough for seasonal drying. For thicker closed cell apps Icynene has a water-blown 2lb foam product that's still about 1-perm @ 5"/R25, but SFAIK it's the only non-HFC 2lb foam available in the US (and you have to seek it out and be specific- Icynene also sells an HFC-blown closed cell product that's much lower-perm and somewhat higher-R.) At 1 perm you would still have PLENTY of drying capacity for the wood.
从绿色/绿色/最绿色的角度来看，HFC吹泡沫是一只真正的狗，其生命周期温室的足迹比高R时抵消了能量用途更高。开放的细胞泡沫和吹水的闭孔更加良性。
If going open-cell you still have to pay attention to the dew-point factors & exterior/interior R-ratios relevant to your climate.
@DANA
这是一个古老的线程，但我处于这种确切的情况，并试图做出一个好的决定。我有1.5英寸的Polyiso覆盖了轮辋板区域的外部，需要决定在10英寸倒入混凝土墙的14英寸TGI托梁之间的边缘托梁上的隔热材料。我在外部上有3英寸的XPS我的倒入墙壁，Polyiso在窗台板级别完美相遇。我知道我不想在轮辋板上使用闭孔，但是我怎么知道正确的深度以在该区域喷出开放式电池泡沫？我担心……我在47460区域代码中。
At 1-2" closed cell foam would not be a problem.
In zip 47460 you could just do 4-6" of open cell foam, but a flash-inch of closed cell + R15-R25 (or more) of dense fiber such as damp sprayed cellulose or rock wool batts would would be more protective of the rim joists due to the ~1 perm vapor retardency of the closed cell foam.
@DANA
您说即使在1“厚度下，也最好使用闭孔？，纯粹是从成本的角度看，开放的单元是一个更好的主意。...我有10英寸厚的墙壁，这样我就可以做4-6英寸的开放式牢房，并且在该区域仍然有空间供您使用。还是我可以让他们喷到整个腔体上充满开放的牢房？我认为最终将大约8英寸左右。我将窗台板固定回3/4英寸，以使我的1.5英寸polyiso在水上垫上与坡度以下的倒墙上的3英寸XPS对齐。
您对蒸气紧密度的印象似乎有点不合时宜。
虽然Polyiso的箔脸是TRU蒸汽屏障，但大多数2LB聚氨酯喷雾都在约0.8-1.5[email protected]1“。在2”仍然不比在瓦特上的牛皮脸更紧。
The foil facers on polyiso run about 0.05 perms (or less), that's a full order of magnitude tighter than 2" of 2lb spray polyurethane. So while 1- 2" of closed cell foam is tight enough to protect the band joist from wintertime moisture loading, it's sufficiently permeable for the band joist to dry toward the interior the other 8-9 months out of the year.
很封闭的泡沫细胞的共同使用1 - 2”on band joists with unfaced batts to fatten out the R on the interior.
@DANA
我的poyiso不面对箔纸吗？我在外部安装了玻璃纤维面向的多丽莎板。
So the 2" closed cell route is better than the thicker open cell route
@Dana
I was wondering if the fiberglass faced polyiso has different characteristics than the foil faced for PERM levels?
安东尼，
问：“我想知道玻璃纤维面polyiso是否具有与箔纸的特征不同？”
答：是的。面箔的聚异氰尿素是真正的蒸气屏障。正如达纳（Dana）所指出的那样，铝箔层的渗透率为0.05 pers或更少。玻璃纤维面的多丽丝将比箔面对的多丽丝更明显更可渗透。如果您想要有关任何特定产品的渗透率评级的更多信息，请与Polyiso制造商联系。
So, since there is such a higher vapor permeance with the fiberglass facing I should be fine with the 2" closed cell against the band board because I have a better capability of drying in either direction? Now I understand why Dana said that.
Unfaced polyiso runs anywhere from 1.5-3 perms @ 1", depending on density & manufacturer. Facers of lower permeance are usually added to lower the total vapor permeance, and limit the moisture uptake of the foam itself. (Polyiso is hygroscopic- it will take on moisture and drop in performance if chronically wetted by bulk moisture such as roof leaks.) Most fiberglass faced goods are less then 1 perm, but more than 0.5 perms typically characterized in the specifications as "less than 1 perm". Some manufacturers of "breathable" polyiso specify that the permeance will be greater than 1 perm, independent of thickness, but that would limit the thickness to 2-3", due to the inherent vapor retardency of the polyiso itself.
But even 0.5 perm fiber-faced polyiso offers 10x the drying rate of a single foil facer, and something like 20x the drying rate of 2 foil facers. With a half-perm or more of drying capacity to the exterior and (with 2" of ccSPF) half perm of drying capacity toward the interior moisture won't be permanently trapped in the band joist, and it will dry at a rate fast enough to avoid rot issues (even if it got rained on prior to insulating.)
谢谢达娜。
My house got rained on quite a bit before the siding was installed but it dried out nicely before we put the siding on, I don't expect I have any issues with the foam being saturated, I hope it didn't soak up to much from the rain it endured when it was exposed, i assume this happens quite often on homes with polysio on the exterior
@Dana
忘了提到，在这些乐队板/边缘托梁区域中，封闭牢房的成本并不是对开放式牢房的疯狂升级，您提到，封闭式牢房实际上比5-6英寸更安全的路线用我的polyiso打开细胞泡沫...因为我正在使用玻璃纤维面对的polyiso，这仍然是真的吗？
There is far less danger to the band joist (with either method) due to the fact that the polyiso is likely to be at least an order of magnitude higher permeance than foil faced goods.
47460年邮政编码为1.5”,0.5 - 1烫polyisoon the exterior you'll be fine using 5-6" of open cell foam on the interior side, but it's worth spraying the interior surface of the open cell foam with "vapor barrier latex". That will reduce the vapor permeance of the foam layer to about 5 perms (instead of 10+), making it comparable to a standard latex paint on gypsum. (Vapor barrier latex on paper-faced gypsum runs about 0.5 perms, but is far more permeable when applied to open cell foam.)
An open cell solution would be preferable to 2-3" of closed cell foam for a couple of reasons. The deeper foam depth means the thermal bridging of the I-joists is cut by half or more, the drying capacity for the band joist is higher, and the substantial environmental damage from the HFC blowing agents used for close cell foam is avoided completely.
Outstanding! Open cell it is. Thanks a ton.