答复

1. 
   Steve Knapp CZ 3A Georgia|9月20日，2021年05:08 pm|#1

   BD,

   I think this may be one of those designs were you want to use closed cell foam or a combination of closed cell and air permeable insulation. Just may sure your rafters are deep enough to install the amount of insulation you will need.

2. Expert Member
   阿科斯|Sep 20, 2021 09:14pm|#2

   If your budget is tight, the first to cut is the 5.5" of closed cell foam (btw, most installers don't do 5.5", the most you'll get is 5" since it is very hard to trim flat). The 5" of cc SPF will give you impressive center of cavity R values, but because of the thermal bridging of your studs it barely budges the assembly R value.

   Assuming standard cladding plus drywall, the 5" of cc SPF+ZipR9 has an assembly works out around R28, same wall with R24 batts is and R26 assembly. Since you already need to tape ZipR, you don't need the air sealing ability of the SPF.

   The better use of the SPF is in your roof plus dormers as Steve suggests. Since you have a complicated roof with knee walls and dormers, this is really the best way to seal it up. This will also make the mini attics behind the knee walls a conditioned space so you can run your ducting there or use it for storage.

   如果您想节省一些额外的费用，只需将SPF运行到2楼的天花板。顶部的阁楼可以保持发泄，并搭配便宜的蓬松隔热材料。

   您可以将整个屋顶与蓬松和瓦特的结合结合在一起，但是由于有很多过渡，因此需要大量注意以确保空气屏障的连续性。

1. 
   bdhome|Sep 20, 2021 11:22pm|#4

   阿科斯, thank you.

   我不遵循R值的数学。5英寸CC SPF为6/in so = 30 + Zipr9 = 39。这应该接近40的目标，或者您是否会以某种方式考虑热桥？我的建筑商和建筑师从未做过外部绝缘材料，并且是谨慎的。

   我的建筑师和建筑科学顾问正在计划完整的无条件阁楼，并且没有通过它进行任何管道工作。他们说，通常在南部（我是气候6/7）进行的无通行阁楼，他们只是在纤维素中使用很多吹。鉴于我认为试图最大化CC SPF的窗户的局限性在这里很有帮助，但我不知道他们如何计划。

   转换担心我。我将also love to keep a continuous envelope and not have the eaves constantly cutting through where the walls meet the roofs, but my architect and builder are unsure about this. For the main roof, is it possible to have a continuous envelope with, say, a zip system that then cuts across halfway up the roof so the bottom half of the top story is all conditioned and the top half not?

   Thank you for your time.

   The

1. Expert Member
   阿科斯|9月20日，2021年11:57 pm|#6

   您可以在此处浏览一些汇编值：

   https://cwc.ca/design-tools/effective-r-calculator/

   They don't have all options, but you can see how things compare. Thermal bridging does really hurt when using closed cell inside walls. Even though you are installing ~R32 of spf, you are only getting an R19 assembly.

   这非常接近您的组件，但只有R7.2外部刚性。使用ZIP R9，只需添加额外的R1.8即可。

   http://effectiver.ca/calculator/wall.php?id=2440

   R40 walls make sense when you are using cheap and low embodied energy insulation such as cellulose. There is no ROI or CO2 benefit with an R40 SPF wall.

   Your 2x6+ZipR9 is a great wall. If you skip the SPF and go with batts, the only thing you need is an interior warm side vapor retarder. Going up to Zip R12 would let you skip the vapor retarder but this is much harder to install as it require a special framing nailer that can shoot 4" nails.

   My suggestion was to only go for an unvented assembly for the bottom half of the roof, only the section bellow the 2nd floor ceiling. You can carry the spray foam down along the roof and down to the top plate of the exterior walls to ensure air barrier continuity. You might need to staple some backing by the eves to contain the SPF if you have large truss members there.

   It is very important to get that area well sealed both your floor joist as well as truss members intersect, making it a very complicated area. Make sure the SPF installer pays attention there.

   在SPF进入并安装了2楼的天花板式蒸气屏障并修复任何空气泄漏之后，最好进行初步鼓风机测试。

3. 
   Jonny_H|9月20日，2021年09:25 pm|#3

   我不知道处理像这样的复杂屋顶的最佳方法 - 除了在设计阶段避免使用，但是那艘船已经航行 - 可能是无通风的组件是这里最安全的。不过，另一件事在您的帖子中对我很突出：

   >侧壁为2×6，闭孔5.5英寸，周围有连续的Zip-9护套。预算现在很紧张，任何选择都可以考虑成本。

   您肯定可以通过在墙壁上使用不同类型的绝缘材料来削减成本，而不会牺牲很多其他。闭孔泡沫的三个最大好处是每英寸的R值高，空气密封和蒸气不渗透性，但这些功能均以巨大的货币成本和高环境影响为代价。在您的墙壁中，由于螺柱的热桥，浪费了高的R值每英寸，而且由于ZIP-R，空气密封和蒸气不渗透性都是不必要的。（在您的屋顶组件中，需要 *的一层闭孔泡沫 *的蒸气质量是 *。/ - ;封闭电池泡沫可以让您进入R-34 +/-，但可能是成本4倍（您可以在此处使用汇编R-Values：https://www.ekotrope.com/r-value-calculator).

   EDIT: Looks like Akos posted just before me, with probably better assumptions on the actual achieved R-value in the walls. Another idea: Could you use some of the money saved by not using ccSPF in the walls to bump up to zip R-12, or change to regular sheathing plus continuous exterior foam?

1. 
   bdhome|9月20日，2021年11:24 pm|#5

   我想做R-12和/或外部绝缘材料，但我的建筑师和建筑师从未做到这一点，并且犹豫不决。我不知道那有多困难。

   Thank you for your time.