Roof replacement and insulation
I plan to replace my roof shortly. I am in zone 2A. Roof is 1″ in 12″, so low slope, and about 24 squares. House looks like an Eichler sort of, but not as nice. Only has 5 penetrations so roofing should be relatively easy. Current assembly from outside to inside-
火炬向下钻头，屋顶毛毡，5/8“胶合板，2 1/2”x 6 1/2“光束4”在中心，箔片，2x4s绑在梁的底部，干墙。一些天花板有6英寸的贝蒂，安装不良。
壳体是砖，气隙，外部石膏板，2×4壁螺柱。在砖墙的顶部，有木壁板约12英寸到屋顶甲板。这侧面有2个“孔”，即将托托湾隆入通风口。
I plan to leave the existing roof, add 3″(maybe a little more) of polyiso, then maybe a recover board, then 80 mil TPO.
在轮辋托珥床上打开屋顶是否值得（不确定这组件是否正确的术语），并将短区域从墙壁顶部到屋顶甲板上的泡沫？这将密封那些通风孔，并给我一些靠近绝缘和密封的信封的东西。
Comments and options are appreciated.
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Replies
User-6925549,
First of all, can you tell us your name? (I'm Martin.)
Q. "Is it worthwhile to cut the roof open at the rim joist (not sure if that is the correct term for this assembly?) and spray foam that short area from top of the walls to the roof deck? That would seal those vent holes and give me something close to an insulated and sealed envelope."
A. Yes, that would be worthwhile.
Q. "Comments and options are appreciated."
A.三英寸的Polyiso为您提供R-18或R-19。在您的气候区，建设代码最低限度的R-38，这是计划的两倍。所以我敦促你考虑安装6英寸的Polyiso。
For more information, see“绝缘低矮的住宅屋顶。”
U-Factor基础上的Code Min是U0.030，或R33.3“整个组装R”。适用于可操纵的火炬屋顶的屋顶Polyiso通常是R17 @ 3“。内部和外部空气薄膜添加另一个R1，屋顶甲板和干墙加入另一个R1，所以现在您在R19。
为了加入额外的空气薄膜和纸铝的反射率的合法可以加入最高的R8-R9当闪亮 - 新的干燥时，但甚至脱脂涂层冷凝（你空调房子，你，带来铝的温度下降到室外露点）有时会降至〜R3，如R3所以最差的套件，你真的在R22，而不是R33.3。
阻挡通风口并吹过的箔上方的空间充满了1LB密度玻璃纤维的空间将在中心腔处产生另一个R24，甚至在对热桥接中的考虑后肯定会足够。在屋顶甲板上方有R17，您可以获得超过足够的露水点控制在屋顶甲板上。
无论是6英寸的Polyiso还是3“Polyiso + 6.5”绒毛，问题仍然是底部加上TPO在顶部的TPO留下的箔片仍然产生水分陷阱，一旦通风口关闭就会产生水分陷阱。我相信它确实如此。如果它可能删除在填充腔之前至少大部分箔将是更加湿度的弹性。
在垂直砂浆中的垂直砂浆中向外部向外部通风，每18-24“在底部附近的砖头上，以及在顶部附近的砖路线中的相应通风口将对对流干燥的空间砖。有目的地制作的错误屏幕，T楔入哭泣和通风口。
Thanks for the replies.
I am David.
I will try to edit my user information and have my name appear.
Martin,
2 issues with meeting code-
1)Doubling the foam thickness is going to add some dollars, I will get that cost from the roofer.
2)The face of the eave is currently 9 3/4" thick. Adding 3" is going to start looking too thick, adding another 3" to that will likely look bad. I realize these are aesthetic issues but that does factor in for re-sale and such. However, I will mock up a section with 6" of added thickness and see how it looks.
达娜，
我认为填充绝缘体吹的床湾太难以/昂贵。如果我正在删除和更换所有的装饰，我会考虑添加击球或吹入。但这将是太昂贵的。我也关注你提到的水分问题。当然，如果我重新装饰，可以容易地取出箔片。
I like the idea of venting the bricks. It seems like a DIY project I can handle. I will search for some tips on the procedure.
I reckon this project is like many others and has to be balanced between cost, effort, and return. Going from essentially no R value to R-18 is probably the best I can manage but I will consider options.
The moisture trap problem issue exists whether or not the bays are insulated with fiber, or whether there's 3" of foam up top or 6". It was designed to be vented from below, which is a thermal bypass for the insulation, but gives an air-drying path to the outdoors. With the foil in there preventing drying via diffusion to the indoors it's a moisture trap once the vents are blocked. That's fine if the wood is dry when it's sealed up, provided the roof never leaks.
Using reclaimed roofing foam 6" is cheaper (and greener) than 3" of virgin-stock polyiso. Many building supply salvage outfits will have it, many will advertise in the local craigslist:
https://houston.craigslist.org/search/sss?query=rigid adksfoam.
https://neworleans.craigslist.org/search/sss?query=rigid +foam.
https://jackson.cregslist.org/search/sss?query=rigid adksfoam.
https://montgomery.craigslist.org/search/sss?query=rigid+foam
https://jacksonville.craigslist.org/search/sss?query=rigid+foam