Attic Insulation with a Wood Shingle (Vented) Roof
Hi;
Saw this site form Dan Houlihan of HeatingHelp.
I have a 1917 home in Detroit, Mich that I am renovating. It has a American Thatch” or “Smurf” cedar shingle roof with an open stringer deck underneath. These must be vented on the underside to allow the shingles to dry. Currently there is no insulation. The floor that the roof encloses is livable space, but I will demo all of the plaster walls for insulation access. I have 8″ rafters
What to do for insulation? I need about an inch of free space under the deck. The foam plastic air barriers don’t make for a very good “base” for insulation, but I can’t leave the backside of batt insulation “raw”, I suspect dirt and moisture over time would deteriorate it.
任何好的建议，欢迎您的建议。现在的供暖费是一种耻辱。
谢谢，
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In zone 5a (Detroit) you can put rigid foam underneath ventilation gap and skip the interior side vapor retarder as long as the foam-R is 40% of the total-R (eg, R15 rock wool batt with R10 foam, or R30HD fiberglass + R20 foam.)
If you're planning on doing it mostly as fiber you can make the exterior side air-barrier out of cut'n'cobbled 1" unfaced EPS (which is still at least semi-vapor permeable) sealed to the rafters with can-foam, and use a "smart" vapor retarder on the interior side of the fiber.
How much total depth do you have to work with? (A picture from the interior side might be useful.)
BTW: The stucco siding may have issues if not sufficiently back-vented. Depending on how that wall was built you may need to take a similar approach to insulating the walls.
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The simple answer to your question is that you need to build a vented insulated roof assembly -- also known as a vented cathedral ceiling. You can use a commercial baffle like AcuVent to create the required ventilation gap between the top of your insulation and the underside of your skip sheathing; or you can use a site-built baffle. Option for materials to create the site-built baffle include thin plywood, stiff cardboard, or thin rigid foam.
For more information on these issues, seeHow to Build an Insulated Cathedral Ceiling.
Hi;
感谢到目前为止提供的好信息。我附上了屋顶木木瓦部分的照片；我的错误只是2x6结构（顶部的平坦屋顶是2x8，我的困惑）。我想从这种绝缘材料中获得最大的能力，比巴特材料更好地喷在挡板预成式上吗？
The walls are stucco over clay tile blocks, sort of an early cinder block. There is a1" gap between the block and the interior plaster walls. I was thinking of foam sealing the top and bottom of these walls to create a dead air space, in the basement and attic. I had an aborted infrared blower door audit (they concluded the attic situation would not give any real results), but the contractor did check the surface temperature of exterior versus interior walls, they were the same temperature (20 degrees outside).
感谢指导。
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