答复

1. GBA Editor
   马丁·霍拉迪（Martin Holladay）|Jun 07, 2017 05:00am|#1

   Paul,
   If you want to re-roof an old roof with existing board sheathing and existing asphalt shingles, the first step is to strip off the old shingles and inspect the boards. If the boards are sound, and the gaps aren't too bad, you can certainly reuse the boards -- perhaps after re-nailing some of them.

   Homes with a vented unconditioned attic don't need airtight roof sheathing. But in your case, you are planning to have an insulated sloped roof assembly (rather than a roof over a vented attic) -- an assembly that requires a tight air barrier at the sheathing layer. In theory, you could create this air barrier by installing a taped European membrane, synthetic roofing underlayment with taped seams, or a layer of OSB or plywood sheathing with taped seams.

   I think that it makes the most sense to install new plywood or OSB over the boards, taping the seams of the new sheathing, because you'll end up with a more durable air barrier and a nice new surface to work on.

   这种新的护套层与板的状况无关。这只是一个耐用的空气障碍。这种方法比试图在旧板上安装欧洲膜或合成屋顶底层更有意义，并希望该膜足够耐用，可以成为您的空气屏障。

2. 
   Steve Knapp CZ 3A Georgia|Jun 07, 2017 07:46am|#2

   马丁，

   看来保罗正在计划一个金属屋顶。对于他的气候，使用钉子来创建冷屋顶组件是否有意义？

3. GBA Editor
   马丁·霍拉迪（Martin Holladay）|Jun 07, 2017 07:59am|#3

   史蒂夫，
   As my article on this topic (How to Build an Insulated Cathedral Ceiling) explains, there are a great many ways to detail a sloped insulated roof assembly.

   The assembly can be vented or unvented.

   如果需要，组件可以包括屋顶护套上方的刚性泡沫，也可以在没有任何刚性泡沫的情况下建造。

   If the builder wants to use rigid foam, it's possible to install ordinary rigid foam (perhaps recycled foam), and it's also possible to use nailbase.

   If you use nailbase, you can choose unventilated nailbase, or nailbase with a ventilation channel built right in.

   All of these options, including the nailbase option, are mentioned in my article,How to Build an Insulated Cathedral Ceiling.

4. 
   Paul McKevitt|2017年6月7日08:34 AM|#4

   感谢马丁，这很有意义。

   我意识到我还有另一个屋顶问题，希望您能照亮一些。

   There is a small "bump-out" (8' x 14") with low slope shed roof attached to the side of the cabin, which I was planning on just insulating with the rigid foam (vented same as on Gable roof) on the outside only and no insulation on the inside which would leave the existing rough pine roof boards exposed (rustic look).

   My problem is that unlike the insulated walls, I can't air seal that roof section on the inside because of the exposed boards and rafters. Is there any other way of sealing it, maybe from the outside before I put down the new roofing material?

   谢谢，
   Paul

5. GBA Editor
   马丁·霍拉迪（Martin Holladay）|Jun 07, 2017 08:58am|#5

   Paul,
   答案可以在我的答案＃1中找到：“您可以通过安装带有胶带接缝的胶带，合成的屋顶衬里或用胶带接缝来创建此空气屏障。”我没有提到它，但是如果您愿意，您可以使用果皮和水上盾等剥皮产品（尽管有些绿色建筑商担心皮肤和粘性产品可能会有令人反感的气味）。

   For more information, see this article:How to Install Rigid Foam On Top of Roof Sheathing.

6. 
   Paul McKevitt|2017年6月7日09:34 AM|#6

   感谢马丁。

   我了解您在山墙屋顶上的答案，山墙屋顶上密封在内墙和大教堂的天花板上，但我想我的担心是在屋顶的“颠簸”部分的内部没有膜或空气密封，可能是让温暖的空气通过裸露的屋顶板升起。

   So as long as I do the air seal on the exterior of this section as you described , I should be good?

7. GBA Editor
   马丁·霍拉迪（Martin Holladay）|Jun 07, 2017 09:43am|#7

   Paul,
   任何空气屏障都需要连续。我描述的材料将有效，但是当然，您的天花板空气屏障需要连接到墙壁屏障。如果您在墙/天花板交叉路口有裂缝或泄漏，则所有赌注都关闭了 - 无论您选择哪种类型的天花板空气屏障。

8. 
   Paul McKevitt|Jun 07, 2017 10:46am|#8

   Got it.

   再次感谢马丁