答复

1. 
   Jon R.|Sep 30, 2019 10:33am|#1

   Your plan is for an unvented/conditioned attic or a vented/unconditioned attic? Unless you have ducts up there, I suggest the latter - all insulation on the floor.

2. 
   Brian Pontolilo|Sep 30, 2019 10:47am|#2

   嗨,约翰。

   随着JON R提到的，方法 - 绝缘屋顶线VS绝缘阁楼楼 - 非常不同。绝缘屋顶线（通风或不透过）将阁楼带入房屋的条件空间。绝缘阁楼楼层在条件空间外保持阁楼（冬季冷，夏季热）。

   在您所在的位置，R-49是国际住宅代码希望在您的阁楼或屋顶上看到的内容。大多数高性能的建造者拍摄高于此。由于不经常的绝缘屋顶是一个风险化的组装，并且在许多方面更昂贵的封闭电池喷雾泡沫，我认为在纤维绝缘体中的打击绝缘阁楼地板是更好的路径。当然，在做一些真正勤奋的空气密封之后。我假设你已经看到了这些文章，但如果你没有，请退房：

   How to Build an Insulated Cathedral Ceiling
   创造一个有条件的阁楼
   空气密封阁楼
   How to Insulate an attic floor

3. 
   John Chard.|2019年9月30日11:24 AM|#3

   Thanks Jon and Brian.

   I forgot to mention. Our second floor mini split will be ducted and the air handler and duct work will be up there. Its an old attic with a flimsy timber door and narrow stair case. The attic floor does have cellulose blown in. The efficiency contractors from Eversource have tried some simple weather stripping. This will be our first winter here and I worry it will be like a fridge with a plywood door!

   So given this and the ductwork, I thought foaming it would make sense to at least make it airtight?!

4. Expert Member
   Dana Dorsett|2019年9月30日01:11 PM|#4

   It can sometimes even be cheaper to build an air sealed utility-chase/platform over the mini-duct cassette & ducted region and install R49 above the platform than to put R49 at the roof deck. Installing short ducts to ceiling diffusers at the interior side of the rooms with ceiling diffusers designed to throw air toward the exterior walls/windows can keep the size of that platformed area small. An insulated weatherstripped hatch or door to the utility chase under the hatch can provide service access. That approach would require air dams in every joist bay that crosses under the mini-wall of the chamber.

   由于它不是结构（它只是阻止绝缘，而不是天花板，而不是屋顶），它都可以用2x4框架和密封的半英寸OSB在框架的外侧。

   Some thought has to be given to the return path ducting. A common return grille in a section of ceiling (perhaps set up for swapping the filter media without going into the attic) using partition wall cavities as jump ducts to the common areas can usually work. With a grille into the partition stud bay near the floor in the doored-off room and near the ceiling on the common space side of the walls provides better sound & light isolation than door cuts at the threshold, and better mixing than transom grilles or jump ducts penetrating the ceiling.

1. 
   John Chard.|Oct 01, 2019 10:22pm|#5

   谢谢达娜。我们有一个有点尴尬的小空间，以及超级旧台阶上的最具魅力的阁楼。

   So what I am hearing is-
   1. No ductwork, then R49 the floor
   2. Ductwork, then I could create an air sealed utility chase with R49 outside (ie a room within the room) or I foam and seal the roof deck at 4" at

   Is this right? Is there an option where its roofline PLUS attic floor?

   谢谢，

   John