在阁楼afters下方移动喷雾泡沫绝缘
Hello, My name is Shawn. First off, I apologize for perhaps the millionth attic insulation question. I have read everything that I can find on the subject and there are still a couple of things that leave me scratching my head.
I am in midcoast Maine, inland, zone 6A. I will be converting 2 attics in the house into light use conditioned space, mainly for storage for the time being and maybe more down the road. Not knowing what the future holds for them I would like to get the insulation details correct.
The house was built about three years ago and everything is still in new condition. The first room that I’d like to insulate is a cape style 12/12 pitch roof over a garage. It is comprised of free span attic trusses with an engineered floor that is 2′ deep from upper to lower chord insulated with what was r49 cellulose under the floor(some settling has occurred). The rafters are 2×8.
With the attic above a garage I am concerned with air quality, moisture from snow in the winter, and fire. Sealing of the garage floor will be done in the spring to allow for removal of water and slush via a squeegee and not allow it to be absorbed into the cement only to evaporate later. The ceiling of the garage was air sealed before the cellulose was installed over the drywall but will perform a double check on that before closing the attic floor up tight.
I plan to air seal the floor after adding cellulose in the remaining floor cavity and install a hrv in that room.
Moving on to the Attic insulation, I have added 2 layers of r6 comfort board behind the kneewall and will be adding r15 roxul in the stud bay of the kneewall. See Pic below….
I feel its best to keep a vented assembly to help remove any bad air that may migrate through the ceiling of the garage. This is where I get a lot of differing opinions and seemingly contradictory information. R49 and depth are the obvious problem. The knee-jerk reaction by everyone I’ve talked to is Spray 5″ of spray foam under the roof deck and be done with it(r33.5ish). I’m just not comfortable with that. I know there is no love for closed cell foam on here. But can anyone see a problem with putting an r23 batt of roxul with a 3″ air gap to the roof sheathing in the rafter bay, and then adding 7/16 Osb under the rafters
和喷涂一层连续的4“封闭细胞to the underside of the 7/16 Osb? I would fabricate a standoff bracket out of strapping or 3/4″ osb to minimalize any thermal bridging through the spray foam and still have a nailer for the drywall. A theoretical r49.8. The 4″ of closed cell should be a sufficient vapor barrier and the roxul should be able to dry nicely if needed. In the end the real question that I have would be, is the batt in the rafter bay actually doing anything? I like the idea of it being in there because of its fire retardancy. But I have to think that more cold is coming through the rafters than heat through the closed cell. Also, If return on investment isn’t there, can it hurt having it in there? Any thoughts on the subject are greatly appreciated. I enjoying reading the responses in this Q&A section.
PS，3英寸气隙来自由固定在after上的废料制成的1英寸毛茸茸的条。
GBA Detail Library
由气候和房屋部分组织的一千个建筑细节的集合
答复
Is the roof currently set up with soffit and ridge vents to ventilate every rafter bay?
R23 rockwool in a 2x8 rafter bay will leave a 1.75" gap, which is good. If you are willing to do foam inside the rafters, go for 4-5" of reclaimed or polyiso seconds screwed and taped. Fur over the foam and drywall or 23/32 OSB screwed through the foam.
谢谢回复。是的，在拱廊和山脊通风口。当您在the子中说Polyiso时，您是在说而不是Roxul？我曾经想过这一点，但是我不确定二手polyiso的火评级，并在另一个线程中阅读，当rvalue变冷时，rvalue会很快下降。那是我最初的计划。
When I said inside, I meant inside the room. Often times people don't want to loose space inside the room and deal with the reduced R value.
连续绝缘非常有效。海湾中的R23，内部仅2.5英寸的Polyiso连续（R14-15），R37的总绩效将高于海湾中CCSPF的7英寸R49。这是一个很好的计算器：https://ekotrope.com/r-value-calculator/
I said 4-5" of polyiso, but 2-3" is probably all that is really needed on a vented assembly.
实际上，当第一次布置时，计划是3层2英寸的Polyiso直接固定在the子上。如果我回到这个想法，我仍然会有一个空的after湾。不足以抑制火，您是否认为将R23 Rockwool放入该腔实际上是该组件的任何真正的rvalue吗？
我不会进入the子，但是看着您的照片，我相信您应该在地板向膝盖的过渡时添加坚实的阻塞，并在膝盖沃尔向r子过渡时进行牢固的阻塞。
Also I believe you are missing an air barrier on the kneewall unless I dont understand your finished assembly.
看来我遗漏了它。但是OSB也在膝盖墙的前部，空气密封，然后将隔热材料应用于OSB。舒适板实际上是在地板上的上弦的热中间。我们只是没有一个好地方。所以我们走到了the徒的高峰。
我肯定会把岩刀放在the子中。以20％的框架分数为总墙壁增加了R16.8，所以绝对没有。它也很容易。3英寸的泡沫使用螺钉比6英寸更容易撞到afters。您还可以在这种方式内获得更多空间。
Mike is referencing blocking at the kneewall as a code requirement for fire blocking. The air barrier on the inside of the kneewall seems pretty straight forward.
我不知道在像您这样的地板上是否有任何细节。您要确保空气不能在地板护套下洗涤，如果有任何沉降，这是一种风险。理想的设置似乎会将空气屏障延伸到膝盖墙的车库天花板，或者沿着膝盖墙后面的车顶线。
谢谢（你的）信息！因此，巴特将进入。舒适板沿着膝盖的长度延伸到干墙。我想我认为一旦将其与地板上的纤维素结合在一起，就足够了。这就是为什么我没有将泡沫用于该应用程序。我喜欢蒸气开放地板的想法，它在车库上。希望任何不良的空气都可以被吸引出来，而不会进入房间。我会重新评估我的计划。山墙末端的地板也将被密封。非常感谢！
Vapor is related to moisture, not air movement. An air barrier may be vapor open (allow moisture to pass), but still be an air barrier. Your garage ceiling and interior air barrier should block air from the garage.
您不希望空气渗透地板护套和纤维素之间的空间。如果纤维素和地板之间存在任何缝隙，则大量的空气将直接流过您的舒适板并绕过纤维素。当风在一堵墙上吹来，从地板的一侧到另一侧的压力差异时，尤其如此。您将需要将空气屏障（胶合板，好OSB或泡沫板）延伸到下面的天花板，以包围纤维素。
Sir, thank you very much for your time and willingness to lend a hand. I will run the osb down to the drywall.
编辑：此处的任何人都可以评论使用Densglass护套作为空气屏障吗？似乎很容易使用...