Replies

1. 
   charlie_sullivan|Oct 18, 2015 09:35pm|#1

   How deep is the cavity, and what climate zone are you in (or zip code)?

   您是否愿意考虑除闭孔喷雾泡沫以外的其他选择？（我认为这就是您的意思，尽管还有其他类型的闭孔泡沫）

   How and where are the attic and kneewall spaces insulated, or is that work you want to plan in conjunction with this?

2. 
   berryjb|2015年10月19日上午08:17|#2

   Charlie, the cavity is only 4 1/2 to 5 inches deep, and has a lot of nails coming into it from the roof - I'd thought about trying to slide in board board (then spray foam the boards in), but the nails, and other miscellaneous debris get in the way. We're in climate zone 5 - so even if I can truly fill the cavity with closed cell foam I won't reach recommended min R38 - but I'd at least get good sealing and much better than nothing R value. I'm figuring I need to turn the whole assembly into unvented space. I can access both attic space and knee wall to overcome the current poor use of fiberglass. Thanks! Jim

3. 
   berryjb|Oct 19, 2015 08:18am|#3

   Ooops - meant to say slide in foam board ...

4. GBA Editor
   马丁·霍拉迪（Martin Holladay）|2015年10月20日09:04 AM|#4

   吉姆，
   You wrote that your ceiling has "plaster lathe and drywall on top." I'm guessing that the plaster is actually on top -- it's older -- and that the drywall was installed later, on the interior side of the plaster (putting the plaster on top and the drywall on the bottom).

   如果我的猜测是正确的，我建议您在干墙天花板上钻孔很容易，因为您需要的孔尽可能多，因为干墙很容易修补。

   就是说，我认为您不想钻孔以安装喷雾泡沫。喷雾泡沫安装程序需要出色的访问才能做得很好。他们需要开放的，裸露的框架托架 - 而不是一系列漏洞。

   您可以询问任何当地承包商是否安装了低曝光浇注泡沫。这种方法的评论好坏参半 - 可浇注的泡沫会松散天花板。

   最好的方法是将刚性泡沫安装在现有屋顶护套的顶部，然后再安装另一层屋顶护套和新的屋顶。当需要新屋顶时，请记住这种方法。

5. 
   berryjb|2015年10月20日10:05am|#5

   Martin - sorry for my poor description - you're exactly correct. Is the primary concern about the pourable foam that it would pop the ceiling, or are there additional issues? Is pourable also closed cell?? I'd gotten some guidance from a foam contractor that one should not apply closed cell more than a couple of inches per applications, to ensure it does not combust during curing. Thank you - Jim

6. GBA Editor
   马丁·霍拉迪（Martin Holladay）|2015年10月20日上午10:17|#6

   吉姆，
   I don't have much experience with pourable foam. I know that most contractors stay away from it, so any speculation is worthless unless (a) you can find a contractor who will install this product, or (b) you want to do the work yourself.

   Pourable foams are used by boat-builders as well as insulation contractors. There are definitely closed-cell foams in this category. Here are some links -- not necessarily the most relevant links:

   http://www.uscomposites.com/foam.html

   http://bertram31.com/proj/tips/foam.htm

   http://www.aeromarineproducts.com/boat-foam.htm

7. 
   berryjb|Oct 20, 2015 11:31am|#7

   马丁，谢谢您的链接 - 我可能不得不为此付出代价。当它确实到了，我希望在甲板上涂上一层泡沫板，但是我将无法添加超过1英寸的泡沫板，而不会影响窗户窗户的底部，并且（希望）我不必多年了，所以我想从腔体开始。中间的三分之一），这样他们会阻止空气排气吗？

8. GBA Editor
   马丁·霍拉迪（Martin Holladay）|Oct 20, 2015 11:46am|#8

   吉姆，
   Whenever you insulate a sloped roof assembly, you have to follow certain rules -- both building science rules (designed to keep your roof sheathing from rotting) and building code rules. Here is a link to an article that explains the rules:How to Build an Insulated Cathedral Ceiling.

   If an insulated sloped roof assembly is designed to be vented -- the usual method when air-permeable insulation like fiberglass or cellulose is used -- then these vent channels shouldn't be blocked. They need to be uninterrupted, from soffit to ridge.

   If you want to install closed-cell spray foam in the middle third of your roof assembly, you would ordinarily also need to install the same type of insulation in the bottom third of your roof assembly. If the top third of the roof is an attic, that attic can be insulated differently.

   一英寸的刚性泡沫具有R-4的R值为R-6。如果您可以在屋顶护套上方安装全部，我希望您生活在1、2或3的气候区域。如果您住在任何地方，该方法将无法正常工作，因为我链接的文章中解释了这种原因。