Replies

1. Expert Member
   Zephyr7|Sep 17, 2021 08:11am|#1

   Closed cell spray foam is safest, but you still need to have the right ratio of spray foam to batts (“fluffy stuff”) for your climate zone.

   I’m not sure why you would prefer flash and batt here. I would probably just do a fill of spray foam to the required R value. You can do that either with closed cell foam alone, or you can put in enough closed cell foam for moisture control under the sheathing, then fill the remainder of the spaces between the rafters with open cell foam (which is a little cheaper).

   Bill

1. 
   Patrick OSullivan|Sep 17, 2021 08:59am|#2

   Unless I'm misunderstanding the assembly, it sounds like the roof is vented above, so all fluffy or open cell in the bays could be an option.

1. 
   Dwight Foreman|Sep 17, 2021 09:02am|#4

   Hi Patrick, you are correct. The reason I made this post was to get some clarity on the space between the metal roofing and the sheathing and what options that would allow.

2. 
   Dwight Foreman|Sep 17, 2021 08:59am|#3

   Hi Bill, thanks for the comment. Foam in Louisiana is extremely costly for some reason. I also like the benefits of rock wool. I am mindful too of the climate cost of foam.