Replies

1. GBA Editor
   Brian Pontolilo | Jul 27, 2020 09:02am | #1

   Hi Shawn.

   There are two-part DIY spray foam kits, but I have never seen a DIY injection or "pour-and-fill," products meant to retrofit in already closed stud cavities. Are you looking to increase R-value?

1. 
   ThirtyWest | Jul 27, 2020 09:26am | #2

   Thanks for the reply Brian! I have used the 2 part spray foam kits in the past. After reading the article about closed cell spray foam not meeting its full potential, partially in part to the small space between the drywall and the foam, I had thought it may be beneficial to fill that void with some type of injection foam. Also, I was hoping to take fill any shallow spots in the foam or any areas that may have pulled off of the studs. Am I just being OCD?

1. 
   ohioandy | Jul 27, 2020 10:49am | #4

   Shawn, maybe OCD, but his kind of work does benefit from VERY careful attention to detail. If the gap is as small as you say, you're going to spend a lot of time, make a big mess, and release a bunch of greenhouse gasses for very limited gain. These between-the-stud foam fills are already compromised by all the studs acting as heat bridges, which won't change with your proposed modification. I'd take the OCD and apply it to airsealing the rest of the house, if that's not already done. Look for other places of insufficient insulation and work on those. Filling a 1/2" gap behind the drywall should come way down the list.

2. 
   nhbean | Jul 27, 2020 10:23am | #3

   Shawn,

   Tiger Foam (https://tigerfoam.com/sprayfoaminsulation/order-products/spray-foam-kits/) sells a slow-rise formula intended for filling cavities. It is sold as a two-part DIY spray foam kit, and you can add a hose to the nozzle to snake deeper into existing cavities. You can watch an instructional video here: https://www.youtube.com/watch?v=80RUaTtkXGA#:~:text=Tiger%20Foam%20Slow%20rise%20formula,attached%20using%20standard%20building%20practices.&text=Works%20well%20behind%20plaster%20and%20lathe%20walls%20or%20any%20cavity%20fill%20application.

1. 
   ThirtyWest | Jul 27, 2020 12:52pm | #8

   Hadn't seen that. thanks!

3. 
   user-2310254 | Jul 27, 2020 11:14am | #5

   Shawn,

   Maybe Dana will comment on the ROI for this type of project. But I suspect you will have a hard time recouping your cost. I'd also be concerned about blowing out walls or creating an odor problem where none existed before.

   What about increasing attic insulation or air sealing existing leaks?

1. Expert Member
   BILL WICHERS | Jul 27, 2020 12:22pm | #6

   Conventionally installed spray foam has usually little if any advantage over other insulation in terms of insulating performance when used in walls. It’s only real advantage in this application is air sealing, and there are other ways to do that. Spray foam from the DIY kits is much more expensive than the commercially installed stuff when worked out on larger jobs based on materials cost, so the kits are even less cost effective in walls than “regular” commercially installed spray foam.

   Dense pack cellulose is better in terms of air sealing than batt insulation, but you should still try to air seal with the usual methods (caulk, canned foam) for heat performance.

   I wouldn’t waste any money trying to inject spray foam into wall cavities unless you have some specific reason why it’s the only possible option.

   Bill

4. 
   ThirtyWest | Jul 27, 2020 12:50pm | #7

   Thanks for the replies! Our house already heats Ok, I guess. I was just thinking about any easy way to add some extra tightness to our basement. appreciate the input folks.