# I have a "Poor Man's Spray Foam" question



## AGWhitehouse (Jul 1, 2011)

This is a tough installation to complete effectively and you still have a 1/2" void that allow for convective air currents. You'll also have alot of waste with the custom cuts, which is very costly garbage.

Below is a comparison of two systems...Noting the different R-values, I think you'd be better off in installation time, $, and stress level to fill the bays with unfaced batts. and sheath the wall with 1/2" foil-faced polyiso before you sheetrock. The foil-face with taped seams and penetrations will give you the air and vapor barrier needed while greatly reducing the thermal bridging that the studs create.

A whole different approach is to sheath the exterior of your house with nail-base foam panels. This would require re-siding, so I'm not sure if this is even in your deck of cards.

*OOPS...done quick and without great review, the titles of the charts are backwards. The cut foam scenario is on the right...*


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## bowlofkibble (Sep 13, 2014)

AGWhitehouse said:


> Below is a comparison of two systems...Noting the different R-values, I think you'd be better off in installation time, $, and stress level to fill the bays with unfaced batts. and sheath the wall with 1/2" foil-faced polyiso before you sheetrock. The foil-face with taped seams and penetrations will give you the air and vapor barrier needed while greatly reducing the thermal bridging that the studs create.


 Is this technique agreeable? I know this is an old post but I've been considering this idea, the one in the original post and plenty of others for insulating.


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## GeselleBrian (Apr 1, 2015)

can you not just stuff the wall with Fiberglass or Rockwool?


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## bowlofkibble (Sep 13, 2014)

GeselleBrian said:


> can you not just stuff the wall with Fiberglass or Rockwool?


 Of course that is an option, but air sealing seems to be kind of a big deal it seems and using these techniques makes the idea of air sealing much easier to fulfill. There is a video titled "Attic Insulation Done Wrong… and How to Do It Right!" (unable to post links) that might help illustrate this idea a bit.


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## Hick (Nov 21, 2014)

Air seal with expando foam, THEN put batts of insulation in The way whitehouse suggested with unfaced & foil ontop might give you better insulation.

However, faced batts of insulation will give you plenty of insulation for likely a much cheaper price. If we are going the "poor mans" route, that would likely be the cheapest & work just fine.

I understand fully about insulation. Hell my walls have outer sheath, 3/4" foil board, tar paper, inner sheath, R-13 insulation, sheetrock & cedar slats.. Dunno the exact R value but I am sure it is high. Overkill but...I stay cool in summer & warm in winter. I tried the poor mans insulation route for under my floor but was more trouble than it was worth.


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