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Rigid foam on basement walls

digger100's picture

Hi,
I'm in the process of building a workshop in my basement.  I'm using 2" Rigid foam boards, glued and taped to the exterior walls.
 
I was going to use spray foam to seal the top and bottom of the boards. The plan is to than put up 2x4 walls in front of the foam,
 
and than drywall. I've read conflicting articles on using unfaced insulation in the 2x4 walls. Some say to use it, some say its
 
optional.
 
So, a few questions.
 
Is it necessary to fill the 2x4 wall with fiberglass insulation ?  Would an option be to use 2x3's flat on the 2" foam, and not use
 
batts ?   I need to leave room for electrical boxes, etc for the workshop.
 
 
Also, I was also going to fit foam along rim joists and wanted to know if those areas should also be covered with drywall, for fire
 
blocking purposes. The ceiling will probably remain open.
 
 
House was built in 1955, live in Rhode Island, which I believe is zone 5.
 
Thanks

Additionaly insulation (post #206902, reply #1 of 1)

Additionaly insulation certainly is not "necessary" -- 2" of foam is a fair amount of insulation for a basement -- but it won't hurt.  You can do additional insulation several ways -- more foam, fiberglass compressed into a thinner space, etc.  Any additional insulation can be cut out to accommodate electrical boxes and the like -- there won't be a serious loss of effectiveness.

Generally speaking, foam insulation should be covered with drywall, for fire safety reasons.  How important this is depends on the type of foam.


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