Insulation with spray foam

Old 11-30-16, 11:46 AM
Thread Starter
Join Date: Dec 2012
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
Insulation with spray foam

Will the walls rot when using sprayfoam ? I live in Ohio and its pretty cold during winter and when its cold outside and hot inside I'm thinking there will be humidity in the walls and maybe its better using the glassfiber insulation instead ?

I'm living in an old two story house, ballon frame with partly knob and tube wiring. Need to look more into how much is left of that stuff. Think its partly replaced. Not sure.

If I am insulating with spray foam, can the walls be covered from the attic and down without tearing of the plaster walls ?

Thanks, I appreciate all your help!
Old 11-30-16, 01:02 PM
Join Date: May 2015
Location: USA
Posts: 3,103
Received 144 Upvotes on 117 Posts
Properly applied, spray foam insulation will not foster mold or rot. Foam is much better at air sealing than fiberglass, which is an advantage for homes without good air sealing.

You cannot install spray foam over knob and tube. I don't believe any insulation should be placed over knob and tube.

I am not aware of foam contractors that will fill a closed wall cavity; it would need to be open to use foam. Blow-in fiberglass or cellulose can be used on closed wall cavities by drilling holes at top and bottom of each cavity.
Old 11-30-16, 01:31 PM
Group Moderator
Join Date: Oct 2004
Location: WI/MN
Posts: 19,073
Received 1,248 Upvotes on 1,192 Posts
I don't believe any insulation should be placed over knob and tube.
This is my understanding as well.

Foam is a vapor retarder and can create a thermal break which keeps condensation from occurring, which makes it just about the opposite of what I think you interpreted it to be.
Old 11-30-16, 06:04 PM
Join Date: Jan 2011
Location: USA
Posts: 4,463
Received 128 Upvotes on 113 Posts
First thing you need to do is get rid of all that old Knob and tube wiring replaced and bring all the wiring from the pole to the new panel up to modern codes.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: