# Insulating interior basement walls



## brazzle (May 2, 2011)

Hello,

First, I'd like to apologize for my lack of experience---I'll likely use some incorrect terms.

I just bought my first house and the basement has a partially-finished room that I would like to use for an office. It is wired, vented, and has drywall up with 2 walls being external and 2 being internal. Unfortunately, they failed to insulate the external walls before, so I know I need to do that. My home inspector suggested having loose insulation sprayed rather than taking down the walls.

My question is regarding the two interior walls. Do I need to insulate these from the rest of the unfinished basement? Eventually I would like to finish the entire basement, but it would likely be a year or two before that happens. 

Thanks


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## Gary in WA (Mar 11, 2009)

Welcome to the forum!

Where are you located?

Is there poly sheeting plastic on the concrete?

Gary


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## brazzle (May 2, 2011)

Thanks for the reply. I am located in Utah and no, there is nothing covering the concrete walls and the ceiling has exposed batting in the non-finished areas.


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## Gary in WA (Mar 11, 2009)

You are in either Zone 5 or 6; http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_11_sec001_par001.htm

http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_11_sec002.htm

I recommend using rigid foam board glued tight to the concrete wall with no vapor barrier: http://www.buildingscience.com/documents/information-sheets/5-thermal-control/basement-insulation

In the unfinished area, I would install a house wrap as an air barrier on the floor joists to prevent wind-washing of the fiberglass; http://www.diychatroom.com/f98/biggest-loser-fiberglass-insulation-90438/

Foam board the rim joists after air sealing any/all wiring/plumbing holes to above; http://www.buildingscience.com/docu...arriers/critical-seal-spray-foam-at-rim-joist

http://www.wag-aic.org/1999/WAG_99_baker.pdf

Gary


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