# insulation touching concrete in basement



## ron0805 (Oct 1, 2009)

Im framing my walls in my basement, the exterior first.Im useing metal framing and i want to 2 1/2 studs to give me more sq footage.My question is if i do that and leave myself some space behind for clearance,then use 3 1/2 batt insulation it will touch the concrete,im thinking that will be a problem in the long run.

THX


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## Scuba_Dave (Jan 16, 2009)

You do not want the fiberglass insulation touching the basement walls
Ideally you want 1" of air space behind the insulation
Or use rigid foam boards up against the basement walls...then studs


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## bjbatlanta (Jul 16, 2008)

And by compressing the 3-1/2" insulation into the 2-1/2" cavity you would actually lose R-value....


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## seawiz (Feb 22, 2010)

Just curious, why is it a problem if the insulation touches the basement floor?


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## soasquad (Jan 9, 2010)

You might want to read this before you get started. I would NOT use fiberglass! You will just end up with mold!

http://www.homeconstructionimprovement.com/how-to-insulate-basement-walls/#comment-36170

http://www.eere.energy.gov/buildings/building_america/pdfs/db/35017.pdf


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## Gary in WA (Mar 11, 2009)

"use 3 1/2 batt insulation it will touch the concrete,im thinking that will be a problem in the long run." ----- correct: http://www.swinter.com/services/documents/ChallengesofBasementInsulation.pdf

http://www.buildingscience.com/docu...rol-for-new-residential-buildings?full_view=1

No air space behind the insulation: http://oikos.com/library/insulating_framed_walls/index.html Glass batt relies on the small air spaces to work properly. A bigger space allows air currents to form defeating the whole idea of still air. AND, fire-stopping is required every 10' horizontally and vertically, per safety code.

Be safe, Gary


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