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Community and Q&A

How much exterior insulation on Basement wall to prevent condensation?

JayMart | Posted in General Questions on

Climate Zone 5 – I have 2″ of EPS on the exterior of my foundation walls. Although the brick shelf  (above grade) I have is not insulated. Is 2″ enough to keep my walls warm enough to prevent condensation from forming?

From what I understand we want more than 50% of the entire r-value of the wall assembly to be on the outside to prevent condensation. In this case, I have R10 of the total required R19. 

I ask because I need to decide if I’m going to apply a vapor barrier to the inside part of the wall assembly (with either Closed Cell spray foam or a liquid applied vapor barrier and w/1″ of Dow Thermax.)

Any advice on what I should do in this situation? 


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  1. Expert Member


    This article has the amount necessary by climate zone.

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