EPS exterior insulation thickness
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Looking to purchase a 1975 home with 2×4 cavity filled walls. This house will be stripped back to the studs on the interior and the exterior windows and doors replaced as well as siding. I want to add a few inches of eps insulation to the exterior with strapping. How much insulation is required so the walls can still dry to the exterior as I will have interior poly? I live in edmonton alberta Canada. Your guys help is much appreciated
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Sheldon,
To answer you question, you need to know your climate zone.
Looking at this map of Canadian climate zones, it looks like Edmonton, Alberta is in Climate Zone 7.
Once you know you climate zone, you can consult the table showing minimum thicknesses for exterior wall foam in this article: Calculating the Minimum Thickness of Rigid Foam Sheathing.
In your climate zone, the minimum R-value for rigid foam installed on the exterior side of a 2x4 wall is R-10. If you plan to install EPS, that means that the EPS has to be at least 2 1/2 inches thick.