Do I need to insulate the interior foundation wall if I already have 2 inches of rigid XPS on the exterior?
My builder put up a 2×4 wall in my mechanical room against a concrete wall for my HVAC guy to mount the in-floor heating system. He wants me to put up 1/2″ plywood over the stud wall for the install. Like I said, I have 2″ rigid foam around the exterior of the foundation (This is a walkout basement, so foam is around 3 sides of the foundation), but this concrete wall is actually separating the mechanical room and 6′ of sand fill below the garage and below grade. There is no foam on this wall (it’s almost like an interior concrete wall???) If it matters, the garage concrete floor also has in-floor heat.
Is the any reason to insulate this wall? If so, what is the best method now that the stud wall is already there.
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