Is foam under the basement always recommended?
I have been thinking about the benefit of putting XPS/EPS foam under the basement slab, and it has gotten me thinking.
I am building in zone 6, where it is quite hot for a couple of months in the summer, getting up into the 90s, and cold in the winter, getting down to the 10’s (Fahrenheit) on and off for a couple of months.
What I am thinking is – during the hot summer months, wouldn’t I want as little foam as possible between my basement floor and the cool earth that far down? During the winter, I can see how insulating the slab makes sense, since the ground will probably be 50 degrees or so, and the inside temperature will be around 70, but how does one balance the cooling benefit in summer against the energy savings in the winter?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part