Cost vs Benefit: Under-slab insulation, Zone 4?
Looking into 2″ XPS or similar underneath the slab before pouring.
For Zone 4, approx 17 degrees F outdoor heating temp (99%) and 91 degrees F outdoor cooling temp (1%), what are the benefits of slab insulation?
For winters, if the foundation is 8-9 feet deep, which is below the frost line, is there sufficient cold through the slab to make the insulation worthwhile?
For summers, isn’t there a cooling benefit from ground temps, that might be lost with the insulation?
other benefits (moisture?) from slab insulation?
The basement will be a walkout, so I can sort of see the benefit at the walkout end where the slab is at ground level. Builder said it’s standard to insulate adjacent to walkout, but not sure about rest of the floor.
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