Can you insulate an existing slab on grade floor?
Our house was built in the seventies as slab on grade. Apparently they didn't used to put much insulation under the floor because it is freezing cold in the Vermont winters. I've never measured it but I'm pretty certain the floor is actually below freezing some days by the sliding glass doors.
We've had a few energy analyses done, and received recommendation to insulate around the outside of the foundation with 4 inches of closed cell foam sheets up to the bottom of the siding. We're hesitant to do this due to cost and aesthetics, and being uncertain if it will solve the cold floor issue.
Is it possible to insulate beneath an existing slab on grade floor? If so, how, and is it cost effective?