Insulating around concrete wall before cementing floor

[Bottlecapdigger]

My question is, is there any reason to insulate on the inside of the concrete wall any more than the thickness of the floor? The floor will also be insulated and with infloor heating. Insulate with 2" blue foam panels that is. The panels come in 2x8 ' and I was going to rip then in half so the top of of the panel is just under the floor surface and go down 12 " . With a 5" thick floor , 7 " would then be below the floor . Would this be ok? .is this insulated low enough? Or would l still lose heat through the wall? We're in Ontario. Thanks. BCD

 

[Radix2]

you definitely want to insulate down to the frost line - it is even more important than insulating under the floor.

The ground is far more conductive of heat than the air, so allowing the cold to go under the building is bad. allowing the cold to go under the building could allow frost to heave the floor. allowing the cold to go under the floor make that insulation lose more heat.

The good insulation design guidlines out there show more insulation in the foundation walls than under the floor (say r-15 in the walls, R-10 under the floor.

I built my foundation walls out of ICFs so I have R-20 there, then did 4 inches of foam under the floor for the first 4 feet ( R-16), then did the 2 inch foam in the middle of the floor for R-8. we insulated the inside of the footings too.