Just how much insulation is really required in a basement?
How high an R-factor of insulation you put in your basement depends on where you live; simply check with local codes for the minimum ratings. However, if you want to create a comfortable living space that has heat and moisture control, you must insulate the whole wall right to the floor. Why? Concrete does little to stop heat flow and the soil doesn't help much until you get deep into the ground. Following the minimum ratings set by many local building codes and insulating only 60 cm (2 ft) below grade will make the basement a good storage space, but not comfortable enough to use as a living area; a bit like walking around in your Bermuda shorts in the snow. The best insulation job is done during new construction, with insulation on the outside from the foundation footings right up to the roof rafters covering the whole wall. During renovation, you can get similar results for the basement by insulating 60 cm (2 ft) into the soil and skirting 60 cm (2 ft) out, but this requires a lot of digging. If you are insulating from the inside, make sure to insulate the entire wall, and to cover the insulation in the joist area with a vapor barrier.