The Trouble With Basements
Would you ever be satisfied with single-paned windows in your house? Probably not. But did you know that typical foundation walls, even though they may be 8 inches of concrete or concrete block, have about the same insulation value as a single pane of glass? On top of that, concrete is actually surprisingly air permeable.
Nine times out of ten, uninsulated foundation walls are the single largest source of heat loss. Air sealing is a good first step, since it costs a lot less to address than insulating and is easier to mitigate, but that doesn’t solve the major heat-loss issue in basements.
There are many different ways to properly insulate a basement. For good construction details on insulating foundations properly, check out the Builder’s Guide series for various climates by Joe Lstiburek (see Access).