Here is a great article about how to insulate a basement.

www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems

A lot of energy is lost by a unfinished basement.

Here in Quebec we had a frozen january. 1 week it was -30 F without counting the wind. With wind it was like -50 F.

Im redoing right now my basement, i put 2 inches foam (R-10) and a batt insulation (R-14) for a total of R-24.