I live in an attached house (on both sides). Do I need to insulate my basement?
I am finishing my basement. Will I have to insulate all my walls?
Yes -- I would insulate all exterior walls. Do not forget about the rim joist above the ceiling of the basement.
If you have conditioned space above your basement, no need to insulate the floor space above.
For more information:
Check our remodeling a basement Q&A to see what other homeowners and contractors are saying about basement insulation, basement flooring, etc.