According to the US Department of Energy, up to 45% of a home's energy loss is through the attic, but the amount of heat actually lost will depend on where you live and how cold your attic gets. Therefore, homes in colder climates require higher insulation values. Recommended attic insulation levels range from R19 in the southern most parts of the US to R49 in the northernmost. Consult your local building authority for recommended levels in your area.
Click on the insulation you currently have and then the insulation you would like to add
to see how much heat you could save.