Single-pane glass with no storm windows
Single-pane glass with storm windows
Double-pane (insulated glass)
Double-pane low-E or gas-filled
Bare concrete or brick, inside and out
Finished and insulated on the inside with fiberglass
Insulated with foam on the exterior
Made with insulating blocks (insul out and in)
More than 20 years old
Don't know but they look old
Less than 10 years old, low-flow
Relatively new, low-flow all the way
An oil burner more than 20 years old
An old oil burner, but insulated ducts
A gas burner less than 10 years old
A high SEER gas furnace
Geothermal Heat Pump A geothermal heat pump
Heat pump or Mini-Split System
Under 500 sq. ft.
1,000 to 1,500 sq. ft.
2,000-2,500 sq. ft.
3,000-4,500 sq. ft.
More than 5,000 sq. ft.