Q: mentioned insulating the ceiling of your basement, what about insulating just the sill?

A: The sill (the area above the concrete foundation and the floor joists) is a major source of drafts and heat loss in a house so sealing gaps and insulating it makes a lot of sense. However, don’t stop there. The ceiling of the basement losses a lot of heat from the house to the outside and insulating that will greatly reduce your heating bills and carbon emissions.