Air sealing is a must. This involves eliminating drafts around holes, seams, and gaps in floors, walls, and electrical and duct work.
Some renovated homes may claim to be air tight, but this tends to degrade indoor quality. All Energy Star-certified homes are required to have proper ventilation to allow a certain amount of fresh air to enter with the windows and doors closed.
Other benefits, besides reduced heating and cooling costs, include less outside moisture and quieter rooms.
Susan Farley for The Boston Globe