Actually, the majority of energy loss is through a building’s roof—not windows—so attic insulation with an R-value of 38 or more is great for both old and new homes. Properly maintained old wood windows are generally better fitting with fewer areas for drafts, so while single-pane glass may be colder than double-paned, there is less heat loss in areas around the window. Paired with storm windows, historic wood windows can be more energy efficient than new windows. In most cases, the time it takes to realize the savings from replacement windows is often past the expected life of the window. For more information on preserving historic windows, read “Preservation Brief #9: Repair of Historic Wooden Windows.”