Double-pane windows with low-e coating on the glass reflect heat back into the room during the winter months.
Use a heavy-duty, clear plastic sheet on a frame or tape clear plastic film to the inside of your window frames to reduce drafts.
Install tight-fitting, insulating window shades on windows that feel drafty after weatherizing.
Close your curtains and shades at night to protect against cold drafts; open them during the day to let in warming sunlight.
Install exterior or interior storm windows, which can reduce heat loss through the windows by 25%-50%. They should have weatherstripping at all movable joints; be made of strong, durable materials; and have interlocking or overlapping joints.
Repair and weatherize your current storm windows, if necessary.