First, test your home for air tightness. On a windy day, hold a lit incense stick next to your windows, doors, electrical boxes, plumbing fixtures, electrical outlets, ceiling fixtures, attic hatches, and other locations where there is a possible air path to the outside. If the smoke stream travels horizontally, you have located an air leak that may need caulking, sealing, or weatherstripping.
Caulk and weatherstrip doors and windows that leak air.
Caulk and seal air leaks where plumbing, ducting, or electrical wiring penetrates through exterior walls, floors, ceilings, and soffits over cabinets.
Install rubber gaskets behind outlet and switch plates on exterior walls.
Look for dirty spots in your insulation, which often indicate holes where air leaks into and out of your house. You can seal the holes by stapling sheets of plastic over the holes and caulking the edges of the plastic.
Keep all south-facing glass clean.
Make sure that objects do not block the sunlight shining on concrete slab floors or heat-absorbing walls.
Consider using insulating curtains to reduce excessive heat loss from large windows at night.
Install white window shades, drapes, or blinds to reflect heat away from the house.
Install awnings on south- and west-facing windows.
Install storm windows over single-pane windows or replace them with double-pane windows. Storm windows as much as double the R-value of single-pane windows and they can help reduce drafts, water condensation, and frost formation. Storm windows can reduce your heat loss through the windows by 25% to 50%. Storm windows should have weatherstripping at all moveable joints; be made of strong, durable materials; and have interlocking or overlapping joints. Low-e storm windows save even more energy. As a less costly and less permanent alternative, you can use a heavy-duty, clear plastic sheet on a frame or tape clear plastic film to the inside of your window frames during the cold winter months. Remember, the plastic must be sealed tightly to the frame to help reduce infiltration.
For new construction, reduce exterior wall leaks by either installing house wrap, taping the joints of exterior sheathing.