According to the Department of Energy, heating and cooling account for 50 percent to 70 percent of your energy costs. If your energy bills are out of hand, the culprit may not just be your fuel or electric provider. It could be the cracks and crevices in your home that let valuable heat and cold air out of your house. If you insulate your house properly, you will save money while enjoying a warmer home in the winter and a cooler house in the summer.

Windows

Use weatherstripping to insulate your windows. The weather strips have adhesive on the back, so simply clean the surfaces, remove the backing and place the stripping along any gaps in the sashes. In the winter, you can also use plastic-sheet kits. Place double-sided tape along the frames of windows, and press the the plastic sheets in place. Use a blow dryer to seal the plastic and shrink it firmly to the window.

Doors

The bottom of your front and back doors can sometimes have a small gap that allows cold and warm air in. Nail a door sweep, a simple metal or rubber strip, to the bottom of your door. You can also purchase a door draft guard for this purpose---simply slide it along the base of the door and close the door. Open the door and place adhesive weatherstripping on the sides and top of the inside frame.

Attic and Basement

Seal the leaks in your attic, basement and crawl spaces with a caulking gun or foam (this comes in a spray can). Wait for a cool day to go into these rooms so that you can feel where the air is leaking in with your bare hand and plug up the holes.

Walls

If you are interested in doing a more thorough insulation job, you have to work on the walls of your home. It is very expensive and time-consuming to redo the insulation of an old house---the walls have to be gutted, insulated with fiberglass, and then closed with drywall and plaster again. Call a professional carpenter or contractor to take care of this work. If cost is a concern, there is also a less expensive alternative that may work for your home. There is a foam called Icynene that can be injected directly into your walls to help insulate them. Once injected, the substance expands and sets into place.

Source:

Department of Energy; Why Insulate Your House?

Graber; How to Insulate an Old House