By insulating your home you'll make it more energy efficient in both winter and summer.
Insulation prevents outside air from getting in and inside air from getting out.
Preventing drafts at doors and windows by the use of sill casings is one of the simplest ways of saving energy dollars. Sill casings are cloth-filled tubes that are placed at the base of the doors and windows to prevent the escape of heated or air conditioned air. Until you can get the sill casings made, bath towels or throw rugs can be used to seal off air flow through doors and windows.