Use energy wisely, don't forget the outside of your home
If a playing card fits the crevice of an outside door or window, you need more weather stripping. Caulk and weather-strip to stop air leaks around windows, doors, exhaust fans and any other place where wires or pipes pass through walls. Replace any caulk that has cracks or is no longer soft.
You can install storm and/or replacement windows, but they may not be the best use of your energy improvement dollars because of their high cost and long payback. A low-cost alternative is 6-mil plastic, which you can use to "make" storm windows. Be sure to stretch it as tightly as you can. If you use these homemade storm windows on the inside of your regular windows and attach them carefully, they can last through several seasons. You can also find homemade kits at home improvement stores.
Keep out winter air by covering your window air conditioners tightly on the inside with thick plastic or special air conditioner covers. Weather-strip around the units to block drafts.
Cover bare ground beneath your home with a vapor barrier to keep moisture from getting into your home. Polyethylene sheets work well. Since a third of your air conditioner's energy is spent removing moisture, vapor barriers can make a noticeable dent in your energy bills.
If you have a crawlspace, open your foundation vents each spring and close them each fall.
Planning to replace your roof? Consider roofing materials with reflective coatings and/or choose light-colored roofing to greatly reduce heat absorption.
Carefully plan your landscaping to help to reduce your energy costs and increase indoor comfort.
Plant deciduous trees like oak, maple, gum, ash and dogwood. They lose their leaves in the winter, letting the sun through to warm your home. In summer, their leaves shade your home. Plant shade trees to the south, since that side gets the most sun.
Evergreens are effective for blocking wind. Plant them in a staggered or double line to the northwest of your home.
Smaller foundation plants can minimize the loss of cool air away from the house in summer and, in winter, provide additional wind protection.