Improving your attic insulation, providing shade for your windows, and controlling moisture around your home are good ways to prepare your home for summer heat. Your air conditioner will cool your home better and use less electricity if you have a well insulated, well shaded, and dry home.
Solar energy transmitted through your roof and ceiling is one of the largest causes of summer overheating. If your attic has less than 6 inches of insulation, consider having another 6 to 10 inches installed. In addition, either you or your contractor should seal air leaks in the attic before insulating. Since attic insulation itself doesn’t stop air, the gaps around chimneys, plumbing vents, and light fixtures should always be sealed before installing attic insulation.
Solar energy entering windows also contributes to summer overheating. Awnings and solar screens provide excellent window shade because they stop the solar heat before it enters the home. Interior window treatments aren’t quite as effective since they dissipate some heat into the home, though opaque roller shades and reflective venetian blinds can reflect up to half of the solar heat back through the window.
Dampness around your home reduces summer comfort and increases air-conditioning costs. Air conditioning is a very expensive way to dry out a damp home. Instead, install plastic sheeting as a ground-moisture barrier on the floor of your crawl space, install gutters and downspouts where needed, and consider installing a sump pump if you have an extremely wet basement or crawl space. You can also help dry your home by cutting shrubs and plants away from your foundation to encourage air circulation.
Both Your Home Cooling Energy Guide and The Homeowners Handbook to Energy Efficiency have extensive information about maintaining comfort and reducing air-conditioning costs.