Cut back the transfer of heat through the roof and walls. If the attic isn’t already insulated or is underinsulated, insulate your attic NOW. This will give you the greatest change in comfort for the least amount of expense. Before you buy, see the Home Insulation Buying Guide. Weatherize your home to reduce the loss of conditioned air. Employ caulk and weatherstripping to cut back on the transfer of air.

Install a foil radiant barrier in the attic. Staple it to the underside of the roof rafters, allowing an air space between the foil and the roof sheathing. Place staples about 3 inches apart. Position seams between sheets of foil centered on the rafters and seal the seams with caulk.

Install inexpensive heat-reflecting film on windows that face the sun. This will keep your house cooler and reduce glare and ultraviolet rays that damage furniture and floors. For hot climates, sun-control types are most effective, but be aware that they will reduce the amount of light that comes in through the windows. In climates where cold seasons are also a problem, choose a combination film (but do not apply it to south-facing windows if you want to benefit from the sun’s warmth during winter).

Reduce heat gain by pulling drapes or shades, and use shelters to prevent direct sunlight from streaming in through windows on the south- and west-facing sides of the house. Overhangs, patio overheads, latticework, awnings—all of these work well.

Plant now to provide shade in the future. Trees, large bushes, and vines can provide shade and cooling evaporation. Choose deciduous varieties if you want to allow the sunlight to warm the house during winter. Pay attention to the growth characteristics of any landscaping that you plant to be sure it will be appropriate for the need and will not block breezes.

Closely monitor the temperature both inside and out with an indoor/outdoor thermometer. When it is cooler outside, open up windows and doors to ventilate. (Be sure your windows and doors have adequate screens to prevent an influx of bugs.) And arrange furniture and drapes so they don’t restrict airflow. If you have operable skylights or transom windows high on walls, open them to let out super-heated air and create convection currents.

Use portable fans or ceiling fans and the “Fan Only” setting on your heating system’s thermostat to keep the air moving. By doing so, you will feel comfortable in a room that is 2 or 3 degrees warmer than a still room. If your home has a whole-house fan, turn it on to extract warm air.

Humidity makes room air feel warmer, so reduce indoor humidity. Minimize mid-day washing and drying of clothes, showering, and cooking. When you must do these things, turn on ventilating fans to help extract warm, moist air, but be sure to turn them off when you’re finished so they don’t extract cooled air from the house. Also see our section on dehumidifiers.

Unless you absolutely need them, turn off incandescent lights and heat-generating appliances. When it’s time to cook, opt for the barbecue instead of the range.

If you try all of these measures but are still suffering from the heat, maybe it’s time to consider installing an air conditioner. See the section on room air conditioners for information on how to select an efficient, high-quality model.