What’s more, heating and cooling systems in the United States together emit over a half billion tons of carbon dioxide into the atmosphere each year, adding to global warming. They also generate about 24% of the nation’s sulfur dioxide and 12% of the nitrogen oxides, the chief ingredients in acid rain.

No matter what kind of hvac systems homeowners have, they can save money and increase comfort by properly maintaining and upgrading their equipment. But it should be emphasized that installing an energy-efficient furnace alone, for instance, will not have as great an impact on energy bills as taking a whole-house approach.

By combining proper equipment maintenance and upgrades with appropriate insulation, weatherization, and thermostat settings, homeowners can cut their energy bills, and their pollution output, in half.

The following are some energy-saving heating and cooling tips from the DOE:

• Set the thermostat as low as is comfortable in the winter and as high as is comfortable in the summer.
• Clean or replace filters on furnaces once a month or as needed.
• Clean warm-air registers, baseboard heaters, and radiators as needed. Make sure they’re not blocked by furniture, carpeting, or drapes.
• Bleed trapped air from hot-water radiators once or twice a season.

  If the homeowner is in doubt about how to do this, s/he needs to give you a call.

• Place heat-resistant radiator reflectors between exterior walls and the radiators.
• Use kitchen, bath, and other ventilating fans wisely. In just one hour, these fans can pull out a houseful of warmed or cooled air. Turn fans off as soon as they have done the job.
• During the heating season, keep the draperies and shades on south-facing windows open during the day to allow sunlight to enter the home and closed at night to reduce the chill from cold windows.

  During the cooling season, keep the window coverings closed during the day to prevent solar gain.

• Close an unoccupied room that is isolated from the rest of the house, such as in a corner, and turn down the thermostat or turn off the heating for that room or zone. However, do not turn the heating off if it adversely affects the rest of the system.

  For example, if the house is heated with a heat pump, do not close the vents — closing the vents could harm the heat pump.

• Select energy-efficient equipment when buying new heating and cooling equipment.

  You need to help the homeowner compare energy usage. Tell them to look for a high Annual Fuel Utilization Efficiency (AFUE) rating and Seasonal Energy Efficiency Ratio (SEER). The national minimums are 78% AFUE and 10 SEER.