Home Maintenance Tip: Preventive maintenance of the heating and air-conditioning units is all about ensuring proper air flow. Vacuum vents before using the units for the first time each year, and then inspect the vents periodically to make sure new dust hasn't accumulated. Change filters as soon as they become soiled. Finally, keep furniture and window coverings away. In the case of heat vents, this is as much a safety issue as a maintenance one. Don't turn off your heat or A/C when you leave for the day. Instead, turn the heat down or the A/C up just a few degrees. You'll actually save more energy by maintaining a steadier temperature.