Air Vents

By Vicky Katz Whitaker

June 25, 2010 5 min read

Keeping those air vents clean is a must if you want to stay cool during those early summerlike autumn days and warm this winter. It's not just a matter of efficiency. Your health depends on it, experts say.

Today's homes are built tighter than their air-leaking older counterparts. And though that has upped the comfort level and has helped homeowners slice heating and cooling bills, it has introduced a new problem: indoor air quality.

If you don't maintain your home's heating and cooling ventilation system, allergy- and asthma-triggering dust mites, pet dander and plant and mold spores can become trapped in your home. The U.S. Environmental Protection Agency recommends changing your furnace or air conditioning filter at least every three months.

"Check your filter every month, especially during heavy use months (winter and summer). If the filter looks dirty after a month, change it," says the EPA in its online air filter advice for homeowners ( A dirty filter, it notes, "will slow down air flow and make the system work a little harder to keep you warm or cool -- wasting energy. A clean filter will also prevent dust and dirt from building up in the system."

Several types of filters are on the market. The most common is a widely available throwaway fiberglass or polyester product introduced in the 1950s that is designed to remove larger particles from the air. These traditional filters should be changed monthly. Newer disposable pleated filters have more filter surface and a higher capacity to catch microscopic dust particles, pollen, mold spores and other allergens, as well as bacteria- and virus-carrying particles. Pleated filters can be changed anywhere from every two months to once a year. Pleated, permanently charged electrostatic filters should be changed every two to three months, filter manufacturers say. Filters should fit snugly. If a filter is loose around the edges, air will flow around it instead of through it.

All filters carry a MERV, or minimum efficiency reporting value. This rating scale was developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers in 1987. The scale runs from 1 to 16, the higher the MERV the greater the percentage of particles the filter will capture. The flat throwaway typically falls in the 0-1 MERV range. The pleated throwaway is usually 3-6, and the electrostatic pleated is 8-11.

ASHRAE recommends buying replacement filters with MERV ratings of 6 or higher, but make sure you buy the right filter for your home's system. The higher the MERV rating the more resistance it will have to airflow. A filter that is too dense could restrict airflow or physically damage the heating and air conditioning system.

With more than 300 million disposable heating, ventilating and air conditioning -- or HVAC -- system filters ending up in landfills each year, the industry is looking for other ways to help homeowners maintain high-quality air in their homes without adding to the waste stream.

One company, PollenTec, has introduced an HVAC air filter it says can last up to five years, is washable, is reusable and is easy to clean. Made from a patented spun and coated high-grade polyester, the filter utilizes four cross-directional layers, the first designed to capture all airborne pollens and the majority of other microscopic particles, the second two layers capturing what's left. The MERV 8-plus filter, which takes less than three minutes to clean, is available in nearly three dozen standard sizes.

Even with regular maintenance, it's difficult to keep the average home at a comfortable level. Typically, a central thermostat tells the heating or cooling system to turn on or off. But because each room usually has a different configuration of doors and windows, some rooms may become over-heated or over-cooled. The Activent, another technologically innovative product, allows you to wirelessly control the flow of forced air into your home, room by room, in up to a third of a home's air registers.

After installing the Activent as the new register, users set the desired room temperature using a wireless remote that communicates with a thermostat placed anywhere in the room. It automatically signals the vent to close when the temperature is reached and open when additional heating or cooling is needed. It also can be operated manually.

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