Furnace filters 101

Changing your furnace filter is the easiest way to take good care of your investment. Find out what to look for the next time you head to the store to buy a furnace filter.

Types of furnace filters

Furnace filters are not created equal – especially if you have allergies, asthma or other respiratory problems.

Disposable and washable filters

If allergies and respiratory problems aren’t a concern for your family, a disposable or washable filter can be enough to keep your furnace clean. But it’s important to change or clean the filter every month – remember that dust and dirt are the cause of half the repair calls to service technicians!

Disposable fiberglass filters are the least expensive – and also the least effective, designed to block only large dust and dirt particles to protect your furnace. Smaller particles, like pollen and mold, pass right through.

Washable “electrostatic” filters have a static charge that attracts dust, dirt and other matter. These filters are slightly more effective than disposable, but still block only 15 to 20 percent of airborne particles.

Pleated filters

Pleated “allergy” filters use a much denser mesh material to trap particles. The pleats increase the surface area, eliminating large allergens like pollen and mold – most are 35 to 50 percent efficient.

A pleated filter is a cost-effective option for reducing allergens. These filters cost around $5-$15 each, but are designed to last up to three months. A high-efficiency pleated air filter costs around $250 to $450.

Electronic air cleaners

Electronic air cleaners use electrodes to create an ionized electrical field that “magnetizes” pollutant particles and collects them on the filter material. An electronic unit can eliminate virtually all pollen and mold spores, up to 94 percent of smaller particles, and even up to 80 percent of airborne viruses.

Electronic air cleaners are expensive, ranging from $650 to $850, but they’re the best at removing harmful particles and pollutants from the air. In many cases, the initial cost can be offset with lower medical bills.

Keep the blower fan running

No matter what type of filter you choose, it will work best if you keep the blower fan running continuously.

According to Home Energy Magazine, if the fan is set to “auto,” it’s running only 20 percent of the time – meaning your furnace filter will trap only 20 percent of the 50 percent of the particles it’s designed for – resulting in only a 10 percent overall efficiency.

Setting the fan to “on” will also help keep air circulating through your home, preventing the warm air from rising and pooling near the ceiling and increasing your comfort.