How *I learned about furnace filters

My office has a window that looks out on the roof of Godwin's Division Avenue hardware store. Imagine my surprise when I saw someone walking around out there recently! Ever curious, I climbed out my window and joined Steve McCalmont, one of Godwin's heating & cooling techs. He was replacing the filters in our building's A/C units - and proceeded to teach me the importance of furnace filters.

Filters aren't just about clean air - although that's important. Clean filters keep the motor from working too hard, stressing out, and failing prematurely. "You know how by the end of summer a fan's blades are all coated with dirt and the fan goes 'whirr, whirr'?" he asked. "It's making that sound because it has to work so hard with all that crud on it." And the motor in our furnaces and central air units are faced with the same challenge when they try to push air through a dirty filter.

Bottom line: Changing the filters often can add "5 or 6 years" onto the life of our furnace, says Steve.

How often should we change furnace filters?

• Every 2-3 months under normal conditions.
• Monthly if there are pets, smokers or people with extensive or multiple allergies.
• Monthly if our homes are poorly insulated - extra air brings in extra particles.
• Check the filter every week or two if there's any construction going on. We know that construction dust gets everywhere - and filters catch a lot more than we see.

MERV (Minimum Efficiency Reporting Value) rates how much stuff a filter will remove from the air (see chart at right, click it to see a bigger version). Numbered 1-16, the higher MERV ratings filter more stuff. But higher isn't necessarily better. Some furnaces don't have the power to force air through a denser filter - leading to premature failure of the furnace motor. Conversely, a low MERV-ranked filter may not keep enough stuff out. Check the owner's manual.

Then there's type:

• Non-pleated filters are usually made of polyester or fiberglas. The flat design means that they can't catch as many particles - and they're becoming obsolete anyway. (Steve's take on non-pleated filters? He pretty much rolled his eyes.)
• Pleated filters are accordion-like and therefore have more surface area to catch stuff. The accordion design also allows air to flow more freely.

Most furnace filters are under $5. When we keep a few in the house, we're more likely to change them more often, so buying a years' worth is a good idea. Of course, Godwin's three hardware locations (GR, Ada and Wyoming) have furnace filters - and products to help seal and insulate our homes.

For more extensive maintenance, Godwin Heating & Cooling techs - including Steve - have an average of 12 years experience. Call us at 243-3131.

 *I'm Juliette Cowall, marketing director of Godwin.