Furnace Filters

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Q: Some time ago I replaced the inexpensive fiberglass air filters in our forced-air heating system with more expensive pleated filters, which I thought would be more effective.

But the person who serviced my system said that the pleated filters add too much resistance to air flow through the ducts, making the system more expensive to operate. Is this true?

Don, Winston-Salem, NC

A: Richard Trethewey replies: You were correct in thinking that those standard spun-fiberglass furnace filters don't help much to improve indoor air quality. The pleated filters that slip into the standard inch-thick filter slot are somewhat more effective, although the ones that are electrostatically charged to attract allergens are far better. Pleated filters add some resistance to the air flow, but if you make sure they're rated for the blower capacity of your furnace, you should be okay. (For more effective filter options, including 3-inch-thick pleated media filters and electrostatic air cleaners, talk to a heating specialist.)

Any filter, pleated or not, will increase operating costs and reduce a blower's performance if you don't change it often enough. That's absolutely the most important thing you can do to keep your system running efficiently.

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