Functions of furnace filters and room air cleaners
Q. My kids have allergies year-round, so I need room air cleaners in addition to the main one on the furnace. How do I compare the effectiveness and efficiency of various units?
A. Selecting a room air cleaner can be confusing with all the types, sizes and prices. There are significant effectiveness and electricity usage differences among the units. Depending upon your kids’ allergies, the proper filtration type is more important than the size or price.
Using room air cleaners does not eliminate the main furnace filter. Instead, it removes particles that stay suspended in the air through the ductwork. Using room air cleaners helps indoor air quality and keeps the heat exchanger clean for better furnace efficiency. The amount of electricity used by room air cleaners does not vary much among the designs.
Many of the particles and allergens in room air are relatively large (mold, pollen) so they do not stay suspended long enough to make it to the furnace filter. They puff up each time someone sits on a sofa or bed, so room air cleaners are more effective for removing these.
The Association of Home Appliance Manufacturers (AHAM) has testing standards to rate the effectiveness of different types of room air cleaners. It is called CADR (clean air delivery rates). Those rates allow you to compare the efficacy without considering the design or the type of filter material.
First, check with your allergist to determine which allergens are causing the most problems for your kids. Knowing which ones to remove from the room air is essential because the particle size varies significantly for various allergens.
The CADR rating tests are done for the three most common particles in the air — household dust, tobacco smoke and pollen. Most allergens are in this range of particle sizes. Each air cleaner will have three individual rating numbers, one for each particle of the above measures. A good filter for pollen may not be very effective for smoke.
To use the CADR rating when selecting a model, calculate the room’s square footage and multiply it by 0.67. For example, if you need to remove pollen from a 10 x 12-foot bedroom, the room air cleaner should have a CADR pollen rating of 80 or higher.
If you are not sure which particles you want to remove and generally want cleaner room air, a model with a HEPA filter and a carbon element (also removes odors) is an excellent overall choice. In addition, a multiple-speed model for rapid filtering or for slow, quiet operation at night is a plus.
The following companies offer room air cleaners:
• Blueair, (888) 258-3247 blueair.com
• Holmes, (888) 546-5637, holmesproducts.com
• Honeywell, (800) 447-0457, honeywellpluggedin.com
• LakeAir, (800) 558-9436, lakeair.com
• Whirlpool, (866) 698-2538, whirlpool.com
Q. Our old concrete patio is crumbling and needs to be replaced. It got pretty warm in the summer sun. What do you think about putting in pipes when the new patio is poured to preheat the incoming water?
A. Your basic idea of preheating the incoming water, so your water heater runs less makes sense. However, concrete’s high heat capacity and relatively poor thermal conductivity would not be very effective.
A better choice is to make some solar collector that gets hotter in the sun and transfers more heat to the incoming water. Make sure to install valves to bypass it during the winter.
Send inquiries to James Dulley, Arkansas Democrat-Gazette, 6906 Royalgreen Drive, Cincinnati, OH 45244; or visit dulley.com.