QUESTION: I am having a new furnace and air-conditioning system installed. The contractor is recommending an air cleaner instead of just the standard filter. Is installing one worth the extra cost and which are best?ANSWER: The answer to your first question depends upon your particular family and its clean air needs. Installing an air cleaner on your furnace will improve indoor air quality. If your family has allergy problems or an activity in your home generates much dust, then an extra cost is justified.Installing an air cleaner can also maintain the highest efficiency level for your heating/cooling system. All air cleaners are mounted on the return air side so they remove the dirt from the air before it enters the blower.Clean air reduces the dirt deposits on the heat exchanger surfaces so heat is transferred more efficiently. This is most important when air-conditioning because the cooling coils get damp and the particles stick and build up.If you don't install an air cleaner, be careful about installing so-called "air cleaner filters" which slide into the one-inch filter slot. They are inexpensive and are better than a filter, but they may increase the air flow resistance above the furnace manufacturer's recommendations as they get dirty. This can reduce the air flow and furnace/air conditioner efficiency.There really is not one best air cleaner for all needs. Most are effective for larger particles and others are better at removing finer particles such as smoke. The basic types to consider are electronic, pleated media and self-charging electrostatic.With any of the above air cleaners, you may consider installing an ultraviolet (UV) light air purifier. The intense UV rays generated inside the air duct kill many bacteria and viruses. This is harmless to people because the light source is totally enclosed in the duct. A UV purifier does not remove particles from the air.Electronic air cleaners are effective for removing even the smallest particles and they consume little electricity. The elements slide out for easy cleaning in a dishwasher and they do not create much air flow resistance. I prefer this type and use one in my own home.Pleated media models use a thick element to mechanically clean the air.They are very effective for larger particles (mold, pollen, dander) which often cause allergies. Replace the element regularly so the air flow does not become restricted.Self-charging electrostatic models are the least expensive and slide into the standard filter slot. These clean the air by creating a natural static charge so dirt particles stick in them. Rinse them off once a month with a garden hose or in the bathtub to release the dirt particles.The following companies offer whole-house air cleaners: Aprilaire (608-257-8801 www.aprilaire.com), Dust Free (800-441-1107 www.dustfree.com), Home Health Products (866-765-1587 www.airhealth.com), Lakeair International (800-558-9436 www.lakeair.com), and Trion (800-884-0002 www.trioninc.com).Send inquiries to James Dulley, Butler Eagle, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com.

QUESTION: We have lived in our house for about 10 years. I recently went up into the attic to store some things and noticed some greenish mold. We have soffit vents. What could be causing the mold to grow?ANSWER: The only thing that will allow mold to thrive is moisture. It could be coming from a slow leak in the roof. The leak may be slow enough that you don't see dripping water but the lumber stays damp.It may also be caused by a lack of adequate attic ventilation. Inlet soffit vents alone are not enough. You also need to have outlet air vents near the top of the roof. These can be individual vents or a long ridge vent.