Dear Jim: My bathroom vent fan is noisy and there is a mold problem around the tub, so I think a new vent fan is needed. I want an efficient, quiet one. What features should I look for and how big should it be? – Chris S.

Dear Chris: Most older bathroom vent fans were noisy when new and the sound level increases with age. Bathroom mold and mildew problems are caused by excessive humidity from using a vent fan that is too small or not running it long enough.

Your budget will determine the quality (noise level and features) of the vent fan you select. The top-of-the-line, quietest models with all the latest features can cost up to $200. These very quiet vent fans are ideal for a bathroom in a master bedroom where another person is trying to sleep.

A new lower-cost option, if you just need somewhat quieter operation and more air flow, is a rebuilding kit for about $30. These kits work in many older Broan and Nutone vent fans, which were installed by builders in many homes. The kit includes a modern grille, two motor plates and a new motor.

You have quite a few bathroom vent fan options – fan only, fan-light, fan-light-heater, and fan-light-night light. There are also different types of controls – on-off wall switch, motion-sensing and humidity-sensing.

Humidity-sensing vent fans are most effective and efficient because they come on automatically only when needed and then shut off. This allows you to leave for work without switching off the fan while the bathroom is still too humid. The best models sense the rate of change in humidity as opposed to just overall humidity level. You can manually override the sensor.

Fan noise level is rated in sones, so compare them for various models. The quietest ones are only 0.3 sones, which is barely audible. Special grille designs and large blades, which turn slow more slowly, reduce the sound level. Models designed with a 6-inch duct, instead of the typical 4 inches, are quieter. Installing a remote in-line fan with multiple ports is another quiet option. If you select a fan-light model, get one that uses fluorescent bulbs for greater efficiency. To be Energy Star-qualified, fan-lights must use these bulbs.

Night light options use only about four watts. Another lighting option is a new ceiling recessed fan-light. It resembles a standard recessed light but doubles as a vent fan. Venting tubular skylights for bathrooms are also available. The size of a vent fan is rated in cfm (cubic feet per minute) of air flow. A rule of thumb is you need 1.1 cfm for each square foot of bathroom floor area. Dividing the cfm of a fan by its electricity usage (watts) is a good way to compare their efficiencies.

The following companies offer bathroom venting products: American Aldes, (800) 255-7749, www.americanaldes.com, Broan-Nutone, (800) 558-1711, www.broan.com; Continental Fan, (800) 779-4021, www.continentalfan.com; Fantech, (800) 747-1762, www.fantech-us.com; Panasonic, (800) 211-7262, www.panasonic.com; and Solatube, (888) 765-2882, www.solatube.com.

Send inquiries to James Dulley, Bangor Daily News, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.