Dear Jim: I know it is important to run our bathroom vent fan, but I seldom switch it on because it is so noisy. We are remodeling our bathroom now. What are the best new vent fans and what size is best? — Kathy J.

Dear Kathy: Running a bathroom vent fan is important for indoor air quality (moisture, odors, allergies) and to keep your utility bills low. Even if your bathroom has a window that you can open, running a vent fan is more efficient. It provides better control over the ventilation and energy loss.

Consider installing a super-quiet combo vent fan/light. The most quiet, premium models are also usually the most decorative, full-featured models. Look for beveled or frosted glass and polished metal with real oak trim. The vent air inlets are hidden in the decorative trim.

For the greatest convenience and efficiency, select one of the many models with automatic humidity and motion sensors, plus a night light. Some new models use efficient compact fluorescent bulbs that last 10 years or more.

The humidity sensor runs the bath vent fan only as long as necessary. It quickly clears excess moisture and then shuts off to save electricity. It also does not suck excessive air (already heated or cooled) out of your house.

A motion sensor and night light are a great plus. The 7-watt night light uses very little electricity and is adequate brightness at night. The motion sensor for the bright light is ideal for children who tend to forget to switch off the light. There is also a switch to override the sensors.

When shopping, many vent fans will look similar. Compare the sound level ratings (in sones). Some small quiet models are under 1.0 sone (like a quiet whisper). The sound level usually increases with greater air flow capacity.

Internal design features make the difference between a noisy and a quiet fan. Special sound absorbing scrolls and flexible motor mounts reduce noise. Just the design of the interior air chamber has a major effect.

Another option to consider is a remote in-line vent fan. The fan motor is located far up in the attic with ducts running down to attractive ceiling air inlets. With the fan motor in the attic, it is very quiet.

A single powerful remote vent fan can vent two bathrooms with a separate duct to each bathroom ceiling. For effective ventilation of one bathroom, install two air inlets (one over the lavatory and one in the shower).

As a rule of thumb, the air flow capacity (in cubic feet per minute or cfm) of a bathroom vent fan should be about 10 percent greater than the square footage of the bathroom. A 50 square foot bathroom needs a 55 cfm vent fan.

Write for (instantly download — www.dulley.com) Update Bulletin No. 427 — buyer’s guide of 12 quiet bathroom vent fan/lights, air flow, sound levels, features and a sizing chart. Please include $3.00 and a business-size SASE to James Dulley, Bangor Daily News, 6906 Royalgreen Drive, Cincinnati, OH 45244