Clearing The Air: Everything About Bathroom Ventilation – On the House

Clearing The Air: Everything About Bathroom Ventilation

By on June 12, 2015
Cleaning Bathroom Vents

During a bath or shower, the humidity level in a bathroom can be like that in a tropical rain forest – uncomfortable, hot and damaging – a perfect breeding ground for mold, mildew and microorganisms that can impact your health. It cracks and peels paint, ruins gypsum wallboard, causes exterior paint failure, warps doors and rusts cabinets and fixtures. Without control, it can even cause deterioration of joists and framing above the bathroom. As it condenses on windows, walls, ceilings and cabinets, it attracts dirt and makes more frequent cleaning and decorating necessary.

Exhaust fans, ducted to the outside, remove moisture and prevent these types of problems in bathrooms. Not only will occupants be more comfortable after a bath, shower or spa, but the room will also be rid of odors, potentially hazardous aerosol vapors and other pollutants. In addition to healthier air, this minimizes the potential for home damage, saving the homeowner the cost of making repairs to correct problems that were simply preventable.

Interestingly, the building code does not require a fan to be installed in a bathroom that has a window. We think that this is a big mistake. Moreover, where a fan is required, the code only calls for one powerful enough to produce five air changes per hour. The Home Ventilating Institute (HVI), an industry trade association, suggests a more aggressive rate of eight complete air changes per hour. For most bathrooms this works out to one CFM per square foot of bathroom area (70 CFM for a 7 x 10 bathroom), but a minimum of 50 CFM is required even for small bathrooms.

Cost-conscious builders often focus on one of two ready solutions to meet minimum requirements in producing a code-worthy house: (1) they simply install an operable window in baths with an exterior wall, or (2) they install a bathroom exhaust fan that meets minimum air-exchange requirements.

So, what’s wrong with just opening a window or running a cheap and noisy, builder-basic bathroom fan? It’s where serious problems can – and often do – begin. Allowing fresh air in through an open window can be marvelous on a lovely spring day. However, few people open their bathroom window at five or six o’clock in the morning as they prepare for work on a cold winter’s morn. This is also compounded by a number of issues, starting with “tighter” sealed homes resulting from the energy-efficiency drive kicked-off in the 1970s. And there is the safety and security issue. Do you want an open window while showering? Or to leave it open for an extended period to dry things out? Probably not. Thus, the “open window” technique is not the best solution. Consequently, moisture from bathing remains trapped and results in mold, mildew, peeling wallpaper and potentially rotted insulation and framing. What’s more, the “open window” solution simply does not provide enough air exchange – fast enough or thorough enough – to provide the moisture evaporation needed to eliminate the potential problems just noted.

Then there is the cheap and noisy, builder-basic bathroom fan. Because it is noisy, homeowners use it as little as possible. Some go so far as to unplug the fan motor in the housing. And when it is used, for whatever time period, if improperly installed – vented directly into the attic – they are simply speeding up the process of transferring lots of destructive moisture-laden air directly from the bath to the vulnerable interior structure where it can become a full-blown science experiment.

So what’s a homeowner to do? First and foremost, be sure your current bath fan exhausts outdoors. Next, be sure you run your bathroom fan long enough to make sure it provides sufficient air-exchange to dry out your bathroom, which can take as long as 20- to 30-minutes.

Still “better” solutions are: (1) A bathroom fan upgrade kit – available for some popular brands at home centers – that easily replaces earlier less efficient, noisy models with a more powerful, quieter motor and that includes a new face-plate grill for an updated look… and/or (2) Install a light switch with a built-in timer that can be set to shut off the fan after a given period of time. Either is good, together they’re great.

However, the “best” solution is to look to today’s new breed of bathroom ventilation solutions that are: quiet, powerful, well-vented and loaded with make-sense conveniences. Today’s best bathroom exhaust fans are either very quiet or “whisper” quiet – meaning you don’t hear them at all. The noise level of bathroom fans is measured or rated in “Sones.” Without going into a lengthy scientific explanation, just know that typical fans operate at 4.0 to 6.0 Sones, which is pretty noisy.

Newer, quieter models (and upgrade kit motors) operate at about 3.0 Sones, which is far easier on the ears. High-end models, with new hi-tech super-quiet motors or with fan motor boxes installed in remote locations drop Sones to miniscule levels in the .09 to .03 range.

Some brands also offer contemporary larger diameter ducting, up to 6-inches, which reduces noise caused by exhaust resistance. The larger ducting improves performance versus the industry average 4-inch ducts or the totally inadequate 3-inch venting used on the builder-basic models.

Beyond this, are all the nifty amenities that make life just a little bit better. They include things such as: fan/light combinations with built-in ceiling lights and/or soft-glow night lights; fans with both lights and built-in heaters; and fans with “humidity sensors” that automatically turn on when needed and off when their job is done.

If we’ve simply made you realize your bathroom fan is for more than just “clearing the air,” it’s a great start. But if you’re tired of seeing fogged-up mirrors, drooping wallpaper, peeling paint, nasty mildew and scary mold, then it’s time for action.

Practice “good” ventilation by running your existing fan long enough to do the job for which it is intended. In addition, consider stepping-up to “great” ventilation by heading for your local home center to check out today’s state-of-the-art “quiet” bathroom ventilation. Just remember to check the sone rating for quietness and the CFM rating for the volume of air-exchange. Remember, the lower the sone rating and higher the CFM rating, the better the fan.

Here’s hoping that we’ve helped “cleared the air” on bathroom ventilation in your home.

For more home improvement tips and information search website at  or call our listener line any time at 1-800-737-2474! All you need to do is leave your name, telephone number and your question.

About onthehouse

You must be logged in to post a comment Login

Leave a Reply

Pin It on Pinterest