Bathroom fans help keep humidity at bay

Hey there, time traveller!
This article was published 18/03/2007 (6887 days ago), so information in it may no longer be current.

DURING a bath or shower, the humidity level in a bathroom can be like that in a tropical rainforest — uncomfortable, hot, damaging and a breeding ground for mould and mildew.

This humidity cracks and peels paint; ruins gypsum wallboard; causes exterior paint failure; warps doors and rusts cabinets and fixtures. As it condenses, it attracts dirt and makes more frequent cleaning and decorating necessary. It can even cause deterioration of joists and framing above the bathroom.

Exhaust fans, ducted to the outside, remove moisture and prevent such problems. Not only will occupants be more comfortable after a bath, but the bathroom will also be rid of odours.

But you need to have the correct kind of fan, and there are many new models on the market that can help you get the job done the right way.

The federal Uniform Building Code does not require a fan to be installed in a bathroom that has a window. Moreover, where a fan is required, the code calls only 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. Check that the fan you install is strong enough for the size of your bathroom. Fan strength is measured in cubic feet per minute (CFM), and you’d need a 70 CFM fan to handle a 70-square-foot bathroom, and so on. Note that a minimum of 50 CFM is required even for small bathrooms.

But cost-conscious builders often skimp in this department and do one of two things: install an operable window in baths with an exterior wall, or install a bathroom exhaust fan that only meets minimum air-exchange requirements.

So, what’s wrong with just opening a window or running a cheap and noisy, builder-basic bathroom fan?

Allowing fresh air in through an open window can be marvellous on a lovely spring day. However, few people open their bathroom windows at five or six o’clock in the morning as they prepare for work on a cold winter’s morn.

Consequently, moisture from bathing can remain trapped.

What’s more, the open-window solution does not provide enough air exchange — fast or thorough enough — to produce the moisture evaporation needed to eliminate the potential problems previously noted.

Then there is the cheap and noisy, builder-basic bathroom fan. Because it is noisy, homeowners use it as little as possible.

Even when it is used, for whatever time period, if it has been improperly installed — i.e. vented directly into the attic — it simply speeds 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, be sure your current bath fan exhausts outdoors, not into your attic. It should exhaust through a duct that terminates at the roof or through an exterior wall. You could fix this yourself or hire a sheet-metal or repair contractor to do it. The cost will vary locally.

Next, run your bathroom fan long enough to provide sufficient air-exchange to dry out your bathroom; this can take as long as 20 to 30 minutes.

Still better solutions are:

* A bathroom fan upgrade kit, available for some popular brands at home centres, that easily replaces earlier, less-efficient, noisy models with a more powerful, quieter motor and includes a new faceplate grill for an updated look. These come priced about US$50.

* And/or installing 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.

The best of these bathroom exhaust fans are either very quiet or “whisper” quiet — meaning you don’t hear them at all.

Some brands also offer larger-diameter ducting, up to six inches, which reduces noise caused by exhaust resistance. This larger ducting performs better than the industry-average four-inch ducts or the totally inadequate three-inch venting used on builder-basic models.

Beyond this are many nifty amenities, including 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.

In general, if you are a homeowner who’s handy you could tackle such installations yourself. Otherwise, have a heating-ventilation or small-repair contractor or an electrician do it for you.

–Associated Press