Your No. 1 fan by Steve Maxwell Sept. 20, 2008 Toronto Star

Is your exhaust fan noisy and seemingly useless? You're not the only one plagued with this problem, and manufacturers everywhere are improving exhaust fan designs.

Quiet and powerful models are coming out in various configurations, including designs made especially to replace inadequate existing units or to install fans in new locations. But before you avail yourself of any of this superior technology, you need to begin with a simple but crucial calculation.

To be effective, a bathroom fan needs to change all the air in your bathroom at least eight or nine times an hour. Ten is even better. Any slower than this and excess moisture will probably damage walls, ceilings and windows before it's drawn outdoors.

Determine the size of fan you need by calculating the total volume of your bathroom (length times width times ceiling height in feet). Set this number aside for a minute, then look at the fan.

All exhaust fans are rated in cubic feet of air moved per minute (CFM), so you'll have to multiply this number by 60 to get an hourly figure. Can the fan you're looking at move at least eight times the total volume of air in your bathroom in 60 minutes? If not, you need a bigger fan. Standard bathroom exhaust fans only work properly in the smallest of bathrooms. If you've got anything larger than an ordinary bathroom, you definitely need a larger-than-ordinary fan.

The other issue to consider as you make a choice is noise output. Larger fans are slightly louder, though you should never go for a quieter fan that's not big enough. Even today's largest bathroom fans generate a background sound somewhere around one "sone." This is a unit of sound output used across the board in the exhaust fan industry, and a one-sone rating is quiet indeed .

I recently installed a bathroom fan in a brand new location and the unique shape of the unit made the job much easier. It was a Panasonic WhisperFit model designed especially for retrofit situations. The unit is thinner than comparable fans for new construction, with a housing depth of 5  5/8-inches versus 8 inches for standard designs.

One of the biggest challenges when installing an exhaust fan where none existed before is electrical supply. It's one thing to cut a hole in the ceiling and route new ducts, but it can be very disruptive to cut into your walls to reroute wires and install a switch. An easy way around this is to tap into an overhead light fixture to power your new exhaust fan. It's usually a matter of running a few feet of new cable to the fan itself. This approach also eliminates the need to install a new wall switch – your exhaust fan comes on and off with the light.

The difference between a properly selected and installed bathroom fan and the kind that's found in most Canadian homes is startling. Take the time and trouble to cover the important details and you'll enjoy a quiet and effective installation.

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