by Michael Finley
The first thing you should consider is a timer instead of a switch. Thesuccess of your fan relies on a two-fold approach. The Home Ventilating Instituterecommends that your fan be capable of achieving 8 air changes per hour, withthe exhaust of air continuing for 20 minutes after use of the bathroom. Using atimer will help you achieve the extra run time without having to remember tocome back and turn it off. Plus with the new quiet fans available it isn'tuncommon to forget to turn a bathroom fan off now because we don't have thatload roar to remind us it is on. To achieve the air exchanges we need tocorrectly size the fan.
- First find the volume of the bathroom. Volume = length × width × height
- Find the CFM (cubic feet per minute). Volume ÷ 7.5
- This CFM is the minimum airflow required to achieve 8 air exchanges per hour.
Example: Volume of the room = 10 × 6 × 8 = 480
CFM = 480 ÷ 7.5 = 64
In this example you would only purchase a fan that has a CFM listed on the boxgreater than 64.
Next comes noise... balance noise against air volume!!
Choose your fan based on how quiet you want it. PersonallyI want the quietest fan I can afford. Ideally you don't even want to know it ison. However, the price goes up as the noise levels go down, so you have to keepyour budget in consideration. Also, the noise level goes up as the speedof the fan increases. A real balancing act!
Bathroom fans are measured by sones, a subjectivemeasurement of how a sound is sensed. A sound that is "grating" orannoying will rate higher in sones than it would in decibels, a more scientificmeasurement.
Here are some examples of sone measurements:
4.0 sones is the sound of normaltelevision (which would be ridiculously loud for a normal bathroom fan, thoughI've heard some this loud!)
3.0 sones is office noise (still veryloud for a fan)
1.0 sone is the sound of a quiet refrigerator(about as good as it gets!!)
0.5 sone is thesound of rustling leaves.
Keep your new quiet fan quiet by installing itcorrectly!
Soafter you spend the extra money on a fan that is quiet, don't make commonmistakes in the installation to negate that low sone fan. Always use screws inthe installation, not nails. Nails will vibrate lose eventually and createnoise. Use 4 inch venting not 3 inch, the bigger the venting the quieter it willbe. Make turns in your venting gradual; avoid 90-degree bends if possible toreduce air noise in the venting.
The only other considerations are features and looks. You can get a fan witha light in it; you can even get a fan with a heating element in it. Looks runfrom just a white grill to just about anything you can imagine. The limits arejust your budget and your tastes. But start with CFM and Sones ratings first,then looks. Doing this will ensure you have a bathroom fan that not only looksgood but is doing its job, which is protecting your bathroom from the perils ofmoisture.
This article provided by Michael Finley of
Rocky Mountain Custom Home Improvements, Inc
