Is your Bathroom Exhaust Fan working efficiently?

Is your bathroom exhaust fan ACTUALLY pulling the humidity out of the bathroom or is it just making a lot of noise?

Common Mistake Made

Whenever we are asked to provide a quote for a bathroom renovation, we often ask the home owner if they have a functioning exhaust fan. It is the most common overlooked item in a bathroom renovation. The most common answer we get is,

It’s working just fine! Turn on the switch and listen.

However, just because your fan is making noise, doesn’t mean it is even “working” at all!

Whenever we are hired to do a home inspection for a potential buyer, one of the tests we do is our “toilet paper test” to ensure the exhaust fan is truly working. Unless the motor stops functioning completely, your fan will still make noise even if it’s not sucking any of the moisture out of the room. This can often be the reason why your paint will start peeling from your ceiling or walls in the bathroom.

At this time of year we typically don't open our bathroom windows to let the moisture and humidity out from our showers in the morning. Consequently we might be leaving our exhaust fans running longer than usual.

Toilet Paper Test

We recommend doing a toilet paper test to ensure your fan is functioning effectively. Take 2 pieces of toilet paper. Turn the fan on and put the toilet paper up to the fan. The fan should suck the toilet paper up and it should stay attached to the fan. If it doesn't, all your fan is doing is making noise. It's not actually sucking out any of the humidity.

How to Fix the Problem

The first thing to try is washing the fan and the motor. Remove the trim from the fan and wash it thoroughly. Next, unplug the motor and remove the motor completely. Submerse it in warm soapy water and clean it thoroughly. Take it out, rinse and let dry for 48 hours before plugging it back in again. Use a vacuum or damp cloth and be sure to clean inside of the housing prior to plugging it back in.

Try the toilet paper test again. If it holds this time, all you needed to do was clean the motor. If it still doesn't hold, it's time for a new exhaust fan.


Why You Need a Functioning Exhaust Fan in your Bathroom

Bathroom exhaust fans are an important part of a home’s ventilation system. They eliminate odours, improve indoor air quality, and remove moisture and humidity that can lead to structural damage or mildew and mold growth. Unless a bathroom is properly ventilated, the moisture from a shower has no place to go and can penetrate into drywall, attic insulation and structural joists. If a mirror is steamed after a shower, or there is a build-up of condensation on bathroom walls, it may be time to service or upgrade the bathroom fan.


How to Select the “Right” Exhaust Fan

Canada Mortgage and Housing Corporation (CHMC)’s research shows that many bathroom fans across Canada should be replaced or serviced due to inadequate airflow, inability to overcome static pressure, high leakage rates and generally poor condition. 

There are several factors to be considered when selecting a new or replacement bathroom fan: airflow rate, sound levels, energy efficiency, and aesthetics and fan control.

Air Flow rate

The Home Ventilating Institute (HVI) has provided guidelines for the proper ventilation of a bathroom. For bathrooms under 100 square feet, the basic rule is to exhaust a minimum of one cfm (cubic foot per minute) for every square foot of bathroom area. So an 8’ x 10’ bathroom, 80 square feet, would have a minimum airflow requirement of 80 cfm. For bathrooms over 100 square feet, the calculations are based not on square footage, but on the number and type of fixtures in the bathroom. An allowance of 50 cfm should be made for each standard toilet, bathtub and shower. Allow 100 cfm for whirlpools and hot tubs. For example, a bathroom with a hot tub, shower stall and toilet would require a minimum of 200 cfm (100 + 50 + 50).


Air make up is an important factor to consider when sizing a bathroom fan. Fans will only remove air from an area at the rate that the air can be replenished, regardless of the correct sizing or rated air flow. In many cases, the space between the bottom of the door and the floor is adequate, but in some cases an additional air make-up source must be installed to allow the fan to operate at peak performance, such as an additional grille installed in the bathroom door.

Sound Level

The second issue is the sound level of the bathroom fan. Various studies have shown that many people do not turn on their bathroom fans because they are too noisy. When considering fan sound levels, it is important to check for the HVI rating. If a bathroom fan does not carry an HVI rating, there is a very good chance that the fan will be noisy. Sound is rated by sones and the higher the number the louder the fan will be. A good rating to look for is 1.5 or lower. Be careful not to get one that’s too low otherwise you might forget that you left it on.

A quiet alternative to traditional bathroom fans is the remote mounted in-line ventilation fan. These fans are mounted in the attic, thereby removing the motor and fan assembly from within the bathroom itself, and provide quiet and effective exhaust ventilation to deal with most airflow requirements. By removing the fan assembly from the bathroom space and mounting it remotely, the possibility of the ultimate in quiet operation, virtually 0 sones, can be achieved (depending on how far away the fan is mounted). We again caution that some of our customers have left these fans on all day because they couldn’t hear them running and forgot about them.

Energy Savings

With energy savings being on everyone’s mind, choosing an Energy Star fan is, without question, the best choice. More than half of the fans operating in Canada today are not energy efficient models; in fact, some fans in operation today are using more than 180 watts of power. A retrofit of the bathroom fan can lead to savings in the electrical bill and increased performance of the bathroom fan.


Fan Control

This is an important aspect of the ventilation process, and is something that should be strongly considered.  CMHC and HVI both suggest that a bathroom fan run for a minimum of 20 minutes after a shower, to allow for the removal of excess humidity and moisture.  Many bathroom installations have the fan controlled by the same switch as the light, resulting in the fan being turned off as soon as the occupant leaves the room.  It is recommended that a separate switch control the fan or, better yet, a timer that allows the fan to run for a pre-determined amount of time after showering.

Did this blog post inspire you to check the efficiency of your exhaust fan? If so, leave us a comment below what the outcome was and how you found the post to be helpful. We’d love to hear from you.

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