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Choosing a bathroom fan

Proper bathroom ventilation ensures that stale air and excess humidity is expelled. High performance and quieter than ever, today’s bathroom fans are available in various sizes, with or without light fixtures, high or low-capacity, and with manual or automatic controls. Here is what you need to know to choose the fan which best suits your needs.

Understand the needs

Ask yourself the following questions to understand your actual requirements.
  • What is the total area of the bathroom?
  • How many installations does your bathroom include (shower, bathtub)
  • How long will the exhaust duct be?
  • Should the fan be equipped with lighting?
  • Will the housing be installed in the attic or in the ceiling?

Fan types and models

Bathroom fans are considered as air extractors. They expel stale and damp air outside without bringing fresh air in, and are very effective when they are the right size for the room.

Nowadays, all new bathrooms must be equipped with a ventilation system in compliance with the building code.
There are two main categories of bathroom fans:
  • Ceiling insert: The ceiling insert is the most popular model and easiest to install, and because hot, moist air rises, it performs well. May include a lighting fixture or heat lamp.
  • Inline: This is a very quiet fan as the fan assembly is located in the attic or crawl space. Although this type of installation is less common, an inline fan can be connected to more than one grille housing.
All bathroom ventilation systems operate with either a propeller or turbine fan.
  • Axial extractor fan (propeller) has blades that move the air in a way that resembles an airplane propeller.
  • Centrifugal fan (turbine) has a rotating cylinder with straight blades, a little like a hamster wheel. This type of fan is quieter and more effective than the propeller fan. It effectively draws in air which is exhausted through the ductwork, unlike the axial extractor model.

A few important features

The bathroom ventilation system includes a fan and an exhaust duct to the outside.

Fan capacity

Before you purchase a fan, determine the power you need to effectively ventilate your bathroom. There is a simple rule to follow: calculate 1 cu.ft./min for each sq.ft of surface area. We recommend you add a 20% margin, and add 1 cu.ft./min for each linear foot of rigid ducts and 2 cu.ft/min for flexible ducts.
For example: a bathroom measuring 10'x10' ventilated through a 6' flexible duct will require a fan capable of generating 100 cu.ft./min (10x10) + 20 cu./ft./min (20% of 100) + 12 cu.ft./min (6 x 2) = 132 cu.ft./min of ventilation volume
A smaller bathroom will require a fan capable of generating ventilation volume of at least 50 cu.ft./min.

If you have a whirlpool bath or multi-jet shower in your bathroom, you should have a fan capable of generating at least 250 cu.ft./min of ventilation volume, because the increased movement of hot water will produce a lot of moisture in the air.


Ventilation ducts can be either flexible or rigid. Flexible ducts are recommended for distances less than 16'. They are also adaptable and can be navigated through any number of obstacles. Opt for insulated flexible ducts. The smooth surface of rigid ducts facilitates air circulation which is why it is recommended for longer distances.
Shorter ducts mean better air circulation and reduced power requirements. We recommend using ducts that are at least 4" in diameter. Longer ducts should be 6" in diameter which will facilitate the movement of air. Smaller ducts, 3" in diameter, are not recommended.

Noise level

Fan noise is measured in sones, and bathroom fans are assessed when they are operating at maximum capacity. The higher the sone rating, the louder the fan. Fans noise varies from less than 1 sone to 4 sones. A fan with a noise level of 2 sones is considered silent.

Activation and operation

Fans can be activated by a standard switch, timer, motion sensor or humidity sensor.
  • Standard switch: with a standard switch, the fan is activated with the same switch as the main light switch in the bathroom. You avoid the nuisance of two switches and you can be sure the fan will be turned on as soon as someone enters the bathroom.
  • Timer: a wall timer is used to set the power in “On” mode and to select the running time of the fan.
  • Sensors: fans can be activated by motion or humidity sensors for a predetermined period of time, or only when there is movement or humidity present in the room.


Check the space you have available before you select a fan. Because the fan is usually secured to the attic frame or to the ceiling, ceiling height may be a factor for a ground floor or basement bathroom.


Fans with integrated lighting are very practical in small bathrooms. You can also find fans that include a heat lamp, which can be very welcome when you step out of the bath or shower. Some models offer low-wattage night lights, which is useful for the children's bathroom.

Grille or protective cover

The grille is usually made of plastic and can be square, rectangular or circular in shape. It fastens to the housing and can be removed to facilitate installation and maintenance.


When you are determining the location of the fan, take into account that the housing must be solidly secured to floor joists in the attic. Fans are typically installed on the ceiling in the middle of the room, or depending on the model, directly above the shower or bathtub with a ground fault circuit interrupter (GFCI protected).
The fan can also be installed on the bathroom wall; this type of installation is less effective since heat and moisture rises. If the toilet is located in an enclosed space, you should also consider installing a fan there.
Ductwork is concealed in the ceiling, attic or crawl space and vented to the outside. Ductwork must be installed lying horizontally, sloping downwards slightly so that any accumulated water can easily drain out if condensation occurs. You want to properly insulate your ventilation system and apply caulk where necessary to guard against heat loss. If your fan installation is part of a renovation project, existing plumbing and electrical work may influence the path the ducting needs to follow.
Unless you are very experienced in electrical work, it is highly recommended that you call upon a master electrician to connect your new fan. Remember that in Quebec, all electrical installations must be carried out by a master electrician and member of the Corporation des maîtres électriciens du Québec (CMEQ).
Furthermore, call upon qualified professionals if you prefer not to do it yourself.

Expert tip

Never vent to the attic; always vent to the outside. Heat and moisture will produce rot and mould in materials such as wood and insulation.


When in operation, fans generate static electricity which leads to an accumulation of dirt and sometimes even mould on the fan and fan housing. It is important you clean your ventilation system regularly, including the fan, fan housing, exterior exhaust outlet and any other accessible components of the system.
Cleaning a bathroom fan is fairly straightforward: disconnect the power first, then lower the grille housing and remove the module. However, cleaning an inline installation with ductwork that is harder to access can be more difficult.