Exhaust Fan Buying Guide

Bathroom and kitchen fans are an important part of your home’s ventilation system. They remove odours from your house, which improves indoor air quality. They also remove moisture, which decreases the level of humidity in your house. High humidity can damage building materials and can cause mold growth. Mold may affect your family’s health.

COMMON FAN and EXHAUST SYSTEMS

The two most common types of fans are impeller fans and blower fans. Impeller fans move air with blades similar to airplane propellers. Blower fans look like hamster wheels – they are often called squirrel cages – and generally do a better job of moving air than impeller fans.

Most exhaust systems consist of an exhaust fan, ducting and an exterior hood. Some houses have a central exhaust system, in which one fan draws moisture and odours from several rooms of the house using a network of ducts.
Kitchen exhaust systems usually have the fan and fan motor in the exhaust hood. Other systems use an in-line fan, which is in the exhaust duct, or a fan outside the house. In-line and outdoor exhaust fans are usually quieter than systems with the fan in the room. A heat recovery ventilator (HRV) also exhausts moisture and odours. An HRV is a self-contained ventilation system that provides balanced air intake and exhaust. Like a central exhaust fan, it can be connected to several rooms by ducting.
How Do I Choose the Best System?

  • Choose the quietest, most energy-efficient fan in the size range required and also look at the noise that is produced. Look for a fan with replaceable parts and permanent lubrication. A fan suitable for continuous use is preferable. Be prepared to pay more for a quality fan.
  • Select low-resistance (smooth) exhaust ducting. Seal the joints and insulate sections that run through unheated spaces.
  • Place the exhaust hood where it will not cause moisture damage on exterior surfaces.
  • If you have heating appliances with chimneys, make sure that fans won’t cause the appliances to backdraft.
  • Install the proper controls.

Bathroom Fans: What Should I Look For?

Fan exhaust capacity is rated in litres per second (L/s) or cubic feet per minute (cfm). A normal bathroom needs a good-quality fan that draws 25 L/s (50 cfm). A poor-quality fan won’t exhaust enough air and will be too noisy for regular use. The best fans have sound ratings of 0.5 sones or less and consume about 20 watts. Older units typically run up to 4 sones and 80 watts.
Large bathrooms, or those with bigger fixtures, such as spas, need larger fans. Place a bathroom fan as close as possible to the source of the moisture or odour.
Some bathroom fans have lights or heating lamps. If you choose a fan with integrated lights, look for efficiency. Any fan installed in an insulated ceiling for instance, if the attic is above the bathroom ceiling – must not leak air and must be rated for use under insulation.
Make sure that exhaust fans, lights and heaters in bath or shower enclosures are rated and approved for wet conditions. Newer units approved for wet conditions may include ground fault protection.

NOISE

Noise determines whether people use a fan. Many people won’t use a noisy fan. Select the quietest fan in the size you need. Look for fans labeled ‘low noise’ or ‘quiet,’ and check for the HVI rating. If it is not rated, there is a good chance that it will be noisy.

FAN POWER REQUIREMENTS AND AIRFLOWS

There is more to energy efficiency than selecting an energy-efficient fan. Ducting can affect fan performance. Uninsulated, undersized, or droopy flex ducting, ineffective or dirty backdraft dampers and exhaust louvres can cut rated airflow by more than 50 per cent. To find out if your exhaust fan is drawing air, hold a piece of toilet tissue up to the grill. The exhaust air should hold the tissue tightly to the grill. You could also check the outlet to make sure the air is leaving your house.

CONTROLS

Bathroom fans connected to light switches start running when the light is turned on. Often, users turn the light off before all the moisture is exhausted after a bath or shower. An electronic timer, which is usually quieter than a mechanical timer, offers a wide range of settings. Make sure the time instructions are easy-to- understand and the timer is easy to use. You can use motion or humidity sensors, or a combination of both, to control the fan. Controls which allow you to specify operating times or maximum humidity levels are preferable to those where the operation is pre-set by the manufacturer. Use a delayed fan shut-off to keep the fan running for 15 minutes after you leave the room.

CLEANING

Fans create static electricity which attracts dirt like a magnet to the fan and its housing. The dirt can encourage mold growth and restrict air movement. Clean fans, housings, backdraft dampers and exterior flaps seasonally. A typical bathroom fan can be cleaned by pulling down the grill, and unplugging and removing the fan module. Fans in ducts and exterior fans may be difficult to clean.

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