About Your House
The Importance of Bathroom And Kitchen Fans
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 can increase the level of humidity
in your house. High humidity can damage building
materials. Worse, high humidity can cause mold
growth and mold may harm your family's health.
Common Fan And Exhaust Systems
The two most common types of fans are impeller fans and
Impeller fans move air with blades similar to airplane
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.
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
How Good Is The Fan I Have Now?
CMHC's research shows that many houses have exhaust fans
- are too noisy
- move very little air
- are not energy efficient
- may cause backdrafting of combustion appliances
- use high-wattage lighting
Are There Better Fans?
Yes. There's a new generation of effective, quiet,
energy-efficient exhaust fans and controls.
How Do I Choose the Best System?
First, choose the quietest, most energy-efficient fan in
the size range required. Most fan labels have Home Ventilation
Institute ratings so you can compare noise and energy
efficiency. 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.
Second, select low-resistance (smooth) exhaust ducting.
Seal the joints and insulate sections that run through
Third, place the exhaust hood where it will not cause
moisture damage on exterior surfaces.
Fourth, if you have heating appliances with chimneys, make
sure that fans won't cause the appliances to backdraft.
Fifth, 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
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. Place the
open end of a large, plastic
garbage bag over the exhaust hood. Have someone turn on
the fan. The bag should inflate within seconds.
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. Use a delayed fan
shut-off to keep the fan running for 15 minutes after you
leave the room.
Fans create static electricity which attracts dirt like a
magnet to the fan and 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.
Kitchen Range Hoods
A kitchen range hood must move more air than a bathroom
fan about 50 to 140 L/s (100 to 300 cfm). As a result, they
are noisier, with the lowest rating about 4.5 sones.
The most useful units have a low noise rating, an
energy-efficient fan, fluorescent lights, sound insulation,
anti-vibration mounts and duct connections. For heavy duty
use, select non-corrosive materials such as aluminum or
stainless steel. High quality hoods may have heat sensors and
a safety shut-off.
Kitchen exhaust systems should discharge outdoors.
Recirculating range hoods rely on filters to capture some
odours and grease. The filters are generally made of carbon
which must be replaced frequently to be effective. Grease will
coat carbon, making it ineffective. With recirculating fans,
cooking moisture and odours will usually remain in the
Range Hood Shape
Range hoods are most effective when they extend out over
the stove surface and are close to the stove top. Island units
are less effective than wall units.
Range hoods usually have washable, aluminum-mesh grease
filters. Better quality filters have a smaller diameter mesh
over a larger surface area and can be cleaned in the
There is always the possibility of a grease fire with a
kitchen range hood exhaust. Smooth metal ducting, preferably
galvanized steel, is safer in a fire than lighter
Install fans and exhaust systems so they make the least
possible noise, vibrate as little as possible and leak as
little air as possible.
Anti-vibration pads or foam tape can isolate the fan
housing from wood joists and drywall.You can wrap fan housings
and some duct sections in rubber or vinyl noise barrier
Install exhaust systems according to the building code and
manufacturer's recommendations. Straight, short duct runs,
with few turns, will result in the highest fan flow.
For bathroom fans, use duct with a diameter of at least 100
mm (4 in). For long runs, use larger, 150-mm diameter (6-in.)
to improve air flow. It is usually best to avoid fans with
75-mm (3 in.) exhaust ports and ducts.
Seal all duct joints and connections with aluminum duct
tape or duct mastic (available at contractors supply shops)
to prevent air, moisture and noise leakage. Standard cloth
duct tapes tend to dry out and fall off.
Seal and then insulate all ductwork running through
unheated areas to avoid moisture problems. The best practice is
to slant horizontal runs of duct down toward the exterior
outlet to drain any condensation outside.
Exhaust air should not be released into the attic, into a
wall or ceiling cavity, crawl space, basement or in the roof
soffit. These locations can promote condensation damage and
Weather Hoods, Grills And Backdraft Dampers
Even when fans are off, stack effects and wind loads may
cause outside air to enter or inside air to exhaust through
fan ducting. Fans are equipped with backdraft flaps, usually
in the fan box exhaust port. Check the flaps from time to time
to make sure they are clean and working. The exterior exhaust
flap or louvres should be clean and in good repair to maintain
unobstructed airflow and reduce air infiltration. Most exhaust
ducts are fitted with a single flap exhaust hood or triple
louvre aluminum or plastic exhaust grill. Use weather hoods
that lie flat on the wall in driveways and other places where
hood-type units could be damaged.
Plastic hoods break down over time and need to be replaced.
Clean exhaust hoods of lint and nesting materials seasonally
to ensure that the flap or louvres are not blocked or stuck
Some older bathrooms have static exhausts which look like
upside down funnels on the ceiling. If these exhausts are
hooked into the furnace chimney, disconnect them from the
chimney, seal the hole in the chimney with hydraulic
(expanding) cement, and install a new powered exhaust. If
these static exhausts go directly outside, they can still be
used, but a good fan will be more energy efficient and less
High Capacity Systems
High capacity, industrial or oversized exhaust fans, and
range-top barbecue fans can cause chimney
backdrafting. Backdrafting occurs when air is drawn down
the chimneys, bringing dangerous combustion exhaust gases into
the house. Avoid backdrafting by selecting sealed combustion
heating appliances. If you have appliances with chimneys in
your house, and you wish to install high capacity exhaust
fans, you will need a matching supply air fan to balance house
Many ventilation contractors or salespeople are unaware of
the effects of large exhaust fans on other house appliances.
Make sure that your system is properly installed with supply
air. At the very least, make sure that you have smoke alarms
and carbon monoxide detectors to warn you if you have severe
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