Bathroom Ventilation

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Bathroom Ventilation

Most bathrooms have some sort of ventilation system. Many people overlook the importance of proper ventilation in the bathroom. Your exhaust fan removes excess moisture and nasty odors, keeping mold and mildew from becoming a problem and keeping your air healthy. To keep it running its best check out these tips:

Clean your exhaust fan twice a year. Most exhaust fans have covers that simply pull off or are held on by just a screw or two. Remove the cover and clean the vent slots. Also, check the fan for dust build-up. Either brush or vacuum off any accumulation that may have attached itself to the fan. You’ll be surprised how much dust will be in your fan. Just a light covering of dust on the fan can reduce the fan’s performance by 20-40%.

Keep the door or window open a bit. If the bathroom is sealed off tight while the fan is on, then the fan has no place to draw air from, thus it can’t put the moist air outside. No air flow into the bathroom will take away 90% of the fan’s power to exchange in the bathroom.

After a shower, let the fan run another 5 minutes or longer.

Remember that the primary function of a ventilation fan is to get rid of moisture, so it's crucial that the unit be vented all the way to the outside of the house. Venting a fan into the attic simply takes the moisture from the room and puts it up into the attic, where it can do just as much long-term damage to your house - it's also a violation of the building codes.

Options

Fans are available as a fan only; a fan/light, which combines an incandescent or fluorescent ceiling light with the fan; a fan/heat, which combines the fan with or one or two heat bulbs; and a fan/heat/light, which combines all three. You'll also have a number of options for how to control the unit, ranging from a single switch that turns on the fan and light at the same time to multiple switches that control each function separately. You can use a timer to ensure that the fan shuts off after a certain number of minutes.

Fan Placement

The aim of locating the fan is to get the air to flow across the room, without taking a shortcut and leaving an area unventilated. This means if there is a window; the air shouldn’t come in the window then straight to the fan without passing across the room first. It is really a matter of common sense. Put the intake as close to the problem as possible, which normally means over the top of the shower stall.

The Best Fan for Your Situation

There are really four things you need to be concerned about in the selection and installation of a bathroom ventilation fan - air movement capacity, noise level, ducting and optional accessories. Each plays an important role in the fan's proper operation.

Air Movement Capacity

Fan exhaust capacity is rated in liters 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. 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 odor.

Building Code Requirements (Summarized)

Buildings shall have a means of collecting or otherwise removing: cooking fumes and odors; steam from laundering, utensil washing, bathing and showering; odors from sanitary and waste storage spaces; poisonous or flammable fumes & gases…”
where fans are used to remove moisture and other contaminants from kitchens, bathrooms and laundries in housing, the exhaust air must be ducted to the outside, whether or not the fan is a requirement of the Building Code.
For internal rooms without natural ventilation, mechanical ventilation (extraction fans) must be installed to extract the air at given rates. Residential kitchens; 50 l/s, bathrooms and toilets: 25l/s, laundries 20l/s.

These are minimum Building Code requirements. Generally, this would not fulfill your expectations of moisture and odor removal. We recommend that you consider the following industry recommendations when choosing your fan.

The ventilation industry has a “Recommended Air-Changes per Hour” solution. i.e. An air flow rate sufficient to remove/replace the total volume of air in a given room a specified number of times each hour. Obviously fans will not necessarily be left running for an hour – a fact which is taken into consideration in the formula.

Industry Recommendations

Recommendations For Air Changes Per Hour – Guide only individual requirements may vary

Application Description	Air Changes Per Hour
Bathrooms	5-8
Kitchens (Private)	10-15
Laundries	10-30
Toilets (Domestic)	2-3

Working out the right fan for the job:

1. Calculate the room volume in meters (LxWxH)

2. Multiply the room volume by the recommended air changes per hour for that room.

3. The sum is the total air changes required in cubic meters per hour

Select a fan with the closest performance to this figure.

Noise Levels

In order to be effective, a bathroom fan needs to be used and that usually won't happen if it's too noisy. For that reason, the second consideration in the selection of your fan should be the amount of noise it makes while in operation.

In addition to the l/s rating discussed above, ventilation fans also carry a noise rating, listed in dBA. Several things affect how loud or quite a fan is - its air-moving capacity, the type of fan blade assembly being used, how much insulation is placed in the fan housing, and where the fan is located. As you probably would expect, the quieter the fan is, the more you can expect to pay for it. Fans are a long-term investment, and the quieter unit is well worth the extra initial cost.

Installation and Ducting

Most fans are designed for direct ceiling mounting within the bathroom itself. There are also fans designed to mount in the wall, and fans, which mount in a remote location - up in the attic, for example -- to further cut down on noise.
There are two major types of extractor fans – axial and centrifugal. The difference between both types is power and method of installation.

Axial Flow Fans

Axial flow fans utilize a propeller type blade to move the air in line with the axis of the motor. They are very efficient at moving large volumes of air through walls or windows into free air but have a limited application where ducting is introduced.

Centrifugal Extractor Fans

Centrifugal fans incorporate drum type blades and move the air at 90 degrees to the axis of the drive motor. They do not achieve the same air volumes for a given power output as axial fans but generate much higher pressures which make them ideal for ducted installations

Installation Do's and Don'ts

Fans, when connected to ducting, operate best when the ducting is installed so that any restrictions to the flow of air are minimized. Fans can be mounted anywhere along the dust system but care should be taken as not to restrict the airflow.

Maximize the distance between the fan and inlet/outlet grilles to reduce noise at grilles.
Don’t leave ducting slack, extend flexible ducting fully, cut to correct length, remove bends where possible. Support the duct so that is its straight.

Ducting should be the same size or larger than the fan spigot to optimize airflow. Don’t squeeze ducting into the fan spigot as this restricts the airflow.

There you have it, a complete guide to Bathroom Ventilation to tackle the job from an expert in the industry.

Article credits:

AIRFLOW ENGINEERING (SI) LTD
30c Carlyle Street, Christchurch, New Zealand
Ph: 64-3-365-6278 Fax: 64-3-365-6272