Bathroom Ventilation
Systems

Besides removing unwanted odors, . bathroom ventilators are also designed to remove excess mosisture to control mold and mildew.

Most bathroom ventilation systems are installed at the time of construction and remodeling.

Being in the heating, ventilation and air conditioning business, I find it puzzling that the person who usually installs a bathroom ventilation system is the electrician.

No offense to electricians, but the ones that I come into contact with at construction projects know very little about the principles of ventilation.

Sure, they know how to wire them, but there is more to it than just attaching wires.

Properly sizing a bathroom vent is a must in order to do the job for which it is intended.

Fans are rated in CFM (cubic feet per minute). The object is to remove a certain amount of cubic feet of air from an area in one minute.

Sizing Example

Bathroom size - 8 feet long x 5 feet wide x 8 feet high.

Multiply these numbers to find the area in cubic feet.

8 x 5 x 8 = 320 cubic feet.

To properly ventilate a bathroom, a vent fan should be able to change all the air in the bathroom 8 times in one hour.

This is called air change per hour (ACH).

Our example bathroom has 320 cubic feet of air.

By multiplying 320 (Cu.Ft.) x 8 (recommended air changes per hour) we now have 2,560 cubic feet of air that has to be changed.

Next, divivde 2,560 by 60 (minutes/hr.) = 43(remember CFM?).

You would now choose a fan that will have a CFM rating that is closest to 43 CFM.

Controlling The Fan

Some bathroom fans have a simple on/off switch and some are wired along with the bathroom light.

The problem with this is it doesn't give the fan enough time time to do it's job if you turn the light off as soon as you leave the bathroom.

There are switches available that allow the fan to shut off automatically 20 minutes after it's turned on.

Proper Vent Piping is a Must

Be sure the fan is vented to the outdoors.

A common mistake that's made is venting the fan directly into the attic.

This causes problems such as mold and water damage to the roof deck.

I don't recommend the use of flexible, plastic duct.

First of all, it has more resistance to airflow than smooth duct.

This can reduce the capacity (CFM rating) of the fan.

It always sags, creating a trap for the mositure that can condense in the line and eventually causing the duct to break.

I've seen this happen more than once.

We use schedule 40 PVC. It's smooth, water-friendly and lasts a long time.

Another alternative is solid aluminum duct (stay away from the flexible if possible).

Don't Buy a Cheap Fan

They are noisy and annoying. Always buy one with the lowest sone rating.

A sone is a measurement of sound. The lower the sone number the quieter the fan,

We use a Panasonic bathroom ventilator because they are quiet and have a high quality, long lasting motor.

Follow all the steps mentioned to keep your bathroom air fresh and the walls dry.

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