Homer Glen Inspection Blog

Bathroom vent fans

Bathroom vent fans are an often overlooked appliance. The main purpose of the vent fan is to remove the moisture that is created by bathing and showering. Odors are also removed, but this is not as important as the removal of the moisture. Most codes call for some type of venting in a bathroom, whether it be a window or a bathroom fan. If a window is present then a fan does not have to be installed, but I recommend to all my clients to have a vent fan installed for those days that the window can not be used, and for additional venting. Venting this moisture is very important, if not vented, it can permeate the walls and ceilings and cause damage in those unseen areas, it can cause yellow spots and streaking on ceilings and walls, and cause mold and mildew.

The amount of recommended ventilation is 8 air exchanges per hour. Well, how do you know which fan will give you 8 air exchanges? First, most bathroom vent fans are sold with a CFM rating, this is how much air the fan can move in Cubic Feet per Minute. To determine how many CFM you need, you must determine the volume of the bathroom. You will need to have 3 simple mesurements, height, width and length; multiply them, then divide by a constant, which is 7.5 or CFM=Volume/7.5. This will give you the minimum CFM fan that you need.

A bathroom that is 5 feet wide by 10 feet long by 8 feet high needs a fan that is rated at 53 CFM. 5x10x8=400, 400/7.5=53.33 or 53.
This is the minimum CFM that you need.

There is also a sones rating on tha fan. This is the amount of noise the fan creates. The lower the number the less noise the fan creates. This is a personal decision based on how much noise bothers you, choose the fan based on CFM first, then get the lowest sones rating possible in that CFM rating. Do not reduce the CFM rating to get a quieter fan, you will just be reducing the effectiveness of the fan and will not properly vent the bathroom.

Submitted by MikeMerino on Fri, 08/07/2009 - 16:12.
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