How to Calculate Bathroom Ventilation Size

The right size of fan will provide proper ventilation and prevent mold and mildew growth.

Ventilating your home is essential to prevent moisture buildup. Excess moisture can cause mold and mildew to grow in your home, which can be serious health hazards. One of the moistest places in your home is your bathroom. Moisture from sinks, showers and even the toilet can linger in the bathroom for long periods of time unless removed via a fan ventilation system. How can you be sure your fan is sufficient to handle the moisture in your bathroom?

Things You'll Need

• Tape measure
• Calculator

Instructions

Calculate the size of your bathroom

1. Calculate the size of your bathroom in cubic feet. Using a tape measure, measure the length, width and height of the room. Multiply the three numbers together. Suppose the room were 8 feet long, 6 feet wide and 10 feet high. Your bathroom would be 480 cubic feet.

2. Divide the number of cubic feet by 60. Sixty represents the number of minutes in an hour. If your bathroom were 480 cubic feet, you would get a result of 8.

3. Multiply by eight the number you get in step 2. Eight represents the number of air changes that is required per hour to ensure proper ventilation. That number will provide you the minimum cubic feet per minute (cfm) that you need to be drawing out of your bathroom with a fan. So, for our example, we would need a fan that can vent at least 64 cfm.

References

• R.E Williams Contractor Incorporated: Panasonic Bathroom Exhaust Fans