Understanding Air Flow Efficiency Ratings on Whole House Fans

Among the most important factors that you should consider when you are choosing a whole house fan is energy consumption. The higher your rating for ‘Air Flow Efficiency’ (CFM/Watts) the better.

The way whole house fans are rated is based on how much air they can move. This is calculated in cubic feet of air per minute; also known as CFM. The CFM rating of a whole house fan should be 1.5 to 3 times the home’s square footage to be effective. For instance, for a home that is 1,500 square feet, the whole house fan should have the ability to move 3000 to 6000 CFM of airflow, depending on whether the goal is for “efficient cooling” or to have a “breeze effect”.

New Ventilation Requirements
Due to new ventilation requirements, fans that are designated for ventilating the entire home will have more hours of operation as opposed to kitchen or bathroom fans where they are operated temporarily for removing local odors and humidity. Operable windows or infiltration was relied upon by the earlier ventilation practices as the main source of ventilation air.

Dwelling units and homes under these new requirements will use up substantially more energy on fan usage, therefore, enhanced fan efficiency for those fans is more cost-efficient and required through the 2012 International Energy Conservation Code (IECC). New requirements for fan efficacy are explained in this code note as well as how to decide which fans are under these requirements.

How Energy Efficiency is Rated
Whole house fans, through the California Energy Commission Appliance Efficiency Database are rated by brand name, manufacturer name, fan type, model number, CFM air flow as well as the air flow efficiency. How much air flow there is per watt is what the energy efficiency is based on and the greater the ratio is for the CFM-watt, the more the appliance is energy efficient.

Economy or older style kitchen, bathroom or whole house exhaust fans will probably not meet the requirements for fan efficacy; however, they can still be used as long as they are not being used for any part of the whole house ventilation system. Because of this, the efficacy of these fans will not be enforced indirectly in the market due to minimum efficacy manufacturing requirements.

You can browse the California Appliance Energy Efficiency Database to see data and information from testing which requires manufacturers to certify the performance and energy use of their appliances. By conducting a simple search, you will be able to locate the whole house fans tested CFM ratings. QC Manufacturing, Inc. provides the true CFM rating for all their fans, which means once you install your QuietCool fan, you get the real CFM that is listed in their specifications.

Still have questions about air flow efficiency ratings on whole house fans? Give us a call at 1.888.229.5757 or chat with us online for free expert advice.