Many homeowners make the mistake of looking at our QuietCool whole house fan and automatically thinking they need the largest unit for their home. QuietCool whole house fans actually work contrary to this belief, meaning that the largest amount of CFM (cubic feet per minute) is not always the best for every home.
Air Exchanges in a Home
QuietCool aims for 15-22 complete air exchanges in the home every hour (one complete air exchange about every three minutes). To achieve these 15-22 air exchanges, a properly sized home should have two to three times more CFM than the square footage of the home. For example, a 2,000-square foot home should have between 4,000 – 6,000 CFM.
This will ensure 15-22 full air exchanges occur and the system functions as designed. *Air must have enough venting to exit the attic properly. See venting requirements or call our tech support team to ensure proper ventilation.
Homeowners who automatically assume they need the maximum amount of CFM possible run the risk of ruining their system since it is likely the motor will fail due to inadequate venting in the attic causing the air in the attic to have no escape route.
This means the air is going to take the path of least resistance which would be to travel down the cracks in the home’s walls, right back into the living space. This results in an inefficient system (before the motor burns out) moving the same air over and over, but not actually flushing the home of the stale air.
QuietCool Whole House Fan Sizing Steps
Fortunately, it is easy to avoid this issue. To ensure your QuietCool whole house fan runs exactly as it is intended, follow these simple sizing steps:
• If you know the square footage of your entire home you can use our system builder to determine what system would give you the greatest results.
• Multiply the square footage by two if it is located in a cool/coastal climate. If the home is located in a hot/desert climate, multiply the square footage by three. This gives you the ideal amount of CFM for the home.
*If the home has ceilings larger than the standard 8-9 feet, size closer to three times the square footage due to an increased volume of air inside the home.
• Check attic ventilation to make sure the air has an escape route to the outside.
• The attic should have one square foot of net-free venting for every 750 CFM the system is bringing in.
*Example: Trident 1.5 pulls in 1,500 CFM. 1,500/750 = 2 square feet of net-free venting needed
to properly ventilate the Trident Pro 1.5.