SuperiorHeatingAndAir.com

Is there anything wrong with using 4 inch diameter supply air ducts for heating & air conditioning a home?

The air would be supplied at low velocity of 500 cfm. Oops! I need to correct details. Sorry! The supply air will be moving through the ducts at an approximate velocity of 500 feet per minute. Each duct will supply approximately 50 cfm. Oops! I need to correct details. Sorry! The supply air will be moving through the ducts at an approximate velocity of 500 feet per minute. Each duct will supply approximately 50 cfm.

Public Comments

1. 500 cfm through a 4 inch duct will be very noisy.
2. I agree with Duck; I believe it is going to sound like a tornado. Ducting is usually sized depending on the distance from the blower. The duct reduces in size, the farther from the source (sort of like putting your thumb over a water hose) to increase the velocity. You may be at 500 cfm at the source, but it is less the farther you get so the duct gets smaller. I can't imagine that the entire system would be ducted with 4". There used to be systems called "spacepaks" that had these crazy little ducts, but they didnt' work particularly well