Hello,
Recommended velocities, FPM
Residence:
Main duct: 700-900
Branch duct: 600
Schools, Theaters, Public Bldgs:
Main duct: 1000-1300
Branch duct: 600-900
Industrial bldgs:
Main duct: 1200-1800
Obviously the duct velocities for the residence will give
the least noisy duct. You have to balance the cost against
the lack of noise.
Branch duct: 800-1000