Duct Sizing Chart | Fabric Duct Calculator

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Airflow

CFM

Tonnage

Min 0 / Max 0 cfn / ± 50;

Prihoda Fabric Duct Sizing Recommendations

Straight Duct



50″

1500

FPM (max)

System with fittings/direction changes



56″

1200

FPM (max)

Sound sensitive application



62″

1000

FPM (max)

Typical inlet static pressures required:

.10-.25" w.c. minimum / sound sensitive

.50" w.c. standard / typical

.75" w.c. high volume / high throw

1" w.c. layout with many fittings

General Recommendations:

Match metal size to fabric inlet for a length of 3x dia if possible
Use 1.5x diameter radius elbows prior to and with fabric systems, laminar / smooth transitions, turning vanes etc
For best aesthetics with no or low airflow use internal rings, track and tensioners, or our Helix system (especially if routing through structural members and the unit will cycle on and off)
Utilize a softstart or VFD w/ 30 second ramp up if possible (if no hold open rings or Helix)
Fabric duct will not allow sound from the unit to reverberate inside it and transmit through the space but the metal leading up to the fabric duct inlet can carry noise to the inlet of the fabric duct and the break out of the noise will be loudest at that point. For sound sensitive applications consider the use of metal attenuators, lining the metal duct or fabric attenuators.

Preliminary Planning

This calculator is intended for preliminary planning only and is generally “safe” sizing. If you need a diameter outside of the recommendation on this page due to space limitations please contact us. Since all Prihoda fabric duct systems are made to order, the final design and specifications should be made only after consultation with a certified Prihoda North America representative or a design specialist on our direct sales team. Our comprehensive AirTailor® design software and planning process can help you determine the best design and exact specifications for your particular project. If you’ve already developed plans and would like to request a detailed quote, you can send us your specifications using the detailed quote request form here.