Standard Residential Friction Loss: 0.1 in. w.g. per 100 ft • Based on ACCA Manual D & ASHRAE Standards
| Dia. | CFM | Velocity | Recommended Use |
|---|---|---|---|
| 4" | 37 CFM | 426 FPM | Bath exhaust |
| 5" | 67 CFM | 492 FPM | Small bedroom |
| 6" | 109 CFM | 553 FPM | Standard bedroom |
| 7" | 163 CFM | 611 FPM | Master bedroom |
| 8" | 232 CFM | 666 FPM | Living branch / trunk |
| 9" | 317 CFM | 718 FPM | Zone trunk |
| 10" | 419 CFM | 768 FPM | 1-Ton main trunk |
| 12" | 678 CFM | 863 FPM | 1.5–2 Ton main trunk |
| 14" | 1019 CFM | 953 FPM | 2.5-Ton trunk (953 FPM) |
| 16" | 1450 CFM | 1039 FPM | 3.5–4 Ton trunk |
| 18" | 1980 CFM | 1120 FPM | 5-Ton trunk / light comm. |
| 20" | 2615 CFM | 1199 FPM | Commercial trunk |
| Size (W×H) | CFM | Equiv. | Velocity |
|---|---|---|---|
| 8×6" | 200 CFM | 7.6" | 599 FPM |
| 10×6" | 264 CFM | 8.4" | 634 FPM |
| 12×6" | 330 CFM | 9.1" | 661 FPM |
| 10×8" | 393 CFM | 9.8" | 708 FPM |
| 12×8" | 496 CFM | 10.7" | 743 FPM |
| 14×8" | 600 CFM | 11.5" | 772 FPM |
| 16×8" | 706 CFM | 12.2" | 795 FPM |
| 18×8" | 814 CFM | 12.9" | 814 FPM |
| 20×8" | 922 CFM | 13.5" | 830 FPM |
| 12×10" | 673 CFM | 12.0" | 807 FPM |
| 14×10" | 819 CFM | 12.9" | 843 FPM |
| 16×10" | 969 CFM | 13.7" | 872 FPM |
| 18×10" | 1120 CFM | 14.5" | 896 FPM |
| 20×10" | 1274 CFM | 15.2" | 917 FPM |
| Dia. | Stretched | Installed | Velocity |
|---|---|---|---|
| 4" Flex | 33 CFM | 30 CFM | 344 FPM |
| 5" Flex | 59 CFM | 54 CFM | 396 FPM |
| 6" Flex | 96 CFM | 88 CFM | 448 FPM |
| 7" Flex | 144 CFM | 132 CFM | 494 FPM |
| 8" Flex | 204 CFM | 188 CFM | 539 FPM |
| 9" Flex | 279 CFM | 256 CFM | 579 FPM |
| 10" Flex | 369 CFM | 338 CFM | 620 FPM |
| 12" Flex | 597 CFM | 548 CFM | 698 FPM |
| 14" Flex | 897 CFM | 823 CFM | 770* FPM |
| 16" Flex | 1276 CFM | 1172 CFM | 839* FPM |
| System Size | Min. Round | Min. Rectangular | Design Velocity |
|---|---|---|---|
| 1.0 Ton (400 CFM) | 12" | 14×8" / 12×10" | 509 FPM |
| 2.0 Ton (800 CFM) | 14"–16" | 20×10" / 24×8" | 573 FPM |
| 3.0 Ton (1,200 CFM) | 18" | 26×10" / 22×12" | 611 FPM |
| 4.0 Ton (1,600 CFM) | 20" | 30×10" / 26×12" | 660 FPM |
| 5.0 Ton (2,000 CFM) | 22"–24" | 34×10" / 30×12" | 679 FPM |