Convention Applied by the app hvac.duct.schedule-factors
Duct Schedule factors
The estimating knobs the Duct Schedule starts with — seam and waste, the quick-bid fitting factor, the design friction rate and velocity cap the ductulator suggests sizes from, and the terminal allowance the static-path check adds at the end of the critical path.
| When | The app uses |
|---|---|
| seam and waste, on the straight-duct pounds | 15 % |
| fitting factor, when fittings are not counted individually | 40 % |
| design friction rate for size suggestions | 0.08 in w.g. per 100 ft |
| maximum velocity for size suggestions | 1200 fpm |
| terminal allowance (diffuser + flex) added once at the end of the static path | 0.1 in w.g. |
- Source
- trade practice · estimating convention; ASHRAE Fundamentals duct design for the rate and velocity
- Editions checked
- —
- Used by
- Duct Schedule
- Amendments
No state or local amendment to this rule is on file. Not on file means the model code as written — check your jurisdiction.
A working figure the trade uses and the app defaults to. Shops override these most.
None of these is a code figure. They are the numbers a sheet-metal estimator carries: a percentage on the straight pounds for seams, laps and the offcuts that never leave the shop; a percentage that stands in for fittings on a quick bid; the friction rate and velocity ceiling a designer sizes low-pressure supply to, which is what the ductulator suggestions in the size chip use; and the terminal allowance — the static a diffuser and its flex drop take at the end of the longest run — that the Bid Check's static-path row adds once to the critical path's friction loss before comparing it with the unit's external static.
What the app does with it
The Duct Schedule modal shows all five on its Suggestions row and applies them per project; they are saved with the project and restored on every load. Counted fittings replace the fitting factor when you switch the mode. The friction rate does double duty: it sizes the suggestions and it prices the critical path in the Bid Check's static-path row (equivalent feet × rate ÷ 100, plus the terminal allowance).
What it does not do
The suggestions size for friction and velocity only. They do not account for noise criteria or an engineer's schedule, which wins when there is one. The static-path row uses equivalent-length rules of thumb for fittings, not a coefficient-by-coefficient loss calculation, and it is a check on the estimate, not a design.
Cited by section, not reprinted: the code text belongs to its publisher. Company practice is not a rule here — it lives with your pricing.