Duct and Termination Reference
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Use a practical duct reference for length, elbows, filters, grilles, dampers, wall or roof terminations, sound concerns, and the information needed before fan selection.
A fan request is incomplete when it only names CFM or duct diameter. The installed route, restrictions, termination, sound target, control path, and service access determine what needs to be checked next.
Keep this reference beside the ventilation CFM calculator, bathroom exhaust fan sizing calculator, and duct fan static pressure estimator. It organizes the path; it does not replace a project-specific duct calculation or fan curve.
Record the actual termination and access conditions instead of assuming that a nominal duct size represents delivered airflow.
This resource supports early planning; confirm certification, code requirements, and final equipment selection against current project and model documents.
Reference table
| Path item | Record | Why it matters | Next review |
|---|---|---|---|
| Straight duct | Size, material, route length, direction changes | Sets the baseline resistance and service path | Static pressure and fan curve |
| Elbows and transitions | Count, angle, size changes, flexible sections | Fittings can add resistance and noise | Duct fan selection |
| Filters and grilles | Type, face size, clean access, replacement path | Adds pressure and maintenance requirements | Cabinet or filtered fan review |
| Dampers and controls | Backdraft, balancing, motorized, timer, humidity or speed control | Changes airflow behavior and wiring scope | Controls and model documents |
| Wall termination | Wall cap, shutter, opening size, weather exposure | Outdoor restriction and discharge condition affect the route | Wall exhaust or inline fan review |
| Roof termination | Roof cap, curb, flashing, service access | Discharge and maintenance conditions need coordination | Project installation review |
| Sound path | Room sensitivity, mounting surface, duct lining, target | Listed sound values do not describe every installed path | Sone and model data review |
Technical FAQs
Is duct diameter enough to select a fan?
No. Length, fittings, filters, grilles, dampers, termination, target CFM, sound, and access can change the equipment path.
Does this page calculate static pressure?
No. It helps collect the route facts. Use the estimator for an early pressure intake and confirm the installed path with project-specific calculations and model fan curves.
What should I photograph?
Photograph the fan location, duct connection, elbows or transitions, filters, grille or cap, electrical access, controls, and the service side.