The DFDB includes loss coefficient tables for more than 200 round, rectangular, and flat oval duct fittings. The database covers a wide array of fitting categories for supply, exhaust, and common (supply/return) duct functions. The full library features over 240 fittings, including many types that are covered by the free "DFDB Lite" app to provide a representative sample:
The ASHRAE Duct Fitting Database is a comprehensive collection of duct fitting loss coefficients, which are used to calculate the pressure drop in duct systems. The database is a valuable resource for engineers, designers, and contractors who work with heating, ventilation, and air conditioning (HVAC) systems.
: For installation troubleshooting or calculation preferences, users can refer to the ASHRAE FAQ page .
When air flows through a straight piece of ductwork, it experiences friction loss. However, when it encounters a fitting—such as an elbow, tee, transition, or hood—the air changes direction or velocity, creating turbulent eddies. This disruption causes dynamic pressure loss.
You can download Version 60005 directly from the ASHRAE Bookstore or through your licensed DFDB portal. If you use a third-party tool (like Trane Duct Designer or Elite Software ), check with their support team—most major platforms will release a compatibility patch within the next 30 days.