The DFDB changed everything. It relies on . It treats every fitting (a turn, a tee, a transition) as a puzzle of physics. When you look at a specific fitting in the database, you aren't just seeing a number; you are seeing:

If you encounter issues during your research or software use:

The ASHRAE Duct Fitting Database (DFDB) Version 6.00.05 is a critical software tool for HVAC engineers. It allows for the precise calculation of dynamic pressure losses across more than 200 fitting types.