Using the correct, up-to-date loss coefficients isn't just about efficiency; it's about contractual accuracy. If you are specifying fan static pressure, using an outdated database (pre-60005) might under-spec your fan by 5-10%.
Version 60005 introduced a "caveat" flag for fittings where the (C) factor is valid only within specific velocity ranges (e.g., 800–2,500 FPM). Ignoring these caveats is a common design error.
: Includes access to the Duct Fitting Database Lite app for iOS, allowing for field-based pressure loss calculations in both I-P and SI units.
: The interface allows users to input flow rates and fitting dimensions to obtain instantaneous loss coefficient data and pressure loss results. Cloud-Based Access
won’t win design awards, but it will save energy, reduce noise complaints, and make your pressure drop calcs actually match reality. If you design air systems, download it. If you teach HVAC, update your slides. If you’re still using generic loss coefficients from 1995… we need to talk. ashrae duct fitting database version 60005
During the design phase of an air distribution system, engineers must calculate the total pressure drop across the longest or most restrictive duct run (the critical path). This calculation determines the static pressure requirement for the supply, return, or exhaust fans.
Includes supply, exhaust, and common duct functions based on the ASHRAE Handbook—Fundamentals .
Includes loss coefficient tables for over 200 round, rectangular, and flat oval fittings .
To appreciate the utility of the DFDB, it helps to look at the fundamental equations driving the software. The dynamic pressure loss ( ) of a fitting is calculated using the following formula: Using the correct, up-to-date loss coefficients isn't just
), maximum velocities are typically governed by noise and energy efficiency goals. Subscription and Access
: Includes pictorial outlines for over 200 fittings across supply, exhaust, and common duct functions.
ASHRAE TC 5.2 (Duct Design) revisited the empirical data for common fittings, particularly and rounded rectangular elbows . Some coefficients changed by as much as 15% compared to previous versions, meaning designs based on older databases may be significantly under- or over-estimating pressure drop.
Users can save fittings into project files that are easily stored, navigated, and transferred between workstations. Ignoring these caveats is a common design error
For engineers looking to ensure their designs are precise in 2026, subscribing to the latest ASHRAE Duct Fitting Database is a necessary step.
: Fittings can be grouped and saved into individual project files, which are small enough for easy transfer and navigation.
Stay tuned for our follow-up post: “How to Convert DFDB 60005 Data into Excel Pressure Drop Matrices.”