Ashrae Duct Fitting Database Version 60005 May 2026
Even with the latest database, engineers make mistakes. Avoid these.
For the uninitiated: the DFDB is the digital home of experimentally derived loss coefficients (C₀, C₁, C₂) for thousands of duct fittings. Instead of guessing, you look up a fitting shape, input geometry, and get dynamic loss coefficients. It powers software like McQuay DuctSizer, Elite HVAC, and many in-house tools.
Version 60005 is the latest release under the ASHRAE Research Project RP-1853, and it’s not just a cleanup—it’s an expansion. ashrae duct fitting database version 60005
ASHRAE releases minor iterations (e.g., 60006, 60007) approximately every 18 months to correct errata. Watching ASHRAE's Research Project RP-1802—which focuses on non-standard duct geometries (oval and flat-oval)—the next major version will likely integrate a machine-learning derived prediction model for custom fittings.
However, for the next 3–5 years, Version 60005 will remain the baseline for LEED energy modeling and code-compliant commercial design. Even with the latest database, engineers make mistakes
Version 60005 differentiates between diverging (splitting flow) and converging (joining flow) tees. Using the same (C) for both can cause 200% error.
The database often provides (C) for Static Pressure loss. If your system design uses Total Pressure, you must apply a conversion factor listed in the Appendix of version 60005. ASHRAE releases minor iterations (e
Case A – Hospital HVAC retrofit
An engineer redesigned a critical care wing using v60005. The old database predicted 0.78 in. w.g. for a complex plenum takeoff. New data: 0.93 in. w.g. Result? They upsized two duct runs early, avoiding a fan replacement later.
Case B – Lab exhaust system
A university used the new oval duct fittings to squeeze a high-velocity system into a shallow ceiling plenum. Without accurate coefficients, they’d have oversized the fan by 20%.
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