Are you designing primarily in or SI units (metric) ?
One of the most powerful features for Excel users is the database’s export capability. The software can generate CSV or XML outputs for use in Excel, Revit, or other analysis tools. You can copy K‑values into your duct‑sizing worksheet or export files directly for BIM and CFD tools.
Not all Excel files are created equal. A professional-grade database should include the following components:
The ASHRAE Duct Fitting Database (DFDB) provides a standardized method for calculating pressure losses in HVAC systems. While the primary software is a cloud-based or mobile application, it allows users to export results to for comprehensive External Static Pressure (ESP) analysis. 1. Report Overview ashrae duct fitting database excel
The Excel workbook created by Thomas G. Lester, PE, remains a foundational resource. It includes UDFs that solve for friction factor using the Colebrook Equation, then apply those results to duct diameter, flow, and pressure drop calculations.
Many fittings require conditional calculations based on fitting geometry (e.g., the ratio of
Friction loss occurs due to fluid shear stress against the interior duct walls. It is commonly calculated using the to find the friction factor ( ), which is then applied to the Darcy-Weisbach Equation : Are you designing primarily in or SI units (metric)
: Many engineering firms develop custom Excel templates for External Static Pressure (ESP) calculations .
For every specific fitting—such as an elbow, tee, transition, or hood—ASHRAE establishes a dimensionless loss coefficient, designated as Cocap C sub o . The total local pressure loss ( ) for a fitting is calculated using the formula: Δpj=Co×pvdelta p sub j equals cap C sub o cross p sub v is the velocity pressure of the air, calculated as:
Smooth radius elbows are characterized by the r/D ratio (radius of curvature divided by diameter). A 90° smooth radius elbow with R/D = 1.5 serves as a common baseline in examples; its loss coefficient depends on the Reynolds number and can be found in the database. You can copy K‑values into your duct‑sizing worksheet
Many users want to take the vetted loss coefficients from the DFDB and use them directly within their Excel models. The full DFDB includes features to bridge this gap:
The is an invaluable resource for HVAC design. While the official software is powerful, converting the data into an Excel tool allows engineers to customize their workflow, automate calculations, and streamline their design process. By carefully building a database that references standard ASHRAE fitting data, you can create a reliable, fast, and free tool for precise duct pressure drop calculations.