| FittingID | Shape | Description | Parameter1 (r/D) | Parameter2 (W/H) | Co_value | |-----------|-------|-------------|------------------|------------------|-----------| | E1-1 | Round | 90° Elbow | 0.5 | - | 0.21 | | E1-1 | Round | 90° Elbow | 1.0 | - | 0.19 | | E2-1 | Rect | 90° Elbow | - | 0.25 | 0.30 |

Purchase the ASHRAE Handbook on CD/DVD or Online Access (cost approx. $200–$300). The digital version often includes CSV or tabulated data for many fittings.

But real fittings require two-dimensional interpolation (e.g., for W/H ratios not in the table). A basic VLOOKUP is insufficient.

Introduction For HVAC engineers, designers, and energy modelers, accurate pressure loss calculations for duct fittings are not just a technicality—they are the backbone of efficient system design. For decades, the ASHRAE Duct Fitting Database (DFDB) has been the gold standard reference for loss coefficients. However, the challenge has always been moving this data from static PDF tables (like ASHRAE Fundamentals Handbook, Chapter 34) into dynamic, usable engineering tools like Microsoft Excel.

Many official ASHRAE Excel files include custom VBA functions like InterpolateCoefficient(FittingID, param1, param2) . Step-by-Step: Connecting Excel to the ASHRAE Database via ODBC (Advanced) If you receive the database as a Microsoft Access file ( .accdb ), you can link it directly into Excel without opening Access.