I need a Revit add-in that can scan every Duct and Fitting in an open model, push the geometry and flow data into a lightweight CSV lookup, and return results fast enough to generate an on-screen report almost instantly. The core task is to calculate pressure drop throughout the ductwork and then write an engineering summary that highlights the calculated pressure-drop values and offers actionable recommendations for improvements. Key points you should know before diving in: • The tool must hook directly into the Revit API so users can launch it from the ribbon without exporting anything manually. • It should collect size, length, velocity, flow, and material properties for each duct and fitting, run the pressure-drop formulas, then query the CSV database for any additional coefficients you need. • Once the calculations finish, the add-in should output a clear, well-formatted engineering report (PDF and TXT) that lists every segment’s pressure drop, pinpoints critical losses, and proposes optimisation tweaks such as resizing or layout changes. Deliverables 1. Compiled Revit add-in (.addin + DLL). 2. Source code with comments. 3. Sample CSV file structure and any scripts used to generate or update it. 4. One-click report template that prints to PDF/TXT. 5. Short user guide and a quick video capture showing the solver processing a sample project in seconds. Acceptance Criteria • All ducts and fittings in the active view are processed with no crashes. • End-to-end run time on a 300-element test file stays below 5 seconds on a typical workstation. • Report shows identical pressure-drop totals to a manual spreadsheet check (±1%). • Recommendations section populates whenever pressure loss exceeds user-set thresholds. If you have solid Revit API experience, especially in C# or Python for Revit, and can demonstrate similar automation work, I’d love to review your approach and timeline.