Comparative Analysis of Roof Geometries for Rainwater Harvesting using CAD Modeling in Autodesk Inventor

This study proposes a geometric optimization approach for rooftop rainwater harvesting systems using parametric three-dimensional modeling. The study addresses the influence of roof shape on hydraulic efficiency under controlled conditions, holding constant slope, projected area, runoff coefficient, and precipitation parameters. Three common configurations: a gable roof, a mono-pitched roof, and a butterfly roof, are modeled using Autodesk Inventor to compare their potential harvesting volumes. The analysis isolates the geometric effect by applying a uniform runoff coefficient to each model and calculating the theoretical annual volume based on the effective sloped area. The results show that the butterfly roof significantly improves hydraulic performance, with an 18 percent increase over the reference flat model, while the other configurations show equivalent improvements of 6.35 percent. The methodology allows efficiency prediction without the need for physical prototyping and highlights the value of CAD-assisted conceptual design in stormwater harvesting systems. These findings provide a replicable framework for optimizing performance in rural regions with high rainfall and guide future research with CFD simulations and experimental validations.