The study aims to demonstrate a process for sizing the windows of a passive solar house case study that involves a multi-decision problem. The initial design was created in an earlier stage, during which, decisions on broader issues such as building orientation, form design, and the appropriate spatial organization of the building were made. It applies a variety of methods to generate and evaluate design alternatives such as rules of thumb and LCR method for passive heating; earth cooling and cross ventilation rules of thumb for passive cooling; and daylighting factor for daylighting. At the end, the study makes preliminary performance estimates between two alternatives to choose a final solution.