Kentaro MORITA Suguru MORIComputer software for simplifi ed simulation of thermal environment of glassed-in spaces was developed to support planning of those spaces. The software outputs the temperature and the relative humidity of glassed-in spaces after users input the date, the location, the layout of those spaces (dimensions and direction), the specification of surfaces (roof, four walls, and fl oor), the setting of fl oor heating and the condition of natural ventilation.Compared the predicted temperature with the actual measured temperature of a real glassed-in space, it appears that the software is a practical tool for understanding the overall behavior of thermal environment of glassed-in spaces, or for comparing the characteristics of thermal environment of those spaces under different input conditions.