Thermal behavior of a window of a building affects indoor thermal environment, especially affects heating and cooling loads significantly. And heating and cooling loads of a window is a major elemental part of whole of loads. Changes of heat transfer reflects the heat load calculation for moment to moment. The authors used multiple units of the experimental apparatus and collected data in short time intervals by the latest high speed data logger to analyze the measured data theoretically. Temperatures at 6 experimental apparatus were measured. Then, examination using the LESCOM simulation program was conducted. The measurement discovered that the indoor thermal environment was improved substantially. It was also found that figures gained from the measurement agreed well with those calculated from the LESCOM program. Climate change nowadays is saying extraordinary. The authors executed heat-load simulation with weather data of the last decade which is considered prefers to that of standard. As the results, we concluded that the simulation with the last decade is important, since it is able to evaluate standard heat-load according to annual difference.