This paper presents an experimental finding on the heat reduction window with the use of a phase change material, PCM. A double glaze window is designed and assembled at a test room. The heat flow through the indoor test room via the double glaze filled with air is investigated. Then the function of the double glaze window with a salt hydrated phase change material is studied at a small chamber. Those test facilities are setup. A heat transmitted through the test room and the small chamber via the window is provided by the halogen lamp in which a simulated solar radiation is measured by a pyranometer. The radiation is ranged from 570 to 750 W/m². The characteristic of heat transfer through the double glaze window filled with air and PCM is compared. The experimental results show that the use of PCM for the heat reduction window could reduce the heat transmitted through the chamber. The decrease of room temperature about 1.5 °C is observed.