Abstract
In order to evaluate thermal environment improvement on the Fukuoka City Hall Square, a field demonstration experiment was carried out using water retentive materials. The materials applied were natural grass sheets and water-retainable artificial grass sheets. These materials were installed temporary on the square made from white artificial stones, and the thermal properties were observed in summer season. Thermal radiation on the human body was improved on each material in the daytime, but the atmospheric heating by sensitive heat in the daytime was increased on the artificial grass, because of the surface temperature rising.