Recently, the increase in production, consumption causes the shortage of the natural resources and the increase in waste disposal. In order to build up a sustainable society, the input and the output of the natural system should be reduced by the recirculation of materials and energy. We have tried to develop high performance building materials by solidification technology at low temperature. The starting materials were the inorganic wastes or soil. These solidified inorganic waste and solidifying soil have good mechanical strength for paving tile. Solidifying soil called as Tataki works has good performance of mitigating urban heat islands. Numerical simulation method based on heat transfer model was studied to estimate performance of mitigating urban heat islands of solidifying soil. Numerical model was calculated by the surface temperature changes in the outside with air temperature changes. Simulation result was compared with experimental measurement.