A Model of Effective Thermal Conductivity for Planting Soil of Green Roof

For insulation, green roof has been widely applied and researched in recent years. The effective thermal conductivity (ETC) of planting soil of green roof plays an important role to insulation. The ETC of six kinds of compound planting soil, usually used in green roof，were measured with different water content. The results show that the ETC of compound planting soils has linear relationship with weight humidity. A sensible, albeit simplified mathematical model, with weight humidity and dry apparent density as variables, was established for the dynamic ETC of compound planting soil. To verify model accuracy, the calculation data of ETC of compound planting soil, which under natural climatic conditions for 2 years, were compared with experimental data, and the results indicate that the model have high accuracy in a wide range of weight humidity. In additional, the ETC proper range of compound planting soil was derived.