In this paper, an energy analysis model is set up in order to clarify the effect of insulation materials on the thermal performance and the energy consumption of building envelope. Three types of insulation materials commonly used in Germany including mineral fiber, polyurethane and vacuum insulation panel are chosen as the case study. The calculational results show that the energy consumption increases with the increasing of the insulation thickness while the heat losses decrease. So there exists an optimum thickness of the insulation to get the lowest total energy consumption. The ascending order of the total energy consumption of the three materials is mineral fiber, polyurethane and vacuum insulation panel. While their optimum insulation thicknesses show an reverse order with the increasing of heat transfer coefficients of the base envelope. Moreover, the energy payback time of each material is analyzed at the optimum thickness, which is greatly affected by the heat transfer coefficient of the base envelope. The longest pay back time is up to 21 years for the vacuum insulation panel if the base envelope heat transfer coefficient is as small as 0.2W/m².K.