Ideal thermal physical properties of building wall in an active room

Abstract

Optimizing the thermal physical properties of building envelope can decrease the energy consumption in active rooms. In this paper, a method of determining the ideal thermal mass characteristics of an active room wall has been developed, which can derive the optimal thermal physical properties of building walls by minimizing additional energy consumption. For demonstrating purpose, some illustrating examples are presented. The results show that: (a) the ideal specific heat distribution with temperature of the thermal mass for an active room approaches the δ function, which has the characteristic similar to that of phase change materials; (b) the thermal conductivity of internal wall has little effect on the optimized heat (cooling) load and the characteristic temperature when it is higher than 0.5 W m⁻¹ K⁻¹ for the simulated room in Beijing. The additional heating and cooling energy consumption approaches zero when the excessive enthalpy of internal thermal mass is higher than 30 MJm⁻³ and 300 MJm⁻³ for Beijing in winter and summer, respectively, and the corresponding characteristic temperatures are 18℃ and 26.3℃ and (c) for practical use, the excessive enthalpy should be added in the internal thermal mass targeting both winter and summer performance in order to decrease the additional energy consumption.