Generalized design principle and method for a non-balanced thermal insulation system in building envelope

Abstract

In regions with abundant solar energy, building walls facing different directions absorb very different amounts of solar energy. These differences should be considered in thermal insulation design, unlike the current design standard in China, which does not take directionality into account when calculating the limit value of the heat transfer coefficient of building envelope. To address this short-coming, this article proposes a generalized non-balanced thermal insulation system for the building envelope: walls receiving greater amounts of solar energy should have less insulation, while walls receiving less amounts of solar energy should have more insulation. By analysis of outdoor synthetic temperatures for different orientations, non-balanced heat transfer coefficients are calculated under a constant heat flux condition. Considering the Lhasa region as a case study, the testing of an indoor thermal environment in winter was conducted, and a novel non-balanced thermal insulation system was built. The internal surface temperature of the external walls under two types of heat transfer coefficient limit values and the frequency responses of the two types of thermal insulation wall constructions are analyzed using the wall thermal theoretical method. The results show that this new thermal insulation design can make better use of solar energy, thus reducing conventional heating. This article provides a theoretical reference for the future design of non-balanced thermal insulation systems for building envelope and also provides a theoretical calculation method for the part of building envelope thermal design in the national standard of the People's Republic China (Thermal Design Code for Civil Building-GB50176).