A new method for measuring thermal resistance of building walls and analyses of influencing factors

Abstract

The thermal resistance of the building wall is one of the most important parameters of thermal performance, it will impact the building energy consumption and indoor thermal comfort directly and greatly. The present methods for thermal resistance measurement of building walls are mainly derived from the heat flow meter method and the hot box method, which require a rigorous measurement environment and tedious measurement steps. In this paper, a new method to measure the thermal resistance of the building walls based on the analytical solution was proposed. Firstly, a board was placed on the interior surface of a wall, and an analytical solution of the heat transfer process in the building wall along with the board was obtained. Then the temperature of the interface between the wall and the board was measured. Finally, the thermal resistance of the wall could be calculated based on the analytical solution and the measured temperature values. The new method was also verified in this research. It was found that no matter the single-layer or the multi-layer walls, the relative errors were all less than 10%. When the thermal resistance of the building wall is low, a board with low thermal conductivity such as fiberboard could be used. When the thermal resistance of the building wall is high, the flat glass is a good choice. The temperature values of the interface at the moments of 70 h and 75 h are suitable to calculate the thermal resistance of the building wall.