Characterizing the Thermal Inertia of Building Envelope: Experimental Measurement of the effective heat capacity

The thermal performance of the building envelope strongly impacts the energy efficiency of buildings, and is a key point to save energy and improve thermal comfort. The dynamic thermal properties of envelopes have to be accurately calculated and controlled. The Thermal Mass Parameter is used in some European thermal regulations to characterize the thermal inertia of a building; the TMP is calculated from the effective heat capacity of the envelope. Current methods for computing the effective heat capacity of a building element require its thermo-physical properties. Yet, the materials used in construction are often heterogeneous and their thermo-physical properties are not accurately known. In this paper, we use a new method for experimentally measuring the effective heat capacity of a wall element. The wall element is placed under sinusoidal boundary conditions in a climatic chamber. The measures of the parietal temperatures and fluxes are used as inputs in an analytical model, and the calculation is performed. The wall element can be heterogeneous and has to be symmetrical. The method is applied to the calculation of the effective heat capacity of a multilayer heterogeneous wall.