Massive and Lightweight Building Envelope Design for a High Level Summertime Performance

Recent researches have shown that considering the superficial mass [M_s] and the periodic transmittance [Y_mn] of building envelopes is not sufficient in order to realize energy savings and a high level internal comfort in the summer period. For this reason experimental reference values for the parameter of internal areal heat capacity [k₁] were introduced. This parameter describes the actual capacity to accumulate heat on the inner side of a building element and identifies the internal thermal mass. The aim of this study is to understand the interdependencies between the thermal parameters (U, M_s, φ, Fa, Y_mn and k₁) of massive and lightweight external walls with respect to the summer energy performance and, in particular, for the control of the thermal transfer and thermal inertia. The study analyses various external walls, considering both the heat flux into the building and the internal thermal load, in order to provide design proposals for improving thermal performance in summer and obtain a high level summertime comfort.