Envelope wall/roof thermal performance parameters for non air-conditioned buildings

Many parameters have been used to evaluate the thermal performance of envelope wall/roofs, most of them for air-conditioned buildings. In this paper, the interest is focused on parameters to assess the thermal performance of envelope wall/roofs for non air-conditioned buildings. Five groups of parameters, some previously used and some newly proposed, have been analyzed. To test the evaluation parameters, numerical simulations of the periodic heat transfer through five different roof configurations have been carried out. This research shows the suitability of the energy transferred through the wall/roof during a day, the decrement factor, the discomfort degree hours, and the hot (or cold) thermal performance index to be used for thermal evaluation of wall/roofs in non air-conditioned buildings. The sensitivity of these parameters with climatic conditions and with the outdoor surface solar absorptance is analyzed. Additionally, it has been shown that the steady-state thermal transmittance, the thermal admittance modulus, the periodic thermal transmittance modulus, and the surface decrement factor, calculated with surface temperatures, are not suitable parameters to evaluate wall/roofs in non air-conditioned buildings.

► Parameters to evaluate thermal performance of envelope wall/roof for non AC buildings. ► DF calculated with solar-air and indoor air temperatures is adequate for nACB. ► Time lag, discomfort degree hours, TPI, heat transfer are adequate for nACB. ► TPI, discomfort degree hours, and heat transfer are sensitive to climatic conditions. ► Decrement factor (DF) calculated with surface temperatures is not adequate for nACB.