Analysis of the influence of the position of the reflective layer on the thermal performance of a multi-layer lightweight wall panel

Abstract

The work addresses the combined effect of temperature difference, longwave atmospheric heat exchanges and solar radiation in the thermal demand produced through walls with radiative insulation. It focuses in the all-year-round performance of a prefabricated wall panel based on multi-layer reflective insulation. The study has been carried out with analytical models, which have been compared and validated by means of experimental tests. Based on the results obtained for the Santiago de Chile climate, the authors have identified the influence of the position of the reflective layers under the combined winter and summer conditions. From these results on, the study has been extended to other three representative Chilean climates, in order to identify the alternative that suits best for each case. The inclusion of up to four reflective sheets on the sides of the air chambers significantly increases the thermal resistance of the element in all cases, with specific differences depending on the position where the reflective layer is placed. All this makes it a suitable constructive solution for climates where heat exchanges are driven by temperature differences. It has also been observed a good performance against heat gains by solar irradiation incidence, irrespective of the radiative attributes of the exterior finishing. The multiple reflective layers reduce the sol-air daily cyclic variation caused by radiation, and the panel performs similarly to a highly reflective and low emissive surface. The work shows the potential of the reflective insulation solutions to cater for the combined winter and summer requests under the multiple climatic conditions typical of the Chilean complex and varied geography.