Evaluation of heat flux reduction provided by the use of radiant barriers in clay tile roofs

In Brazilian towns and cities the greatest thermal gain occurs through the roof of single-storey buildings. In this regard, the use of thermal radiation barriers has the function of minimizing the heat flux through the roof. Even though the use of this type of thermal insulation has increased in recent years; there are still no technical standards which address the subject. Thus, many products have become available on the market which have the appearance of a radiant barrier, but without low emissivity, and not functioning properly as thermal insulation. The objective of this study is to analyze the efficiency of some types of radiant barriers found on the civil construction market, as well as to analyze the efficiency of sheets made from the joining together of a solid urban waste, long-live carton packaging, in loco and in the laboratory. The in loco measurements were carried out in a roof of a residence in the city of Florianópolis, where the heat flux, surface temperatures of the tiles and the ceiling, and the internal and external temperatures, were monitored. The laboratory experiments were carried out with an apparatus which simulates the thermal resistances of a real roof. The results allowed the verification of which is the best type of radiant barrier, that is, which achieves the greatest reduction in heat flux through the roof. This study also allowed a comparison between the in loco and laboratory results.