Thermal performace of glasses in building construction: study in test-cells / Desempenho termico de vidros utilizados na construção civil : estudo em celulas-teste

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Thermal performance of buildings depends on several factors, such as implantation, orientation, materials and building components, which should be appropriately defined for different climate conditions. The building acts as a controller of the climatic variables, through the building envelope (walls, floor, roof and openings) and the nearby elements. Building design must provide indoor comfort and energy efficiency. Glazing easily allows the penetration of solar radiation into buildings, due to its transparency to solar radiation. So glasses must be carefully considered in building design, having in mind their potential for internal heating. In this work studies about the behavior of transparent façades, in real conditions, were carried out through measurements in six test-cells with dimensions 2,00 x 2,50m. Fourteen types of glasses were selected: five float glasses, four reflective glasses produced by pyrolitic process, three reflective ones obtained by vacuum metal deposition and two laminated glasses. Their spectral behavior was known from previous spectrophotometric studies. The glasses were installed in 1,00 X 1,20m openings in two façades facing north and west, separately. The colorless 4mm float glass was taken as reference. Internal surface temperatures of glasses, internal dry bulb temperatures and outdoor temperatures were collected. Solar gain factor was calculated on the basis of absortance values, obtained from spectrophotometrical nalysis, and temperature differences inside and outside the cells. Results show a high heat gain through float glasses, with the worst thermal behavior for the colorless one, followed by bronze, gray and green. Furthermore, reflective glasses obtained by vacuum metal deposition present the best thermal performance for the purpose of heat gain attenuation and to design buildings with the least energy consumption for cooling.

ASSUNTO(S)

vidro conforto termico glasses thermal comfort heat gain calor solar

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