Effect of various factors on the shading coefficient of different types of glazing

Abstract

This is a study of the effects of various factors on the shading coefficient of different types of glazing. The main objective is to investigate the sensitivity of the shading coefficient to these factors and hence the validity of adopting a fixed value for the coefficient, as given in pertinent references, under different conditions. The study covers single and double glazing, of clear or heat-absorbing glasses, with and without reflective surface coatings. Plastic glazing is also included in the work. The variations of the shading coefficient with the incidence angle, the outdoor wind velocity, and the indoor air velocity are presented for the different types of glazing. The effect of windowpane(s) treatment, by applying reflective coats, is also exposed. The study revealed that, under certain conditions and with certain types of glazing, the use of the constant shading-coefficient values available in the literature may entail untolerable error in estimating the solar heat gain through glazed fenestration. In such cases the shading coefficient may have to be treated as a variable rather than a constant. However, this incurs excessive computational effort; therefore, it can be justified only when a high degree of accuracy is required which is not the case for routine air conditioning load estimations.