An analysis of absorbed radiation by domed and vaulted roofs as compared with flat roofs

Domed or vaulted roofs have been extensively used in buildings throughout the Middle East and other hot arid regions. Many studies have focused on climate-related considerations, but very little quantitative research exists in the literature. In this study, an attempt was made to calculate the insolation absorbed by these roofs, as compared with flat roofs, based on angular dependence of absorptance and solar geometry. Results showed that a domed or vaulted roof will absorb more solar radiation than its corresponding flat roof. The ratios K_b, K_tot increase with the increase of the half dome or vault angle but are insignificantly affected by climate characteristics and latitude of the location. It was also seen that a south-north facing vaulted roof both reduces the solar heat gain of buildings in summer months and increases solar heat gain in winter months compared to one which faces east-west; the greater the proportion of area exposed to the sun is, the smaller the amount of beam radiation that will be absorbed by a curved roof. Furthermore, results showed that even if absorptance is assumed to be constant this would affect total solar heat gain of the roofs studied by less than 4%.