An alternative general method to evaluate the atmospheric down-welling radiation

The importance of atmospheric down-welling radiation in studying building thermal environments and energy performance has been well identified, and empirical formulae to evaluate atmospheric down-welling radiation values developed with their inadequacies. In this paper, a study of developing an alternative general method for evaluating atmospheric down-welling radiation values to the water pond-based empirical formula by Clark and Allen is reported. The validity of the alternative general method has been demonstrated by comparing the atmospheric down-welling radiation values evaluated using the alternative general method and that using the Clark and Allen's formula. Since the alternative general method developed is based on a building roof system, and no water is involved, the alternative general method developed in this paper appears to have more advantages. On one hand, this could eliminate any potential impacts on prediction accuracy when water is used in different climates. On the other hand, the application of the alternative general method is relatively easier as only a suitable existing roof system is required. Therefore, the use of alternative general method can provide a more reliable and economic alternative in evaluating atmospheric down-welling radiation, when compared to using Clark and Allen's empirical formula. Practical application The alternative general method developed for evaluating atmospheric down-welling radiation values in this paper could be used as an alternative to the empirical formula proposed by Clark and Allen and is valid for all climate conditions and easy to be implemented to evaluate alternative general method values. It can be used when evaluating building night sky cooling, building passive cooling system, etc.