Performance analysis of external shading devices

Abstract The performance of the basic vertical and horizontal types of external shading devices was studied in detail. The different performance modes are presented in the form of shading masks featured by the cutoff angles. Mathematical formulae were derived to express the cutoff angles in terms of the various geometrical parameters characterizing the combination of the shading device and the fenestration. These angles define the partial and complete shading phases. The formulae are put in generalized forms, in terms of normalized geometrical ratios, so as to be independent of the absolute dimensions. A unified approach was followed for both vertical and horizontal devices so that the derived normalized expressions can be adopted for the two types. The effect of the various geometrical factors on the cutoff angles, i.e. on the form of the shading mask, was investigated for different configurations of vertical and horizontal shades. Based on the derived relations, the trends of variation, of the cutoff angles with these factors, are graphically presented for each case.