This report provides data that can be used to quantify the ability of windows and shading devices to control summertime overheating. It covers different types of glazing: external shading including overhangs and fins, screens and louvres, internal and mid-pane blinds, and combinations of the above. The data allow the designer to compare the effectiveness of different forms of shading devices, and can be used as input to simple calculation methods. A calculation tool is included on a CD-ROM that enables the effective summertime solar transmittance of windows with shading devices to be calculated, together with data on radiation.