First purpose of window overhangs is shading. For that purpose we either have to calculate the dimensions of the overhang or use 3D modelling software (Sketch-Up) to study the dimensions. Because of the side-effect we will need an overhang that is much wider then the window.
The effect of fixed overhangs on windows.
Window overhang calculation.
Horizontal devices, e.g. projecting eaves, a horizontal canopy or awning, or horizontal louvres. These are characterised by a vertical shadow angle (VSA). One large or several small elements may give the same performance, the same VSA. Their shading mask will be of a segmental shape.
Figures to explain the sun calculation of an overhang.
The vertical shadow angle (VSA) is measured on a plane perpendicular to the building face. VSA can exist only when the HSA is between -90° and +90°, i.e. when the sun reaches the building face considered. When the sun is directly opposite, i.e. when AZI = ORI (HSA = 0°), the VSA is the same as the solar altitude angle (VSA = ALT). When the sun is sideways, its altitude angle will be projected, parallel with the building face, onto the perpendicular plane and the VSA will be larger than the ALT.
Window overhang modelling.
In the 3D modelling software, the location and orientation can be added to get the real sun-angles. Even a very simple model gives already insight in the shading effect.
Shadow pattern at 01 June 09:00 and 12:00 hours (location Pikerni).
Shadow pattern at 01 June 14:00 hours. The solar module is just starting to receive shadow by the building as well (location Pikerni).
Application of shading overhang SE02-D1.
The location of the demonstration building in Pikermi is not the best possible. But this situation will happen many times as only a few buildings will have a perfect orientation. For the application of the solar overhang SE02-D1 the 3D modelling software was used. As shading is important during the cooling season, the months from May to September are modelled. What came out is that the system is effective from around 10 in the morning.
Shading pattern at 10:00 in the morning for 01 April and 01 May.
Shading pattern at 10:00 in the morning for 01 June and 01 July. Because of the summer solstice both are almost the same.