The shading of windows in a facade is something that can be done in many ways. In general we have horizontal systems that are very suitable on south orientations and vertical shades that are more suitable on east and west orientation. Although this is not completely true around the equator. Besides that there are many different building elements suitable as shading system.
Types of window shading We can divide the shadings in different types:
- horizontal overhangs,
- louvres (vertical and horizontal)
- movable louvres
- vertical fins (lamellas)
- movable fins
- combination of horizontal and vertical systems
In one of the first books on bioclimatic design Victor Olgyay listed in 1962 the sorts of shading and daylight systems. This list of systems described in ‘Design with climate, Bioclimatic approach to architectural regionalism’ is still used to categorize the different systems available as up to today. In the overview below the different types and the shading effect can be seen.
Horizontal shading (Source: Olgyay & Olgyay)
Vertical shading (Source: Olgyay & Olgyay)
Optimized shading or solar yield?
An optimized shading system is not the same as an optimised PV solar system. In fact it is partly a contradiction. This can be seen in some old lamella solar shading systems. In the summer with a high sun angle the lamellas shade each other and partly shade the solar cells. In general this means a much lower energy output. With a lamella that is 30 to 50% larger then the solar modules this problem can be solved.
Solar lamella is about 30% larger then the solar array. Fixed solar overhang above a window.
Shading systems for photovoltaics
Not all sun shading systems are suitable for photovoltaics. The cells in the system shouldn’t be shaded. The by Olgyav so called ‘boxtypes’ are therefore less likely to be transformed into an efficient photovoltaic system than the horizontal and vertical types. Movable (tracking) systems (both vertical and horizontal) do have the advantage that it maximizes the exposure of the cells to the direction of the sun. Finally screens and canopies are made of textiles.