To design a horizontal shading device, simply following the following steps.
- Determine cut-off date.
This is the date before which the window is to be completely shaded and after which the window will be only partially shaded.
- Determine Start and End Times.
These represent the times of day between which full shading is required. Keep in mind that the closer to sunrise and sunset these times are, the exponentially larger the required shade.
- Look up Sun Position.
Use solar tables or a sun-path diagram to obtain the azimuth and altitude of the sun at each time on the cut-off date.
- Calculate HSA and VSA.
Using the formulae given above, calculate the HSA and VSA at each time.
- Calculate Required Depth and Width.
Once again, using the formulae above, calculate the depth and width of the required shade on each side of the window.