To maximise the natural light going into a building, proper orientation is essential. Because the seasonal positions of the sun are well-known, it is possible to calculate the effect of the sun on a building's proposed location and orientation. The profile angle is the angle between a line perpendicular to the plane of a window and the rays of the sun. It is used to determine the positioning of shading devices.
- Skill level:
- Moderately Challenging
Things you need
- Sun angle calculator
Determine the latitude of the structure in question.
Assemble the sun calculator. Several sun charts are available, each representing different latitudes. Locate the sun chart closest to the latitude you have identified, and attach the red transparent overlay on top of it, followed by the cursor. The red overlay is used to calculate the profile angle, but as you will most likely be making further calculations, add the cursor too.
Turn the red transparent overlay so the line marked "Normal to Window" is in line with the orientation of the window you are calculating the profile for. This is indicated on the sun chart by "Bearings from True South."
Determine the date for which you are calculating the profile angle. The sun chart only shows the path of the sun -- indicated by the curved black lines -- for the 1st, 11th and 21st of the month. If a more specific date is required for some reason, calculate manually by taking an approximate distance between these dates. For example, if you require the 6th, use the profile angle around halfway between that shown for the 1st and the 11th.
Locate the point where the sun path line intersects the sun time line for the hour of day required. This is the position of the sun.
Look at the red transparent overlay. The red line closest to the position of the sun indicates the profile angle. Like the lines representing the path of the sun, there are intervals between these red lines. If more specific information is needed for some reason, this can be calculated by inspecting the closest two red lines, and interpolating the distance between them in the same way as for the sun path lines.
Tips and warnings
- If further data is needed, such as the bearing of the sun -- azimuth, or true altitude -- leave the sun calculator with these settings, and rotate the cursor so the centre line passes over the position of the sun.
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