If you’ve ever designed an overhang to protect a window, you have been confronted with the question of how far should it extend? It seems like a simple enough question, yet the factors to consider lead to ever more questions:
…which way does the window face?
…how much of the window should be protected?
…how is the overhang length related to various Sun angles?
At first blush, one may presume that the highest Sun angle above the horizon during the equinoxes (March/September 21) would generally inform an overhang length in order to provide shading for the warmer half of the year. Such simplistic criteria would generally hold true for only a south-facing window and may overlook critical needs for shading and/or solar access in a specific project scenario.
For a window at any orientation, the angle above the horizon that should govern an optimized overhang length is called the Profile Angle.