Design Philosophy & Regenerative Practice
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The sun is the primary energy source for every passive solar building. Understanding how the sun moves through the sky at your latitude is essential for designing a building that captures its energy in winter and rejects it in summer.

The sun’s position in the sky at any given time and location can be described by two angles: altitude (the angle above the horizon) and azimuth (the compass direction of the sun). These angles change throughout the day as the earth rotates, and throughout the year as the earth orbits the sun. In the northern hemisphere, the sun is always in the southern sky — it rises in the south-east, reaches its highest point due south at solar noon, and sets in the south-west. In summer, the sun rises high in the sky and the solar day is long. In winter, the sun follows a lower arc, rising and setting closer to south, and the solar day is shorter.

This seasonal variation is the key to passive solar design. South-facing glazing (in the northern hemisphere) receives direct sun when it is low in the winter sky, but not when it is high in the summer sky — especially if a roof overhang of the correct depth is provided. The overhang angle can be calculated precisely for any latitude to block the high summer sun while allowing the low winter sun to enter the building. This is one of the most elegant and precise relationships in all of building science.

Solar Geometry at a Glance — Northern Hemisphere

• The sun is always in the southern sky. Orient the building to face south.

• Summer sun angle is high (up to 75° above horizon at summer solstice at 40° latitude).

• Winter sun angle is low (as low as 27° above horizon at winter solstice at 40° latitude).

• A properly sized roof overhang blocks summer sun while admitting winter sun.

• In the southern hemisphere, reverse all directions — orient to face north.