Solar Passive Design

Design Techniques
  • Use energy-efficient design strategies.
  • Orient the building with the long axis running east/west.
  • Select, orient, and size glass to optimize winter heat gain and minimize summer heat gain for the specific climate. Consider selecting different glazings for different sides of the house.
  • Size south-facing overhangs to shade windows in summer and allow solar gain in winter.
  • Use daylight to provide natural lighting.

Window Sizing

      The shape of the building should primarily be a rectangle, with the largest axis running from east to west. The building’s southern exposure must be clear of large obstacles. Although a true southern exposure is optimal to maximize solar contribution, it is neither mandatory nor always possible. Provided the building faces within 30° of due south, south-facing glazing will receive about 90 percent of the optimal winter solar heat gain.



          Overhangs are strongly encouraged for the southern facing windows, since the summer sun rises at a higher angle. Properly sized overhangs are an effective option to optimize heat gain and shading. They shade windows from the summer sun and, in the winter when the sun is at a lower angle in the sky, allows sunlight to pass through the window to warm the interior. The following picture displays overhanging sizing rules.

  • Overhanging Sizing Rules

1.  Draw the wall to be shaded to scale.

2.  Draw the summer sun angle upward from the bottom of the glazing.

3.  Draw the overhang until it intersects the summer sun angle line.

4.  Draw the line at the winter sun angle from the bottom edge of the overhang to the wall.

5.  Use a solid wall above the line where the winter sun hits. The portion of the wall below that line should be glazed.