Properly sized and installed roof overhangs can most effectively shade south-facing windows from the summer heat. If oriented properly, overhangs will allow the sunlight in through the windows during the winter, providing more warmth to a house.

 

Overhangs on the Zion National Park Visitor Center shade the windows and prevent the sun from shining directly into the building. The length and position of the overhangs were determined based on the Zion Canyon latitude and weather patterns.

 

Construction and orientation of an overhang can be tricky since it involves many passive solar design factors:

 

• Latitude
• Climate
• Solar radiation transmittance
• Illuminance levels
• Window size and type

 

It's easy to incorporate overhangs into a home design before or while it's under construction. Adding an overhang to an existing home, however, can be quite difficult and sometimes impossible. Window awnings, louvered patio covers, or lattice-type panels can be considered as alternatives for existing homes.

 

See also roof overhang and other window coverings and treatments.