Site orientation and landscaping have a large impact on how energy-efficient a home will be. The sun is the main source of heat in all homes. By looking at how houses receive sunlight, site orientation can help optimize how much solar energy is available to heat a house.
Features that help to conserve the natural environment of a home or development site include:
- Orienting lots to best manage energy and light from the sun
- Planning land use that preserves the natural environment and minimizes disturbance
- Designing the site to minimize erosion, paved surfaces and runoff
- Preserving and protecting trees and natural vegetation
(“Residential Buildings: Site Design”. Energy Efficiency and Renewable Energy. Accessed 25 March 2009.)
If possible, the longer axis of the building, also known as the ridge line, should be oriented running east/west. By facing the ridge line in that direction, the longer dimension of your home faces sunny south. The optimum position for maximum solar benefits is true south but you can vary the orientation within 20 degrees of that direction with minimal effect.
In most parts of the U.S., however, just making the building the right shape, properly placing its windows and pointing it in the right direction can cut the building's total energy use by 30 percent- 40 percent at no extra cost.
Areas which are most frequently used should be located on the longer, south side of the building, where sunlight can enter through windows in the south side, high clerestories windows or skylights. The shorter east/west side reduces the amount of surface area exposed to the sun and cuts down of heat gain.
Landscape features such as trees, rocky outcroppings, small hills or water can impact how a home performs.
Become familiar with the prevailing winds and the pattern of air movement on a property - this knowledge will help you use trees and other natural features to direct summer breezes into the house while channeling cold winter winds away from it.
- Evergreen trees or a sheltering hilly outcropping on the north can buffer winter winds and harsh weather.
- Deciduous trees placed on the south and east or west can shade a home in the summer before dropping their leaves in the winter to let the sunlight into a home.
(“Passive Solar Design – Proper Orientation”. Consumer Energy Commission: California Energy Commission. Accessed 25 March 2009.)
Roofs with overhangs should shade and protect windows and doors and be sized to account for differences in the angles of the sun during the winter and summer months. Overhangs may take the form of eaves, porches, or other design features such as awnings, pergolas, or trellises. (A helpful passive solar overhang calculator based on the latitude and longitude of a home can be found here.)
Reliance on any form of shading is not nearly as important when windows with a low solar-heat-gain coefficient are used. Using a low-solar-gain low-E coating results in great energy cost reductions for air conditioning, even with no shading. This is because the glazing itself provides the necessary control of solar radiation, so shading measures become less important in terms of energy use. However, in homes designed for passive solar heating, overhangs help to control seasonal heat gain and a low SHGC can be detrimental.
For a description of the interactions between window performance and shading, see the Efficient Windows Collaborative Web site at www.efficientwindows.org.
(“Building America Best Practices Series: Volume 3”. U.S. Department of Energy, August 2005. pp. DES-24. Accessed 17 June 2009.)
Passive Solar Design
This link is to a EERE fact sheet and includes information on what to consider, costs, window selection, overhangs, and helpful diagrams.
Passive Solar Overhang Calculations
A person with basic contruction knowledge can properly design an overhang to take advantage of solar gain in the winter and have proper shading to reduce solar radiation in the summer. (The latitude and longitude for the home is needed for this calculation and can be found using various search engines, such as google.)