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Solar access is the availability of, or access to, unobstructed, direct sunlight. Access to sunlight is important for a number of reasons, including the optimum performance of passive solar buildings and solar energy conversion devices and the availability of natural lighting (or daylighting).
Solar access issues emerged in the United States initially as a means by which a landowner could attempt to protect his/her "access," or use, of solar radiation from present or future impairment. For example, a laundry with solar water heater collectors on its roof could legally alter any nearby structural development that could cast a shadow on the collectors and negatively affect system performance.
Early efforts to protect solar access took the view that every landowner's right to natural sunlight deserved protection. It was later realized that broad solar access substantially benefited the entire community in many ways. Energy/cost savings, comfort, construction cost savings, enhanced market value, future solar energy utilization potential, and aesthetics were all improved.
Several communities in the United States have developed solar access planning guidelines and/or ordinances. Data gathering, policy determination and development, and integrating new and/or existing statutes with solar access are necessary steps in the process. Zoning is a common mechanism used to protect solar access.
Solar Site Design
The intent of solar site strategy is very simple—orient the building toward the sun to increase winter heating potential and reduce summer overheating. For new construction, facing a building within 30° of true south (or true north in the Southern Hemisphere) costs nothing, yet maximizes solar potential. Some communities suggest orientations as much as 45° east of south, since morning sunlight from the east offers many benefits with only minor increases in summer heating.
Studies by the Lawrence Berkeley National Laboratory estimate a 25%-50% reduction in annual cooling energy consumption through well-designed landscape design. Additional benefits of energy-efficient landscaping include aesthetics, environmental quality, noise buffering, privacy, and spatial definition. It is important to encourage compatibility between landscaping, shading, and solar access goals.
Solar Building Design
With optimum orientation, it is much easier to design buildings to incorporate solar features such as passive space heating and cooling and daylighting. Many solar design strategies are highly cost-effective when incorporated into the initial building design. This typically reduces costs for initial capital investment in the building heating and cooling equipment, and ongoing operating costs.
The City of San Jose, California, for example, precisely describes what constitutes a solar access dwelling unit. There, the amount of shade on the dwelling unit defines its level of solar access. According to the City of San Jose, shading from a structure and/or vegetation must not exceed the following amounts, at solar noon on December 21: 20% of the south facing walls, 10% of the south facing glazing, or 20 square feet [1.86m2] of south facing glazing.
Solar Energy Systems
Unobstructed access to the sun is necessary for the optimum performance of active and passive solar energy systems. There is generally no guarantee a solar system will always have unobstructed access to the sun. Every day, decisions about the built environment and landscape effect the future shading of existing or potential sites.
Solar access protection is clearly advantageous for the following systems in the associated locations:
- Rooftop: solar water heater and space heating collectors and photovoltaic arrays
- Walls: passive solar systems such as Trombe walls, attached solar greenhouses, and direct gain systems
- Lot (south-facing): ground-mounted or detached active collector systems.
A number of communities throughout the country have created solar access policies and regulations according to unique local situations. If a community wishes to develop a plan for protecting solar access, they must take a number of steps to achieve its goal. There are several examples of community approaches in the Resources section below.
If there are no local solar access laws, private citizens requiring access to sunlight may have to bear the cost of private solar access agreements through such devices as easements or restrictive covenants.
Zoning ordinances and building codes can create problems for solar access. Most pertain to height, setback from the property line, exterior design restrictions, yard projection, lot orientation, and lot coverage requirements. The most important solar access regulation for subdivision development is a predominantly east-west street orientation. This promotes optimal building orientation for solar access.
Credits: US Department of Energy (http://www.eere.energy.gov/consumerinfo/factsheets/ja1.html)