Solar Ready Construction Guidelines

These voluntary guidelines have been developed for the local governments of the OKI region to provide guidance for residential developers, home builders and architects in the design and construction of new residential buildings.  These guidelines are intended to guide a developer, architect, or other interested party through the components of building design required to prepare a building for future solar installation.  These guidelines include best practices for solar-ready building design to minimize the costs of future solar installation while maximizing potential system efficiency and apply to site selection, building design, and building construction.

Site Considerations

Building and Roof Orientation   Buildings should be oriented to afford a south-facing roof and designed in a way that maximizes future solar panel access to sunlight.

Avoid Shading   Buildings should be designed in such a way that solar panels will not be shaded by nearby structures or trees to the south.  Proximity of the building site to any existing shade trees should be considered, however, in situations where shade exists at time of construction should not necessarily deter from Solar Ready construction understanding that the service of the structure will potentially surpass the lifespan of the tree(s).

Roof Design Considerations

Preserve Rooftop Space for Solar Collectors The south-facing portion of the roof should include a contiguous area, free of rooftop obstruction, of sufficient size to allow for a solar system. At minimum, an area of several square feet (100 sq. ft. per kW) should be identified. Typical residential rooftop PV systems are 5-10kW in capacity, therefore, roof space of 500-1000 sq. ft. is ideal.

Flat Roof Configuration For flat roofs, designers should ensure that the building has adequate roof access, and should consider integrating rooftop safety equipment such as guardrails when appropriate. The area identified for solar collection should be near the middle of the roof, away from any parapets to avoid shading. Any rooftop HVAC equipment should be positioned to avoid conflicting with the location of, or shading the solar collectors.

Pitched Roof Configuration For pitched roofs, designers should take into account the degree of pitch that would maximize the generation of solar panels located flush against the roof. In the OKI region, an optimal roof pitch for solar is slightly less than 38°, or a 9:12 pitch.

Allow for additional weight The roof should be adequately reinforced to allow for the additional weight, including both the weight of the solar systems itself and the impact of wind and snow loads. Solar PV systems add 3-6 lbs. per square foot to the dead load of a roof, and up to 45 lbs. at specific attachment points. If a ballasted system is installed on a flat roof, it may add up to 20-30 lbs. per square foot to the roof’s dead load.

Record Roof Reinforcements  Any reinforcements to the roof should be recorded on official drawings, such as the code sheet, for the benefit of solar developers.

Record Potential Layouts  Provide detailed drawings and potential layouts to code officials for filing.  Future homeowners and/or contractors will benefit from understanding the design intentions.

Roof Warranty   Determine if any material or installation warranties would be jeopardized with a future PV installation and document findings for homeowner records.

Electrical and Mechanical Considerations

Reserve Wall Space for Inverter   A 3’x3’ (some guides say 4’x4’) area of wall space next to the building’s main electrical panel, with an additional 3’ of clearance space in front of the wall, should be reserved for the installation of an inverter. To minimize voltage loss, the meter box and reserved inverter space should be located just below the rooftop space reserved for the solar collector.

Install Conduit    Metallic conduit at least 2” (some guides say 1”) in diameter should be installed that will run through the building from the area identified for the inverter to the area identified for the solar collector.

Leave Room for PV Breaker    The electric panel should include the necessary space for a power input breaker at the opposite end of the electric service panel from the main breaker.

Provide Adequate Home Electrical Service   Electrical service of at least 200 amperes in residential buildings is preferable to ensure that PV power generation can be accommodated.

Label Equipment and Reserved Spaces   Clearly label any conduit, wall space reserved, and reserved breaker space for future solar PV installation.