The solar-ready provisions are mandatory for single-family residential buildings that do not have a solar PV system, most commonly due to an exception to the prescriptive PV requirements in Section 150.1(c)14. There are also exceptions to the “solar zone” requirements. These are described in the corresponding sections of this chapter. These exceptions remove the need to reserve a portion of the roof area as a solar zone. However, the requirements relating to the main electrical service panel, reserved areas for inverters, metering equipment, and interconnection pathways to the electrical service will still apply. For this reason, CF2R-SRA-01-E compliance forms must be submitted with the building permit application, even when using an allowable solar zone exception.
Please note: In §110.10 of the Energy Standards, the solar zone, interconnection pathways, and design load requirements for low-rise multifamily buildings are located with the high-rise multifamily requirements in §110.10(b)1B. Refer to the multi-family buildings chapter in the “Nonresidential Compliance Manual” for more information.
The solar-ready requirements apply to newly constructed single-family homes without a PV system located in a subdivision with 10 or more residences and where the tentative subdivision map application is complete and approved by the enforcement agency.
Note, even if homes within a subdivision of 10 or more residences use an approved community solar option for compliance, they must still meet the solar-ready requirements of Section 110.10, unless they qualify for an exception.
The solar zone is a suitable place where solar panels can be installed at a future date - if the owner chooses to do so. A solar zone area is designed with no penetrations, obstructions, or significant shade. The solar zone must comply with the access, pathway, smoke ventilation, and spacing requirements in Title 24 Part 9. Requirements from the other parts of Title 24, and those adopted by a local jurisdiction, should also be incorporated in the solar zone design.
The total area of the solar zone may be composed of multiple subareas - if they meet minimum size specifications. No dimension of a subarea can be less than five feet. If the total roof area is equal to or less than 10,000 square feet, each subarea must be at least 80 square feet. If the total roof area is greater than 10,000 square feet, each subarea must be at least 160 square feet.
The solar zone must be located on the roof or overhang of the building. The “designated” solar zone’s total area must be no less than 250 square feet (§110.10(b)1A). See Figure 7-6 for some acceptable solar zone placement techniques.
There are six allowable exceptions to the required solar zone area. Exceptions 1 and 6 allow alternate efficiency measures instead of an actual solar zone, so the requirements for zone shading, azimuth, design load, interconnection pathways, owner documentation, and electric service panel do not apply.
Submit a CF2R-SRA-01-E to the building department for all projects that do not include a solar PV system, even when using an exception to solar zone requirements. In addition, submit a CF2R-SRA-02-E solar zone worksheet for all projects with a solar zone, including exceptions that allow a reduced solar zone area.
Exception 1 may apply when a domestic solar water-heating (SWH) system is permanently installed at the time of construction. The SWH system must comply with the installation criteria in the Reference Residential Appendix RA4 and have a minimum solar savings fraction of 0.50. Note: These buildings are also exempt from the interconnection pathway, documentation, and electrical panel requirements because there is no solar zone.
Exception 2 may apply if the single-family home has three or more habitable stories and a total floor area ≤ 2,000 square feet. The designated solar zone may be reduced. The area must be ≥ 150 square feet.
Exception 3 may apply if the single-family home is in the Wildland-Urban Interface Fire Area (as defined in Title 24, Part 2). The solar zone area may be reduced to ≥ 150 square feet. In addition, a whole-house fan must be permanently installed at the time of construction. This exception is intended to accommodate attic- and roof-venting requirements in these fire areas.
Exception 4 reduces the solar zone area when the roof is shaded by objects that are not part of the building project, and therefore beyond the designer’s control. The designated solar zone may be reduced to ≥ 50 percent of the potential solar zone area when solar access is limited as described below. When the “potential” solar zone is smaller than the 250 square feet minimum, the solar zone can be reduced to half the area of the potential solar zone. The reduced-size solar zone is called the “designated” solar zone.
Figure 7-2: Calculating Designated Solar Zone
Example 7-13
Question:
A house has a total roof area of 2,500 SF. The neighbor’s house and trees shade the roof, so 2,100 SF of the roof has less than 70 percent annual solar access. How big does the solar zone have to be?
Answer:
If the entire roof were to have an annual solar access of 70 percent or greater, the minimum solar zone would have been 250 SF. Since the potential solar zone is only 2,500 – 2,100 = 400 SF, however, the minimum solar zone can be reduced to 50 percent of the potential solar zone, or 200 SF.
Exception 5 allows a reduced solar zone of ≥ 150 square feet if all thermostats have demand responsive controls. See Appendix H of this compliance manual for guidance on compliance with the demand responsive control requirements.
Exception 6 allows no solar zone when the following energy efficiency features are met:
All thermostats have demand responsive controls that comply with Section 110.12(a) and Joint Appendix JA5 (please see Exception 5, above, for more details), AND
Compliance with one of the following:
Install a:
a dishwasher that meets or exceeds the ENERGY STAR® program requirements WITH a refrigerator that meets or exceeds the ENERGY STAR program requirements; or
a whole-house fan driven by an electronically commutated motor; or
an SAE J1772 Level 2 Electric Vehicle Supply Equipment (EVSE or EV Charger) with a minimum of 40 amperes. SAE J1772 is the SAE International document titled “SAE Electric Vehicle and Plug in Hybrid Electric Vehicle Conductive Charge Coupler” (SAE J1772_201710)
Install a home automation system that is capable of, at a minimum, controlling the appliances and lighting of the dwelling and responding to demand response signals; or
Install alternative plumbing piping to permit the discharge from the clothes washer and all showers and bathtubs to be used for an irrigation system in compliance with the California Plumbing Code; or
Install a rainwater catchment system designed to comply with the California Plumbing Code and uses rainwater flowing from at least 65% of the available roof area.
Example 7-14 Solar Ready Zone
Question:
What are the examples of how the solar-ready zone requirements can be avoided using Exception 6?
Answer:
Exception 6 provides three options for avoiding the solar-ready zone requirements altogether:
1. Install only demand responsive capable (DRC) thermostats with ENERGY STAR® dishwasher and refrigerator, or
2. Install only DRC thermostat(s) and a whole-house fan driven by an electronically commutated motor, or
3. Install only DRC thermostat(s) and a level 2 EV charger with a minimum of 40 amperes.
Any of these three options can be used to avoid the solar ready zone requirements.
All sections of the solar zone on steep-sloped roofs (rise-to-run ratio greater than 2:12, or 10 degrees) must be oriented between 90 degrees and 300 degrees of true north. The orientation ensures a reasonable solar exposure if a solar energy system is installed in the future. On a low-sloped roof (rise-to-run ratio equal to or less than 2:12, or 10 degrees), the azimuth requirement does not apply.
Figure 7-4: Orientation when solar zone is located on a steep-sloped roof
The solar zone must be free from roof penetrations and shall not have any obstructions such as vents, chimneys, architectural features, or roof-mounted equipment located in the solar zone. This requirement ensures that the solar zone remains clear and open for the future installation of a solar energy system.
Any obstruction located on the roof or any other part of the building that projects above the solar zone must be located at a sufficient horizontal distance away from the solar zone in order to reduce the resulting shading of the solar zone. For each obstruction, the horizontal distance (“D”) from the obstruction to the solar zone shall be at least two times the height difference (“H”) between the highest point of the obstruction and the horizontal projection of the nearest point of the solar zone.
Figure 7-5: Schematic of Allowable Setback of Rooftop
Obstructions
Any obstruction that is not located on the roof or another part of the building, such as landscaping or neighboring building, or is oriented north of all points of the solar zone is not subject to the shading requirement.
The structural design loads for roof dead load and roof live load must be clearly indicated on the construction documents for the designated solar zone areas. The structural load information will be easily available if the building owner considers a solar energy system installation in the future. It is not necessary to estimate the collateral loads for future solar energy systems.
§110.10(c)
All buildings that comply by designating a solar zone must also include a plan for connecting a future PV and SWH system to the building’s electrical or plumbing system. The construction documents must indicate:
1. A reserved location for inverters and metering equipment for solar electric systems.
2. A reserved conduit route from the solar zone to the point of interconnection with the electrical service. There is no requirement to install any conduit.
3. For homes with a central water heating system, a reserved plumbing pathway from the solar zone to the water-heating system connection. There is no requirement to install any plumbing.
§110.10(d)
A copy of the construction documents or a document containing the required solar-ready information must be provided to the occupant. The building occupant must also receive a copy of the associated installation forms CF2R-SRA-01-E and CF2R-SRA-02-E. Providing this information to the building occupant is required so the information is available if the owner decides to install a solar energy system in the future. Construction documents must include information about the as-designed structural loads, solar zone location, and the reserved interconnection pathways.
§110.10(e)
The main electrical service panel must have a minimum busbar rating of 200 amps. The panel must also include space for a future install of a double-pole circuit breaker, if one is not installed during construction, and must be permanently marked “For future solar electric”. These items are required to simplify the possible future installation of a solar electric system.