7.6 Solar Ready Overview

The solar ready provisions are mandatory for low-rise residential buildings that do not have a PV system due to an exception in Section 150.1(c)14. There are exceptions to the “solar zone” requirements, and these are described in the corresponding sections of this chapter. Because solar ready is mandatory, CF1R-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. Because most of the low-rise multifamily requirements are identical to high-rise (including three Exceptions), Chapter 9 of the “Nonresidential Compliance Manual” is an additional resource for technical assistance.

7.6.1 Covered Occupancies

The low-rise residential solar-ready requirements only apply to new single-family homes and low-rise multifamily buildings that do not have a PV system, as described in A and B below.

The solar-ready requirements apply to the following newly constructed single-family homes without a PV system, and:

The solar ready requirements apply to low-rise multifamily buildings having three habitable stories or fewer without a PV system.

A note about Mixed Occupancy Buildings: The Energy Standards apply to mixed occupancy buildings. Low-rise buildings with nonresidential space on the ground floor and multi-family residential floors above are common examples. The Solar Zone requirements include mixed occupancy buildings.

7.6.2 Solar Zone

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.

For single-family homes, the solar zone must be located on its roof or overhang.

For low-rise multifamily buildings, the solar zone can be located on any of the following locations:

3. Roof or overhang of another structure located within 250 feet of the primary building.

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).

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 and design load; interconnection pathway, owner documentation, and electric service panel do not apply either.

Submit a CF1R-SRA-01-E to the building department with the building permit application for all projects covered by solar ready, even when using a Solar Zone Exception. In addition, submit a CF1R-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.

Exceptions for Reduced Solar Zone Due to Shade

Step 1: Determine the Annual Solar Access: For the solar ready requirements, solar access is the ratio of solar insolation including shading to the solar insolation without shading. Annual solar access is most easily determined using specialized software.

Solar Access=(Solar Insolation Including Shading)

(Solar Insolation Without Shading)

Solar access does not take into account shading from objects that are included in the building project because the designer has control of potential obstructions. Objects that are not part of the building project cannot be moved or modified as part of the project and include existing buildings, telephone poles, communication towers, trees, or other objects. Objects that are considered part of the building project are objects constructed as part of the building project and include the building itself, its HVAC equipment, outdoor lights, landscape features and other similar objects.

First evaluate whether there are any objects outside the building project that will shade the rooftop (or other prospective solar zone areas such as overhangs or parking shade structures). If an existing object is located north of all potential solar zones, the object will not shade the solar zone. Similarly, if the horizontal distance (“D”) from the object to the solar zone is at least two times the height difference (“H”) between the highest point of the object and the horizontal projection of the nearest point of the solar zone, then the object will not shade the solar zone (See Figure 7-4).

Step 2: Determine the Potential Solar Zone Area: On low-sloped roofs, the potential solar zone is the area where annual solar access is ≥ 70 percent.

On steep-sloped roofs the potential solar zone is the area where the annual solar access is ≥ 70 percent on the portion oriented between 90 and 300 degrees of true north.

Step 3: Determine the size of the designated solar zone. The designated solar zone must be ≥ 50 percent of the potential solar zone area. If the roof is shaded such that there is no potential solar zone area, then no solar zone is required. See Figure 7.1. Document the method/tools used to demonstrate that the solar access is less than 70 percent in the compliance form CF1R-SRA-02-E (Minimum Solar Zone Area Worksheet).

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 installed:

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 one of the following four measures (i – iv):

i. Install a dishwasher that meets or exceeds the ENERGY STAR® program requirements with a refrigerator that meets or exceeds the ENERGY STAR program requirements, OR one of the followings:

• 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).

ii. 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

iii. 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

iv. 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.

The solar zone requirement for low-rise multifamily buildings is located in the 2019 Energy Standards with the requirements for high-rise multifamily, hotel/motel and nonresidential buildings in §110.10(b)1B. The solar zone requirement for low-rise multifamily buildings applies to mixed occupancy buildings as well.

The solar zone must be located on the roof or overhang of the building, or on the roof or overhang of another structure located within 250 feet of the building, or on covered parking installed with the building project. The solar zone’s total area must be ≥ 15 percent of the building’s total roof area. Subtract any skylight area when calculating the roof’s total area.

Four solar zone exceptions apply to low-rise multifamily buildings in the 2019 Energy Standards. Exception 3 allows a smaller solar zone under certain circumstances. Exceptions 4 and 5 allow alternate efficiency measures in lieu of a solar zone. Therefore, the requirements for solar zone shading, azimuth and design load; interconnection pathway, and documentation do not apply.

Exception 3 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 reduced-size solar zone is called the “designated” solar zone. The designated solar zone may be reduced to ≥ 50 percent of the potential solar zone area when solar access is limited. Solar access is the ratio of solar insolation including shade to amount of solar insolation without shade. Shading from obstructions on the roof or other parts of the building cannot be included to determine annual solar access.

See Figure 7-2 for more information about calculating the designated solar zone.

• Low-sloped roof: the potential solar zone area is the total area of any roof where annual solar access is 70% or greater.

• Steep-sloped roof: The potential solar zone area is the roof area where annual solar access is 70% or greater and oriented between 90 and 300 degrees of true north.

Exception 4 says multifamily residential buildings do not need a solar zone if all thermostats have demand responsive controls that comply with Section 110.12(a) and Joint Appendix JA5. See Exception 5 for single-family homes (above) for more thermostat details. In addition to the compliant thermostats, choose A or B below:

A. One of the following four measures installed in each dwelling unit (i. – iv.):

i. Install 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.

ii. Install a home automation system that complies with §110.12(a) and is capable of, at a minimum, controlling the appliances and lighting of the dwelling and responding to demand response signals; or

iv. Install a rainwater catchment system designed to comply with the California Plumbing Code and that uses rainwater flowing from at least 65 percent of the available roof area.

B. Meet the Title 24 Part 11, Section A4.106.8.2 requirements for electric vehicle charging spaces.

Exception 5 includes low-rise multifamily buildings and says a solar zone is not required when the roof is designed and approved to be used for vehicular traffic, or parking, or a heliport.

7.6.3 Azimuth (Solar Zone)

For both single-family residential and low-rise multifamily buildings, all sections of the solar zone on steep-sloped roofs (ratio of rise to run of greater than 2:12) must be oriented between 90 degrees and 300 degrees of true north. The orientation is important because it ensures a reasonable solar exposure if a solar energy system is installed in the future. On a low-sloped roof (ratio of rise to run of 2:12 or less), the azimuth requirement does not apply.

7.6.4 Shading (Solar Zone)

For both single-family residential and low-rise multifamily buildings, 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.

Any obstruction oriented north of all points of the solar zone is not subject to the shading requirement. Any obstruction that is not located on the roof or another part of the building, such as landscaping or neighboring building, is not subject to the shading requirement.

7.6.5 Structural Design Loads (Solar Zone)

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.

The structural design loads requirement applies to the solar zone on both single-family residential and low-rise multifamily buildings.

7.6.6 Interconnection Pathways

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 single family residences, and multifamily buildings 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.

This requirement applies to both single-family residential and low-rise multifamily buildings.

7.6.7 Documentation

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 compliance forms CF1R-SRA-01-E and CF1R-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. This requirement applies to both single-family residential and low-rise multifamily buildings.

7.6.8 Main Electrical Service Panel

This requirement applies only to single-family residential buildings. The main electrical service panel must have a minimum Busbar rating of 200 amps. The panel must also include space to install a double-pole circuit breaker in the future, if one is not installed during construction. These items are required to simplify the possible future installation of a solar electric system.