The solar zone is an allocated space that is unshaded, un-penetrated, and free of obstructions. It serves as a suitable place that solar panels can be installed at a future date.
For single family residences the solar zone shall be located on the roof or overhang of the building.
For low-rise multifamily buildings the solar zone can be located at any of the following locations:
•Roof of building
•Overhang of the building
•Roof and overhang of another structure located within 250 feet (75 meters) of the primary building
•Covered parking installed with the building project
•Other structures include, but are not limited to, trellises, arbors, patio covers, carports, gazebos, and similar accessory structures.
The solar zone design must comply with the access, pathway, smoke ventilation, and spacing requirements as specified in Title 24, Part 9 or in any requirements adopted by a local jurisdiction. These additional requirements are located in other Parts of Title 24 including Parts 2, 2.5, and 9 that are adopted by the California Building Standards Commission as part of the California Building Standards Code.
The total area of the solar zone may be composed of multiple sub-areas. No dimension of a sub-area can be less than five feet. If the total roof area is equal to or less than 10,000 square feet (1,000 square meters), each sub-area must be at least 80 square feet (8 square meters). If the total roof area is greater than 10,000 square feet (1,000 square meters), each sub-area must be at least 160 square feet (16 square meters).
A. Single Family Residences
The solar zone shall be located on the roof or overhang of the building. The solar zone shall have a total area that is no less than 250 square feet (25 square meters). There are multiple exceptions, as described below, to the required total solar zone area. For Exceptions 1, 2 and 7 below, although the language in the Standards implies that these three exceptions only apply to the solar zone requirements, the intent of the Standard is for the exceptions to apply to the solar zone requirement as well as the interconnection pathway requirements described in Section 110.10(c), the documentation requirements described in Section 110.10(d), and the electric service panel requirements described in Section 110.10(e).
Exceptions
1. Single family residences are exempt from the solar zone, interconnection pathway and documentation requirements if a solar PV system with a nameplate direct current (DC) power rating, of 1000 watts or greater is permanently installed at the time of construction. The nameplate rating must be measured under Standard Test Conditions. The permanently installed solar electric system is not required to be located on the roof of the building. To verify compliance with this exception form CF2R-SPV-01-E Certificate of Installation: Photovoltaic Systems must be submitted.
2. Single family residences are exempt from the solar zone, interconnection pathway and documentation requirements if a domestic solar water-heating system is permanently installed at the time of construction. The SWH system must comply with the installation criteria in the Reference Residential Appendix RA4.4.21 and having a minimum solar savings fraction of 0.50 is permanently installed at the time of construction. This is the equivalent of the prescriptive solar water-heating system requirements when installing an electric-resistance storage or instantaneous water heater serving an individual dwelling unit. The permanently installed domestic solar water-heating collectors are not required to be located on the roof of the building. To verify compliance with this exception form CF2R-STH-01-E Certificate of Installation: Solar Water Heating System must be submitted.
3. The solar zone may be reduced to no less than 150 square feet (15 square meters) for single family residences with three stories or more and with a total floor area equal to 2,000 square feet (200 square meters) or less.
4. The solar zone may be reduced to no less than 150 square feet (15 square meters) for single family residences with a whole house fan and where the residence is located in climate zones 8 through 14 and where the residence is located in the Wildland-Urban Interface Fire Area (as defined in Title 24, Part 2). This exception is to accommodate attic and roof venting requirements in these fire areas.
5. The solar zone may be reduced to 50 percent of the potential solar zone area. For the purpose of the Standards, the potential solar zone area is the total area of the roof where annual solar access is 70 percent or greater. This exception reduces the required solar zone area when the roof is shaded by objects which are not located on the roof or any other part of the building. If the potential solar zone is smaller than the minimum solar zone area specified in §110.10(b)1A of 250 square feet, then the solar zone can be reduced to half the area of the potential solar zone. If the roof is shaded such that there is no potential solar zone area, then no solar zone is required.
For purposes of the solar ready requirements, solar access is the ratio of solar insolation including shading to the solar insolation without shading.
Objects that are excluded from the building project are objects that will not be moved or modified as part of the building project and include existing buildings, telephone poles, communication towers, trees, or other objects. Objects that are included in the building project are objects that will be constructed as part of the building project and include the building itself, HVAC equipment on the building, parking lot lights, and other similar objects. As mentioned, solar access does not take into account shading from objects that are included in the building project as the designer has control of the location of these potential obstructions.
Annual solar access is most easily determined using an instrument that is equipped with a camera with a fisheye lens and specialized imagery processing software. The instrument can calculate the annual solar access of any point on a proposed site based on the location of the building and information that is captured in the digital photograph. Since this type of instrument relies on photographs, their most appropriate use is to determine solar access on existing buildings. The instruments are not as useful in the design phase for newly constructed buildings when capturing a digital photograph from the proposed solar zone location is not feasible.
To determine the annual solar access during the design phase, designers will first evaluate whether there are any objects external to 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 to the 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 7-1).
If objects external to the building project could shade the solar zone, annual solar access can be quantitatively determined using several computer-aided design (CAD) software packages which can import a CAD file of the building and perform a shading analysis or several online solar quoting tools can be used which make use of both overhead and orthogonal aerial imagery. Annual solar access can be qualitatively determined using several three-dimensional modeling programs. The method/tools used to quantify that the solar access is less than 70 percent (and reduce the potential solar area) shall be documented in compliance form CF1R-SRA-02-E.
Example 7-1
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. However, the since the potential solar zone is only 2,500 – 2,100 = 400 SF, the minimum solar zone can be reduced to 50 percent of the potential solar zone, or 200 SF.
6. The solar zone may be reduced to no less than 150 square feet (15 square meters) if all thermostats in the residence are Occupant Controlled Smart Thermostats (OCST) with communications capabilities enabled to receive and respond to Demand Response signals. An OCST is a setback thermostat with communication capabilities that enable the occupant to receive Demand Response related messages and respond to those signals by automatic adjustment of the thermostat setpoint as described in Joint Appendix JA5 (subject to occupant participation). Enabling communications capabilities requires that the OCST has one of the following: onboard communications capabilities, an installed communications module for OCSTs with removable communications module(s), or an installed communications gateway for an OCST where an external gateway is required for communications.
7. Single family residences are exempt from the solar zone, interconnection pathway and documentation requirements if all of the following conditions are met:
a. All thermostats in the residence are OCST with communications capabilities enabled to receive and respond to Demand Response signals (subject to occupant participation). Enabling communications capabilities requires that the OCST has one of the following: onboard communications capabilities, an installed communications module for OCSTs with removable communications module(s), or an installed communications gateway for an OCST where an external gateway is required for communications.
b. All permanently installed indoor lighting is high efficacy and is installed in kitchens, bathrooms, utility rooms, and garages at a minimum. Permanently installed nightlights complying with Section 150.0(k)1E and lighting integral to exhaust fans complying with Section 150.0(k)1F are allowed.
c. All permanently installed lighting in bathrooms is controlled by a vacancy sensor, except for one high efficacy luminaire with total lamp wattage no greater than 26 watts.
d. Every room which does not have permanently installed lighting has at least one switched receptacle installed.
e. All permanently installed outdoor lighting is high efficacy and controlled by an on/off switch and either a photocontrol or astronomical time clock or energy management control system.
B. Low-rise Multi-family Buildings
The solar zone shall be located on the roof or overhang of the building or on the roof or overhang of another structure located within 250 feet (75 meters) of the building or on covered parking installed with the building project. Other structures include, but are not limited to, trellises, arbors, patio covers, carports, gazebos, and similar accessory structures. The solar zone shall have a total area that is no less than 15% of the total roof area of the building after subtracting any skylight area from the roof area. There are multiple exceptions, as described below, to the required total area. For Exceptions 1, 2, 4 and 5 below, although the language in the Standards implies that these four exceptions only apply to the solar zone requirements, the intent of the Standard is for the exceptions to apply to the solar zone requirement as well as the interconnection pathway requirements described in Section 110.10(c), and the documentation requirements described in Section 110.10(d),
Exceptions
1. Buildings are exempt from solar zone, interconnection pathway and documentation requirements if a solar electric system with a nameplate DC power rating of no less than 1 watt per square foot of roof area is permanently installed at the time of construction. The nameplate rating must be measured under Standard Test Conditions, The permanently installed solar electric system is not required to be located on the roof or overhang of the building or on the roof or overhang of another structure. To verify compliance with this exception form CF2R-SPV-01-E Certificate of Installation: Photovoltaic Systems must be submitted.
2. Buildings are exempt from solar zone, interconnection pathway and documentation requirements if a domestic solar water-heating system complying with Section 150.1(c)8Ciii is permanently installed at the time of construction. This is the equivalent of the prescriptive solar water-heating system requirements when installing a water-heating system serving multiple dwelling units. The permanently installed domestic solar water-heating collectors are not required to be located on the roof or overhang of the building or on the roof or overhang of another structure. To verify compliance with this exception form CF2R-STH-01-E Certificate of Installation: Solar Water Heating System must be submitted.
3. The solar zone may be reduced to 50 percent of the potential solar zone area. The potential solar zone area is the total area of the roof where annual solar access is 70 percent or greater. This exception reduces the required solar zone area when the roof is shaded by objects which are not located on the roof or any other part of the building. If the roof is shaded such that there is no potential solar zone area, then no solar zone is required. For a detailed discussion of annual solar access, see Exception 5 under Single Family Residences.
4. Low-rise multifamily buildings that comply with items (a) through (e) below are exempt from solar zone, interconnection pathway and documentation requirements.
a. All thermostats in each dwelling unit are Occupant Controlled Smart Thermostats (OCST) with communications capabilities enabled to receive and respond to Demand Response signals. An OCST is a setback thermostat with communication capabilities that enable the occupant to receive Demand Response related messages and respond to those signals by automatic adjustment of the thermostat setpoint as described in Joint Appendix JA5 (subject to occupant participation). Enabling communications capabilities requires that the OCST has one of the following: onboard communications capabilities, an installed communications module for OCSTs with removable communications module(s), or an installed communications gateway for an OCST where an external gateway is required for communications. OCST must be certified by the Energy Commission to meet the requirements described in the Joint Appendix JA5.
b. All permanently installed indoor lighting in each dwelling unit is high efficacy and is installed in kitchens, bathrooms, utility rooms, and private garages at a minimum. Permanently installed nightlights complying with Section 150.0(k)1E and lighting integral to exhaust fans complying with Section 150.0(k)1F are allowed.
c. All permanently installed lighting in bathrooms is controlled by a vacancy sensor, except for one high efficacy luminaire with total lamp wattage no less than 26 watts.
d. Every room which does not have permanently installed lighting has at least one switched receptacle installed.
e. All permanently installed outdoor lighting for private patios, entrances, balconies, and porches is high efficacy and controlled by an on/off switch and either a photocontrol or astronomical time clock or energy management control system.
5. Buildings are exempt from solar zone interconnection pathway and documentation requirements if the roof is designed for vehicle traffic (parking lot) or if the roof is designed as a helicopter landing zone.
For both single family residences and low-rise multi-family buildings, all sections of the solar zone on steep-sloped roofs (ratio of rise to run of greater than 2:12) shall be oriented between 110 degrees and 270 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.
If a solar zone is located on a low-sloped roof (ratio of rise to run less than 2:12), the orientation requirement does not apply.
For both single family residences and low-rise multi-family buildings, the solar zone shall 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.
For both single family residences and low-rise multi-family buildings, any obstruction located on the roof or any other part of the building that projects above the solar zone shall 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 (see following equation).
Equation 7.1 D ≥ 2 X H
Any obstruction oriented north of all points of the solar zone is not subject to these requirements. Any obstruction which is not located on the roof or another part of the building, such as landscaping or a neighboring building is not subject to these requirements.