For home designers, understanding exceptions to prescriptive PV (photovoltaic) requirements is crucial. This article covers the concepts of annual solar access, effective annual solar access, effective annual solar access roof areas, and solar access roof area (SARA). Additionally, it outlines five key exceptions that may apply in cases of limited unshaded roof space, small minimum PV system sizes, compliance with snow load requirements, mandatory conditions for approval, and buildings with battery storage systems. This article is specific to the 2022 Title 24 energy code (effective beginning January 1, 2023).
As a home designer, you're likely aware of the importance of incorporating solar power systems in your designs to meet energy efficiency standards. However, you may encounter situations where adhering to photovoltaic (PV) requirements isn't feasible or necessary. In this blog post, we'll discuss the concepts related to solar access and delve into five key exceptions that can impact your home designs.
Understanding Solar Access Terminology
Before diving into the exceptions, let's clarify some terms related to solar access:
Annual Solar Access: The ratio of solar insolation (including shading) to solar insolation without shading. Check Section 7.6.2 for calculating solar access when shading is a factor.
Effective Annual Solar Access: The annual solar access must be at least 70% of the output of an unshaded PV array.
Effective Annual Solar Access Roof Areas: Roof areas that satisfy the effective annual solar access requirements and have at least 80 contiguous square feet.
Solar Access Roof Area (SARA): The area of the building's roof and other structures (covered parking areas, carports, etc.) that can structurally support a PV system according to Title 24, Part 2, Section 1511.2. SARA excludes roof areas with less than 70% annual solar access.
Five Key Exceptions to PV Requirements
Now that we have a better understanding of solar access terms, let's explore the exceptions to PV requirements:
Exception 1: Applies to limited unshaded roof space. Steep slope roofs with a northerly azimuth between 300 and 90 degrees from true north are not considered for SARA. If the SARA is less than 80 contiguous square feet, no PV system is required.
Exception 2: No PV system is needed if the minimum PV system size is less than 1.8 kWdc.
Pro-tip: Not sure if the minimum PV system size is less than 1.8 kWdc? Try using our Solar PV Sizing Calculator at the bottom of this article.
Exception 3: Applies to buildings with enforcement-authority-approved roof designs where it's impossible for the PV system to meet the snow load requirements specified in Ch. 7 of the ASCE Standard 7-16.
Exception 4: For buildings approved by the local planning department before January 1, 2020, with mandatory conditions for approval:
Shading from steep-sloped roof designs required by the mandatory conditions shall be considered for annual solar access calculations.
Roof areas disallowed for PVs by the mandatory conditions shall not be considered when determining the SARA.
Exception 5: Applies to buildings with battery storage systems. PV system sizes calculated using equation 150.1-C can be reduced by 25% if installed alongside a battery storage system meeting the requirements specified in Joint Appendix JA12 and having a minimum usable capacity of 7.5 kWh.
With a clear understanding of these exceptions, home designers can better navigate PV requirements and optimize their designs for energy efficiency, even when faced with challenging constraints.
C&S Energy Pro is committed to getting a fast turnaround on your Title 24 documents which will help ensure construction projects are completed on time and that consumers will be able to move into their homes quicker. Avoid the hassle of long wait times generally associated with Title 24 documentation and call us today!
Solar PV Sizing Calculator
Not sure if the minimum PV system size is less than 1.8 kWdc? Try using our Solar PV Sizing Calculator below to find out!
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