Solar Changes Roof Designs

Solar Changes Roof Designs

While installing solar panels is not a requirement of the latest Title 24 code, builders must set aside 250 sq. ft. of roof space for them.

This is the second is a series on how new Title 24 building code requirements are affecting homebuilders in California—and possibly beyond.

For the first time in California, new homes are to be “solar-ready,” meaning their roofs are prepared for future installation of solar energy systems. There are no infrastructure-related requirements in the code, such as installation of conduit, piping, or mounting hardware. However, there are some concerns with meeting the requirements in all housing situations.


“The intent of the solar ready requirements is to provide a penetration free and shade free portion of the roof. This will help ensure that a future installation of a solar energy system is not limited by the original design and layout of the building and its associated equipment. There are no infrastructure related requirements such as installation of conduit or piping, inclusion of collateral structural loads, or pre-installed mounting hardware,” says Amber Pasricha Beck, public information officer for California Energy Commission.


“The solar ready requirements are mandatory for newly constructed single family residences in subdivisions of 10 or more homes, multifamily buildings and hotels or motels with ten stories or less, and all other nonresidential buildings with three stories or less.

For single family residences the basic requirement calls for a roof to have a 250-square-foot solar zone that is free of roof penetrations and is unshaded, while multifamily and nonresidential buildings must have a solar zone that covers 15 percent of the total roof area.

Mike Hodgson of ConSol energy consultants says California builders are constructing four model homes in subdivisions of 10 or more homes so they can show that the design works in all four cardinal points and still have have the right amount of roof space available to the sun’s rays.

The amount of space required for solar panels 
must be free of other obstructions.

Space For Solar?

However, builders could be hampered by the square-footage because of the trend of building up instead of out and that roof penetrations need to be located precisely. “If you’re trying to vent a bathroom or a kitchen, it cannot be in that 250 square feet. It’s not a difficult requirement to meet, but builders need to make sure they’re doing it correctly,” Hodgson says.

Robert E. Raymer, the Senior Engineer/Technical Director for the California Building Industry Association says that getting to that 250-sq-ft requirement could become a problem for builders planning condominiums or other high density residential structures.

“As you go vertical, roofs gets smaller—presenting some real interesting design problems,” he says.

Trading credits

There are ways to either get around the solar requirements, or use solar to get around other requirements. Title 24 relies on “credits” for each act of compliance with the code. The code allows credits to lower the overall compliance margin of a home. This means a particular measure with a large credit can be used to offset any deficit that may result from other features in the house, and still achieve compliance with the standards. For example: The solar zone may be reduced to no less than 150 square feet if all thermostats in the residence are Occupant Controlled Smart Thermostats (OCST).

However, the credit “trade-off” is only available in certain climate zones (9 through 15), to which the California Homebuilding Foundation takes exception. Climate zones 1 through 8 and 16 are not eligible for this credit, but the solar-ready requirement is in place for those zones.  The CHB also takes exception to the size of the credit, which remains the same regardless of the size of the system as long as it is about 2kW.

You can read the entire CHF impact study

The requirements also include:

  • Solar Zone – Minimum area of 250 sq. ft. reserved for solar, if multiple sections make up the solar zone, no section should be smaller than 80 ft2 and no dimension smaller than 5 ft.
  • Orientation – Solar zone on slope 2:12 or greater must be oriented between 110 degrees and 270 degrees of true north.
  • Shading – Obstructions on the roof must be a distance two times the height of the obstruction from the zone, with the exception of obstructions to the north of all parts of the solar zone.
  • Documentation
  • A location specified for inverters and metering equipment.
  • A pathway for routing conduit from solar zone to point of connection.
  • A pathway for routing plumbing from the solar zone to the water heating system. The conduit itself is not required.
  • Main Electrical Service Panel – (single family only) minimum busbar rating of 200 amps and a reserved space for the installation of a double pole circuit breaker.

Related: How Much Will Title 24 Cost?

There are some exceptions as well, mainly if they fall within two or more requirements.

  • The “solar zone” isn’t required if a permanent solar electric system of 1,000 watts or more is installed at construction.
  • No zone required if a domestic solar water heating system is installed at construction and complies to other criteria set out in the codes. 
  • Only 150 sq ft is required if a building is three stories or more and has 2,000 sq ft or less of total floor area.
  • Only 150 sq ft is required if there is a whole house fan and the residence is within the Wildland-Urban Interface Fire Area. This exception is to accommodate attic and roof venting requirements in these fire areas.
  • Solar zone can be reduced to 50 percent of the potential solar zone area, meaning the total area of the roof, where annual solar access is 70 percent or greater (confused? see Residential Manual Section 7.3.1.A.5, page 7-4 for an explanation).
  • The solar zone may be reduced to no less than 150 sq ft if all thermostats in the residence are Occupant Controlled Smart Thermostats (OCST).

About The Author

Casey Meserve is a TecHome Builder Staff Writer, creating investigative and timely articles for its eMagazine and Special Reports. She graduated from Bridgewater State University with a master’s degree in English in 2011. She began her writing career in 2005 as a reporter for Community Newspaper Company and later GateHouse Media. From 2010 to 2013, she worked as an editor at AOL Patch.

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