An Easy to Understand Overview of Steep Slope Roofing
California Title 24, Part 6 Building Energy Efficiency Standards were established to reduce California’s energy consumption. Cool roofs are important elements of an energy efficient structure, offering significant energy and cost savings. The California Energy Commission updated the standards effective January 1st, 2023, to revise prescriptive cool roof requirements for all buildings.
Below is a straightforward explanation of the 2022 California energy code1 related specifically to roofing when using Westlake Royal Roofing Solutions’ products. In addition to providing valuable information on how to ensure that your projects meet the new standards, you can be confident that you’re also providing roofs your customers will love for their beauty as well as their energy savings.
The California energy code is divided into different categories depending on the building type, listed in the chart below. Each building type has different requirements to meet specific energy goals. All of Westlake Royal Roofing Solutions’ products are designed for use in Steep-Slope applications so please make sure to reference Steep-Slope2 portions of the code when using Westlake Royal roofing products.
Solar Reflectance, Thermal Emittance and Solar Reflective Index are properties of roofing materials that California specifies to meet certain requirements depending on the building type and climate zone. Solar Reflective Index (SRI) is an easier number to reference as it combines the Solar Reflectance and Thermal Emittance values into a single, easy to use number. Also, as many roofing products have high Thermal Emissivity values, lower reflectivity value products may be able to be used provided they meet the minimum SRI value. The minimum Prescriptive values are listed below.
All values above are minimum values when using the Prescriptive approach, however, products with lower values may be selected when using the Performance approach.
The preferred method for New Build is the Performance Compliance Approach using California Energy Commission approved software. This approach provides flexibility for the builder or designer to select any roofing product, including those with lower than minimum Prescriptive values, provided they are “trading” by implementing other more energy efficient building materials or designs for the building. The input variables for steep-slope roofing are the following:
Aged Solar Reflectance and Thermal Emittance provided by the Cool Roof Rating Council’s (CRRC) Roof Product Listing at www.coolroofs.org. *
Radiant Barrier installed under the roof deck and on interior walls of the attic
Below Roof Deck Insulation
If a product listed on CRRC’s product directory does not have aged values because the product is newly listed, the aged values may be calculated from the initial values using California Energy Commission’s SRI Calculation Worksheet.
Any roofing product not listed in the CRRC’s roof product directory must use the following default values:
Additionally, the code requires all new residential and most new non-residential buildings to have a new solar photovoltaic (PV) system installed. See code for full details.
California Building Climate Zone Map
Many of the code requirements are climate zone (CZ) specific. Check out the map and representative cities to find the climate zones that affect your business.
Detailed city and zip code information are available from the California Energy Commission.
Climate Zones 4 & 8-15, require a Cool Roof to comply with the Prescriptive Approach, the preferred method for reroof projects. Note that Elevated Batten System® battens and high-profiled tiles no longer qualify as energy-efficient alternatives to the Cool Roof requirement. The only remaining alternative options to the Cool Roof requirement are:
R-38 or greater ceiling insulation; or
Radiant barrier in the attic covering the walls and underside of the roof deck;
No ducts in the attic (only allowed for Climate Zones 2, 4, 9, 10, 12, and 14); or
R-2 or greater continuous insulation above or below the roof deck.
Non-residential and Hotels/Motels
Non-Residential buildings, hotels & motels need to meet the same Cool Roof requirements as new builds. No alternative options are allowed for these types of buildings.
What is a Cool Roof?
According to the California energy code, “COOL ROOF is a roofing material with high thermal emittance and high solar reflectance, or low thermal emittance and exceptionally high solar reflectance as specified in Part 6 that reduces heat gain through the roof.”
Footnotes: 1. 2022 BUILDING ENERGY EFFICIENCY STANDARDS FOR RESIDENTIAL AND NONRESIDENTIAL BUILDINGS, TITLE 24, PART 6, AUGUST 2022, CEC-400-2022-010-CMF, California Energy Commission. 2. Steep-Slope is defined as steeper than 2:12 roof slope. Low-Slope is defined as 2:12 or less steep roof slope