What You Need to Know About Energy Efficient Commercial Roofs in California

If you own commercial property in California, your roofing system needs to meet some of the strictest environmentally-friendly building code standards in the United States. The California Energy Commission (CEC) updates the CALGreen Building Energy Efficiency Standards with additional green requirements every three years. The latest green code has been submitted to the California Building Standards Commission (CBSC) for approval, and if it gets the nod, it will come into effect in January 2023.

Updates could mean that parts of your structure need improving, so it’s a good idea to stay informed so that your property follows the latest building guidelines. To keep you up-to-date with all the new standards and how they might impact your commercial building, read on to learn about energy-efficient roofing and how to stay compliant in California.

Why is Energy Efficiency Important In Commercial Buildings?

While the green building codes and standards may cause some initial setup difficulties for you, sustainable building practices do offer a series of benefits over the long term for commercial buildings, owners, and the California residents who spend their time in them. 

Energy and Cost Savings

With the proper investment in sustainable infrastructure, your entire building can reduce consumption, lower utility bills for direct savings, and decrease overall maintenance fees.  A commercial roof that contributes to annual energy savings can help pay for itself quicker.

Better Thermal Control

Energy-efficient roofing systems – known as ‘Cool Roofs’ – can reflect sunlight and emit trapped heat for better energy transfer. Less solar energy collected with better heat release creates optimal work or storage environments.  

Increased Building Value

Well-designed building components work efficiently together. For example, a high-quality green roof puts less workload on HVAC and indoor air conditioning, leading to a longer lifespan of your building systems. Moreover, consumers see value in energy efficiency, increasing a commercial property’s sales or rental prices. 

CALGreen and Your Commercial Roofing System

CALGreen refers to the California Green Standards building code, Title 24, Part 11 of the California Code of Regulations. The purpose of the code is to enhance public safety and well-being through improved building design. New green buildings can create positive environmental impacts and encourage sustainable construction practices that lead to a better future for all Californians. 

While the code outlines the green requirements for new buildings, it also applies to existing commercial buildings that plan to make additions or alterations. Energy Efficiency is one of five classified green building upgrades listed in CALGreen, so it will extend to roofing systems, even if your structure remained code-compliant in years past. 

The California Building Standards Commission regulates CALGreen (in addition to several other regulatory bodies found on the Matrix Adoption Table). The code applies to new construction, but also anyone with commercial or residential structures such as: 

  • Hotels, motels, lodging houses;
  • Apartment houses, condominiums;
  • One and two-family dwellings, townhouses, factory-built housing;
  • Dormitories, shelters for homeless persons, congregate residences, employee housing;
  • Other types of dwellings with sleeping accommodations (with or without shared toilets or cooking facilities).

If your building qualifies, you may need to meet the new requirements of the California Building Energy Efficiency Standards.

How Can Commercial Roofing Systems Be More Energy Efficient?

CALGreen outlines several different ways that you can update your roofing system for better energy efficiency and to stay compliant:

Section A5.106.11: Reduce Heat Island Effect

Heat islands occur when a city replaces the natural environment. Sunlight and thermal energy often absorb into urban surfaces rather than reflect away, creating additional trapped heat. CALGreen explains several roofing system requirements that can help reflect solar waves and emit heat, leading to optimal energy efficiency. 

Section 110.8: Roofing Products

CALGreen also offers distinct roofing product requirements that can help increase your structure’s energy efficiency. For example, Section 110 explains the appropriate type of insulation you can use, any required roofing membranes, and possible radiant barrier options. 

Roofing product standards adjust depending on the climate zone in which your building resides and the slope of your roof, as outlined inSection 140.3.

3 Ways to Measure Efficiency in Commercial Roof Products

Each of the roofing section standards outlined in CALgreen are concerned with three specific measurements of solar energy and heat transfer:  

  1. Aged Solar Reflectance

Aged Solar Reflectance refers to how well a roof or roofing material can reflect solar energy into the atmosphere. Values are determined over three years because roofing can “soil” over time. The Cool Roof Rating Council outlines the necessary values as β, as shown in the CALgreen codebook:

  1. Thermal Emittance

Thermal emittance refers to how well a roof or roofing material can release trapped heat. The better your roof can allow heat to transfer through, the easier it is to cool your building. Thermal emittance uses a ratio compared against how much heat a black body emits. CALGreen depicts California’s required emittance ratios in the following table:  

  1. Solar Reflectance Index

The Solar Reflectance Index (SRI) is an alternative method for calculating the transfer of solar energy from a roofing material. The index includes other elements such as the roof slope or the type of climate. SRI combines Aged Solar Reflectance and Thermal Emittance values and offers a rank between 0 – 100. See the table below for Calgreen SRI requirements:  

Measuring Energy Efficiency for Roofing Insulation

To have your building meet the insulation requirements of CALGreen, you must also insulate your roof according to two different efficiency standards: 


U-factor refers to the transfer rate of energy through a membrane (such as fiberglass insulation on a metal roof or glass skylights). You would use U-factor values to determine the heat entering or exiting your roof via these membranes. The better your U-factor, the more your building can retain cooled air or release heated air.


While U-Factor represents heat transfer, R-value refers to how well a material can reflect it. R-value is the standard measurement for building materials such as insulation batts, and it shows how well it retains cooled or heated energy. The better the R-value of your roof, the more cooled air remains insulated within your building. The California Code of Regulations, Title 24, Part 12, Chapter 12-13, Standards for Insulating Materials lists the R-Values for individual materials (i.e., Foil, Glass, polyurethane).

Key Takeaway

If you own a residential or commercial property, you may need to update your roofing systems to remain compliant with the CALGreen Green Energy Efficiency standards. While upgrading your structure can feel like a massive undertaking,  it can lead to cost savings, increase the value of your property, and provide far better sustainable building operations over the long term. 

The California Green Building Standards Code 2019 is already in effect, with an updated edition set to pass for 2023. If you are concerned about your own commercial roofing system’s compliance with CALGreen standards, contact RoofSource for an assessment of your roofing system today.

We will give you an unbiased evaluation of your roof’s condition and confirm the services you may or may not need. We will also specify the kinds of materials, quality of the materials, warranties, and building codes you need to use for your particular roofing system, so your commercial roof complies with both CALGreen and Construction Specifications Institute (CSI) standards.