California has set big-time goals for energy efficiency. The state’s Energy Efficiency Strategic Plan aims for all new residential construction to be zero-net energy (ZNE) by 2020 and all new commercial construction to be zero-net energy (ZNE) by 2030. That is, commercial buildings constructed after January 1, 2030 must be optimized to consume equal to or less than the amount of energy they produce.
In order to accomplish this, California’s new building codes have adopted stringent energy standards into the Title 24, Part 6 section. The updated 2019 code provides opportunities and challenges for the building community, though many have been left to wonder what this means for the use of windows and doors in new commercial construction and remodeling.
What is Title 24?
Title 24 is the shortened name referring to the 24th title among the California Code of Regulations; more specifically, the California Building Standards Code by Health and Safety Code Section 18902. (You can see why we just call it “Title 24.”) The code is not limited to energy conservation only, though energy efficiency has become a prominent focus of the newest version given the increasingly strict mandates it includes.
Title 24, Part 6 lays out the California Energy Code, which provides energy requirements guidelines for a variety of aspects of a building, including fenestration.
Prescriptive vs. Performance
The end goal of stringent energy codes is simple—to maximize energy efficiency in a building. However, getting to that goal is not always straightforward. So, in order to meet the requirements in Title 24, architects and builders have two main paths to take when designing a structure: the Prescriptive and Performance methods.
These paths are somewhat self-explanatory. The Prescriptive path means the designer will follow specific code requirements prescribed for each component, including windows and doors. The Performance path allows for more leniency in terms of requirements for components, so long as the overall structure performs to a certain level of efficiency.
Requirements can vary by building, depending on whether the project is defined as low-rise residential (1-3 stories), high-rise residential (4 or more stories), or nonresidential.
This chart from the California Energy Commission shows the Prescriptive requirements for fenestration and glazed doors:
These Prescriptive requirements apply to replacement fenestration, as well.
The Prescriptive path is the simpler one, but it’s also the least flexible, as there may be a particular product or component you’re looking to implement in your project that just can’t meet a requirement on its own. That is where the Performance method comes in.
As the U.S. Department of Energy notes in the “Compliance Toolkit” at its online resource center, “A performance-based code provides more design freedom and can lead to innovative design but involves more complex energy simulations and tradeoffs between systems.” These tradeoffs and simulations can be an effective way to reach overall Performance goals, and it is recommended builders and designers work with energy code experts and consultants to ensure they are taking the necessary steps. In order to prove compliance, the minimum level of energy efficiency necessary is calculated through a specialized state-approved software program using a detailed account of the building.
Fortunately for the design and building community, the window and door industry has worked tirelessly to keep up with the ever-evolving world of codes, energy efficiency, and design trends. This allows designers the flexibility to take the path that best suits a particular project and to implement the right windows and doors for their aesthetic and performance needs.
For more information, visit the California Energy Commission website.