Net Zero and the Codes

Zero energy buildings combine energy efficiency and renewable energy generation to consume only as much energy as can be produced on-site through renewable resources over a specified time period. The goal is these buildings contribute less overall GHG to the atmosphere during operations than similar nonnet zero buildings. Codes, standards and policies are critical tools in meeting green goals by raising the bar for energy efficiency and carbon reductions in new construction and existing building projects.

A CRITICAL TOOL

“Codes drive how our buildings are designed and constructed, and can be the impetus for market transformation of important technologies or strategies in high-performance buildings,” says Alea German, engineering manager, Frontier Energy Inc., San Ramon, Calif.

Ryan M. Colker, vice president, innovation, International Code Council (ICC), Washington, D.C., contends buildings account for about 40% of overall energy use and a similar level of GHG emissions.

“Therefore, in order to achieve their goals, community leaders must consider strategies that directly address this, such as the adoption, implementation and enforcement of modern energy codes, which are a highly effective mechanism that translates their goals into actions by providing a framework for building professionals.”

Sean Denniston, senior project manager, New Buildings Institute, Portland, Ore., explains many progressive base and reach codes are beginning to incorporate NZE compliance paths. “The main driver for NZE in codes is a reduction in energy use and carbon emissions. NZE helps accomplish both of these goals since it requires both optimization of energy performance in the building and the provision of renewable energy.”

“Being primarily a volunteer measure, net zero is primary driven by high-performance programs and their cited standards, not so much building codes,” says Bob Zabcik, member and president of Z-tech Consulting LLC, a Houston-based engineering firm, and acting technical director of the Metal Construction Association (MCA). “The drivers continue to be elevation of the built environment to a higher standard of resource management beyond the traditional considerations of time and money. Carbon reduction is a big part of it, but by reducing fossil fuel use, there are other just as important benefits such as cleaner water and air. The last time I checked, we all drink and breathe.”

Jonathan Humble, FAIA, NCRAB, LEED AP BD+C, regional director of construction codes and standards for the American Iron and Steel Institute (AISI), contends there is no clear understanding what constitutes NZE and that unfortunately, the definition is still debated heavily. However, he does believe the focus of NZE is in creating and exporting on-site energy to serve the needs of the buildings, site equipment and systems. “The current national model energy code provisions and utility programs do not take into consideration the impact in regard to the timing of the exportation of the excess energy into the electric grid. This is an important consideration because if a property’s renewable energy sources (e.g., solar PV) are exporting at a time when the utility is at capacity there is no real benefit to the electric grid. Hopefully this will be modified over time where both parties can take full advantage of the technology more effectively.”

For building owners to fully understand the impact of NZE buildings, Humble advises owners hire a private energy consultant for the purpose of executing a computer-based analysis of their proposed design.

CURRENT CODES FOR NET ZERO

What are the most common and current NZE codes? According to Zabcik, “When the International Green Construction Code (IgCC) adopted the technical requirements of ASHRAE 189.1, it became the de-facto standard for NZE in my mind. ASHRAE’s work is broad-based, touching upon so many different disciplines, which allows for great input from industry and results in a higher-quality standard.”

Colker says the IgCC codes can also serve as a stretch code [allowing individual jurisdictions to adopt energy code requirements more stringent than the adopted energy code] for communities that want higher levels of energy performance. Also, “The 2021 International Energy Conservation Code (IECC) includes a zero-energy appendix for both residential and commercial buildings that communities and designers can use to achieve NZE buildings today.”

The residential Appendix RC lays out a path of achieving NZE through a combination of energy performance requirements and on-site renewables. The commercial Appendix CC provides a way to calculate the amount of renewable energy necessary for a code compliant building to achieve NZE with on-site and off-site renewable energy.

“These appendices provide an option for any jurisdiction to incorporate NZE into their energy code and individual jurisdictions have also begun to incorporate this standard into their codes,” Denniston says. “Washington, D.C. has adopted its Appendix Z, which also provides an NZE compliance option for commercial buildings. The Denver Green Code includes NZE as one of its compliance options for both residential and commercial buildings. The MA Energy Zero (E-Z) Code has been added to the Massachusetts Stretch Code.”

Most NZE codes are focused on modeling-based approaches. “The level of integration of the design of most NZE buildings means that, so far, we are only seeing NZE emerge in compliance paths that utilize energy modeling,” Denniston says. “The MA E-Z code is the notable exception. It includes a prescriptive approach that incorporates principles from Passive House into the IECC prescriptive path and integrates renewable energy. Passive House’s efficiency-first approach is a good fit for NZE and work is being done to codify it as a standard.”

While California has not quite achieved a net zero energy code, German says it has taken some important steps toward one. “The current 2019 Title 24, Part 6 code prescriptively requires a PV system be installed on all new low-rise residential buildings sized to offset approximately 50% of total energy. The 2022 energy code, adopted by the California Energy Commission on August 10, will go into effect January 1, 2023, and includes a prescriptive requirement for PV and battery storage systems on certain commercial buildings.”

If it were possible to create prescriptive NZE code compliance options for simple or replicable building designs, Denniston explains that metal buildings would be a prime candidate, as well as homes and some commercial buildings like big-box stores or mini-malls. “To move these types of measures into model codes, they would most likely require an outside party to bring them to the code-development process, which happens every three years, or to local policymakers for evaluation and adoption.” The ICC Board of Directors recently approved a framework to support communities in achieving their energy efficiency and greenhouse gas reduction goals.

“Through the framework, the Board established a new scope and intent for future editions of the IECC that will ensure the code continues to improve,” Colker says. “It will also include provisions communities can utilize to achieve zero-energy buildings today and by 2030. Additionally, the Code Council is developing code-related resources that support additional energy or GHG saving policies including deployment of electric vehicle-charging infrastructure.”

Humble cites ASHRAE Standard 90.1 Energy Standard for Buildings Except Low-Rise Residential Buildings, containing Appendix G, Performance Rating Method, as a performance-based method. “It is limited in the application of a NZE design approach due to the prescriptive regulations within Standard 90.1. To overcome this limitation, ASHRAE recently created a new standards committee to create ASHRAE 228P Standard Method of Evaluating Zero Energy Building Performance. It is anticipated that this document will be completed sometime in the next few years.”

CONSISTENT CODE APPLICATION

Building codes provide a great avenue for the consistent application of NZE strategies across the industry. “Unfortunately, energy codes are not adopted uniformly across the country,” Colker says. “Some jurisdictions may have older codes in place or no energy code at all. Additionally, when NZE provisions are incorporated into the model codes like in the IECC, they may not find their way into an individual community’s requirements until they update their code to the latest edition.”

Zabcik admits that there are NZE challenges that require out-of-the-box thinking to resolve. “Maybe the best example of this is large overhead doors. I’ve seen buildings where these doors prevented passing a whole-building air barrier test and I’ve seen buildings where they were not a significant source of leakage at all. My best advice is to invest the time and money in up-front planning and research with all the professionals and suppliers involved. This is a very fluid situation across the board and will be for a long time. On the regulatory side, the whole building energy efficiency standard landscape is changing. IECC has moved to a continuous maintenance process to be able to adapt quicker to the changing demands. Much of this work will be driven forward at the association level. At MCA, we are constantly communicating with our member and partner associations to keep ahead of this curve. It’s challenging but very exciting and I’m very happy to be a part of it.”