May 4th 2023

Navigating the evolving landscape of US Building Energy Codes

Navigating the evolving landscape of US Building Energy Codes

Across the US, a range of building energy codes exist to set minimum requirements for energy efficiency in new and renovated buildings. These codes are developed by organizations such as the International Code Council (ICC) and the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) and are adopted and enforced by state and local governments.

These building energy codes are crucial to reducing the energy consumption of buildings, which account for a significant portion of total energy use across the US. According to the US Department of Energy, buildings consume about 40% of the country's total energy consumption and are responsible for nearly 30% of its carbon emissions.

To address the issue, building energy codes in the US have become increasingly stringent in recent years as policymakers and industry leaders recognize the importance of reducing energy consumption and mitigating their climate impact. The 2021 International Energy Conservation Code (IECC), developed by the ICC, for example, included significant improvements in energy efficiency requirements for new commercial and residential buildings, amounting to a 10.5% increase in energy efficiency over the previous 2018 version. With work already underway on the 2024 IECC update, we can expect these requirements to become even more stringent in the not too distant future.

In addition to the IECC, many states and local jurisdictions have adopted their own building energy codes over the years that exceed the requirements of the national codes. For example, California's Title 24 Energy Standard aims for all new commercial construction, and 50% of commercial retrofits, to achieve net-zero energy by 2030, while other states, such as New York (NYCECC) and Massachusetts (Stretch Code), have also implemented aggressive energy efficiency targets for their buildings.

Of course, this is all before we even consider whether or not a project may also be pursuing additional voluntary green building ratings, such as LEED or Living Building Challenge, or other building certifications, such as WELL, which can add yet another layer of complexity into the process. We are all too familiar with the challenges involved in navigating this complex myriad of codes and rating systems and are always happy to share our insights and advice to help guide our clients through those processes.

Lessons learned in Austin

Recently, our team have been supporting a number of high-profile projects in Austin, Texas, which was one of the first municipalities to introduce its own voluntary green building code (through Austin Energy Green Building) back in 1991, and has since become a national model for many sustainable building practices. AEGB is responsible for development and management of Austin’s energy code and sets specific ratings requirements for energy efficiency, water efficiency, materials, site, indoor environmental quality, community impact and innovation.

Austin energy code compliance can take a few different forms depending on location and project specifics. IECC 2021 is currently the base commercial code reference, and if a project elects or is required to take an AEGB rating path, compliance options using IECC 2021 or ASHRAE 90.1-2019 are provided.   We have assisted projects that pursue the minimum rating level of 1 star, meeting only the AEGB Basic Requirements, and we have also helped projects pursuing points under the E1 voluntary measures credit. The AEGB program overall offers five certification levels (ranking from 1 – 5 stars) awarding points across a range of required and voluntary sustainable measures, with buildings certified at the maximum five stars required to achieve significant above-code predicted energy savings.

Typically, when consulting on code compliance projects, we spend a good amount of our initial time working with the team testing envelope strategies, which follows our recommended envelope or fabric-first approach as this is typically when and where the greatest opportunities lie to optimize passive solar design and reduce the overall building loads. One of the greatest challenges we have found, particularly for many of the Class A commercial buildings we have worked on, is the high proportion of glass and window-to-wall ratio (WWR), which is often commanded in these types of building. While this can obviously have its benefits when it comes to maximizing the availability of natural light, reducing the need for artificial lighting and granting occupants access to surrounding views, it can also be detrimental to a building’s overall energy performance rating, particularly when it comes to warmer climates, such as in Austin. With a high WWR, solar heat gain can lead to unnecessarily high cooling requirements, which can drastically drive up overall energy consumption and equivalent CO2 emissions, while also causing rise to other negative impacts in terms of thermal comfort and glare.

We often support project teams in an advisory capacity, working closely with the architect and engineers to model and simulate the impact that different design decisions and energy conservation measures may have on the overall code compliance or LEED rating, whether they may fall short, and what actions could be taken to help address any apparent deficits. Using dynamic simulation modeling, we can help inform key decisions and navigate the appropriate balance between complying with the relevant code/certification and working towards net-zero energy, while factoring in the client’s wants and needs, to help land on the optimum solutions. While we usually always start with the envelope, we can also provide guidance on strategies to optimize all aspects of a building’s performance, from studying lighting and HVAC system options, understanding mandatory code criteria, right through to impact assessments for different renewable installations.

It is worth noting that there are a few different accepted routes to demonstrating code compliance for many states. Within the IECC (and also under AEGB), ASHRAE 90.1 is an allowed pathway, and from 2016 onward 90.1’s PRM (Performance Rating Method) Appendix G offers an optional compliance route that allows building designers to use dynamic simulation to demonstrate compliance with the energy code requirements. The PRM route is often used for buildings with complex or innovative energy systems, or for projects seeking to exceed the minimum requirements of the code. This is most typically the path which we have find ourselves using in Austin (and to demonstrate compliance with other local and national codes) and can be supported using IESVE software.

ECB (Energy Cost Budget) is another compliance route within ASHRAE 90.1 that uses a simpler calculation method to demonstrate compliance with the energy code requirements. The ECB route sets a limit on the annual energy cost for a building, based on its size and occupancy, and compares this limit to the actual energy cost of the building. However, this more simplistic approach is not always suitable for the complexity of buildings that we are dealing with, particularly in municipalities such as Austin where the local code exceeds national minimum energy code requirements, or an individual project is seeking more ambitious targets/ratings. We do see this utilized at times, however, particularly when a project needs to take a 1-star approach.

While the adoption of more stringent building energy codes in the US is a positive step towards reducing energy consumption and mitigating the impacts of climate change, we understand that it can be challenging to navigate these ever-changing codes and requirements. Within our range of expert consultancy services, we can advise on the range of available routes that can be taken to help your project comply and work towards its desired rating.

If you have a project you wish to discuss, or for further information on how we can help you comply with local energy codes and/or other performance rating certifications, get in touch with our team at