Tetra Tech's Brian Stern Discusses Energy Efficient and Sustainable Building Strategies
Brian Stern is an energy analyst with Glumac, A Tetra Tech Company, who supports firm-wide sustainable and high-performance building design. His work improves building performance from initial concept all the way through operation. Using energy modeling software, he develops holistic building energy efficiency strategies appropriate to local environmental conditions. Brian’s focus spans all market sectors, having experience with the healthcare, commercial, higher education, institutional, residential, hospitality, and manufacturing industries. He is a graduate of the University of California, Los Angeles, with a Bachelors of Science in Mechanical Engineering.
What is the sustainability story of the Wilshire Grand in downtown Los Angeles?
The Wilshire Grand is really a holistically sustainable building. I think being such an impactful building on the Los Angeles skyline, the owners and AC Martin—the architect—wanted to make sure that the building had a strong, sustainability story and was really high performance.
We spent a lot of time during design making sure we could reduce the building’s impact on the environment, and the environment’s impact on the building. As Los Angeles’ climate is primarily cooling-driven—with a lot of bright, sunny days—reducing solar loads on the building as much as possible can make a major difference on energy efficiency. We conducted building shading studies to determine solar loads for different sun positions on an average day and worked with AC Martin on optimizing the window-to-wall ratio, which is a reflection of what percentage of the building envelope—or facade—is made up of windows versus the amount made up of other constructed material. We also designed a really high-performance glazing for the curtain wall system.
The building also features a 550,000-gallon thermal energy storage tank that produces chilled water used in building conditioning. This system allows for the production of chilled water more efficiently at night and prepares the building to cool itself without drawing from city infrastructure during peak periods of the day, which helps to reduce the strain and impact on the grid. It also has a strong financial return for the owners, as the energy used to cool the building is greatly reduced.
The building also has a reclaimed water system that collects stormwater and condensate to replenish its cooling towers. Cooling towers use a ton of water—and being in Southern California and in a drought, this was extremely important to reduce the building’s impact.
What is the main energy efficiency and sustainability challenge in the high-rise space?
One is space—there’s a limited amount of it in high-rise buildings, and the space that is available is extremely valuable. Finding room for mechanical equipment, reclaimed water systems, and thermal energy storage tanks can be a real challenge. That’s why we examine passive designs first to mitigate the space needed to house systems and allow for more rentable real estate within the building.
However, the right strategy for one building is not necessarily right for another. Understanding the owner’s goals and the needs of the local environment is crucial. And that changes from project to project. Local environment not only means the weather conditions and natural resources in that area, but also where you’re getting your electricity from. In California, by 2045 all electricity will be carbon neutral. We’re seeing a lot more owners looking at adding more electrification to the buildings to reduce their carbon footprint and control where they pull energy from. Designers have to be adaptive to these changes.
What are the benefits of energy modeling for clients?
It’s a data-driven design approach. It allows owners and design teams to make decisions on a building and have data to back them up. People often make decisions with their gut, but energy modeling allows you to much more concretely answer questions and make decisions that have huge financial impact to the client.
With the technology and the computing power that we have today, we should be making decisions about our built environment based on the best available data. Energy modeling allows you to answer the hard questions: Should you add additional insulation to this building, should you add or have a higher-performance mechanical system, and what are the cost implications of that.
Energy modeling also helps post-occupancy to determine how much energy you should expect your building to use, as well as look at why the building is using more energy than it should. Post-occupancy, it allows the building owner to understand how their building is performing compared to initial expectations and to take corrective actions to reduce energy usage.
What is the future of energy modeling?
Baseline building codes, especially in states like California, are already extremely rigorous. And that baseline will only rise in the future. So looking at how to design a building to be economical and high-performance today and in the future is extremely important. The energy and sustainability industry within the built environment is changing dramatically. For example, we’re seeing a lot more owners trying to have a more active participation in the grid with things like the thermal energy storage system at Wilshire Grand. I think in addition to what has always been seen as a high-performance design—a good envelope, a good mechanical system, good lighting system, and a good plumbing system—building owners are really looking for ways to reduce their impact on the environment and their local communities.
Flexibility is important, and technology is always changing, so we have to make sure that systems we’re installing in the building are adaptable, based on the knowledge that we have now.