Heather Gayle Holdridge, Assoc. AIA
Josh Huskin Heather Gayle Holdridge, Assoc. AIA

For ARCHITECT's September issue, we talked with San Antonio–based architect Heather Gayle Holdridge, Assoc. AIA, about sustainable design. Here, Holdridge—the director of design performance for Lake|Flato Architects—shares her insight.

What does your role entail?
As the firm’s director of design performance, I oversee the firm’s sustainability and building science efforts. I lead a design performance team that includes design technologists and sustainability specialists. We work with all Lake|Flato project teams to establish project-specific goals, then perform any research or analysis that is needed to meet them.

How has the definition of sustainability evolved throughout your career?
Our understanding of sustainability and its role in architecture has advanced significantly. Lake|Flato has deliberately used the term “Design Performance” to describe our team’s efforts and initiatives because they reach beyond sustainability. Design Performance describes the integration of sustainable design with research, innovation, technology, building science, resilience, social equity, and human health and well-being. This broader scope is gaining traction with other design firms and owners as more projects have employed this approach with impressive results.

What role do architects and designers play in ensuring a sustainable future?
Buildings are responsible for more greenhouse gas emissions than any other sector, including transportation and industry. This presents a great challenge to building professionals, but also a great opportunity, as we have the knowledge and skills necessary to reduce the carbon impacts of buildings. Climate change is one of the biggest threats of the 21st century and endangers national security, human health, food supply, natural ecosystems, and global economies. As stewards of this planet, architects and designers need to do our part in reducing global carbon emissions to protect our world for future generations.

The Georgia Tech Krone Engineered Biosystems Building by Lake|Flato Architects with Cooper Carry as architect of record.
Chris Cooper The Georgia Tech Krone Engineered Biosystems Building by Lake|Flato Architects with Cooper Carry as architect of record.

What’s your firm’s approach to sustainability?
Our integrated design approach involves the entire project team—including the owners, the users, the operators, the construction team, the landscape architects, the architects, the engineers, and the community members—in a collaborative way that develops and refines project goals and strategies from the beginning. The process infuses the project with a high-performance ethos and challenges all participants to create the highest performing building possible. This combination of expertise, free sharing of ideas, and a focused, yet flexible, structure allows for innovative thinking and often results in unconventional solutions.

What’s your firm’s biggest obstacle when it comes to sustainability projects?
It is critical for us to track the actual performance of our buildings after they are operational. While most of our clients are eager to continue collaborating post-occupancy, not all have the time or interest in engaging. We have started talking about the importance of post-occupancy evaluations with clients at the beginning of the design process, or even as early as the pursuit phase. We have found this successful, as more clients understand the benefits and want to participate. There is still much more education needed to make post-occupancy evaluation a typical phase in every design project.

What’s an innovation or design solution that you are particularly proud of?
Lake|Flato started post-occupancy evaluation of our finished projects more than a decade ago. It has been an effective way to compare actual performance to design predictions so we can make on-site adjustments and ensure our performance goals are met. We have monitored a variety of commercial and residential projects of multiple scales. The data we have collected validates our intuition, assumption, and analysis efforts, which results in improving measurable performance on both existing and future projects.

Georgia Tech's 7-acre EcoCommons project.
Nick Hubbard Georgia Tech's 7-acre EcoCommons project.

What’s a project by another group or individual that you think is pushing the boundaries of sustainable design?
I first learned about the Georgia Tech EcoCommons project when I started working on the Krone Engineered Biosystems Building on that campus. At that time, Georgia Tech had recently developed a campus landscape master plan that called for the creation of a permanent ribbon of interconnected, ecologically functioning open space in the heart of campus. At the core of this ribbon, a living laboratory and performance landscape called the EcoCommons was envisioned to be a campus stormwater sponge, biodiversity hotspot, carbon sink, and site for respite and academic research. Nelson Byrd Woltz Landscape Architects and Biohabitats led the design of this project and I have been so impressed with the team’s thorough evaluation of native habitats and ecological performance. They are also facilitating the creation of a living laboratory by installing continuous data sensors and field sampling. I love that the EcoCommons supports the research culture of Georgia Tech by serving ecological and scientific purpose and provides research opportunities for students and faculty.

What research are you following right now?
Another design solution that our firm is excited about and has implemented on many projects is mass timber. By using wood, an inherently carbon-sequestering material, as a building’s primary structure, mass timber can greatly minimize the building’s carbon impact. That wood can only sequester carbon, however, if it is from a forest that was responsibly managed. Through our attempts to investigate the wood we’re sourcing, we’ve found that it is difficult to find transparent data about forestry practices. Ecotrust, Carbon Leadership Forum, Climate Smart Wood Group, Sustainable Northwest, and other organizations have been researching the practices of various forests to identify which ones are sustainably managed to promote carbon storage and which ones are employing harmful practices such as clear-cutting. They have already published resources that assist designers in making more informed choices about wood sourcing, and we are following their work so we can continue to leverage their expertise.

What’s the most pressing issue in sustainability right now?
In order to mitigate the built environment’s contributions to climate change, we urgently need to become more educated on carbon and how to design and construct carbon-neutral buildings. Buildings contribute to global warming potential through both operational and embodied carbon. Operational carbon describes the energy used to operate buildings, while embodied carbon describes the energy consumed from building materials during a building’s full life cycle—from extraction to end of life and disposal. Embodied carbon refers to the global warming potential produced from materials and energy used in the construction, maintenance, and disposal of buildings. Unlike the operational carbon that builds up slowly over a building’s lifetime, embodied carbon starts being emitted as soon as a material is extracted and until it is implemented on the site. Because of this, addressing embodied carbon is becoming more urgent because the carbon has been emitted the day the building is completed. Lake|Flato has been focused on addressing both operational and embodied carbon in our projects through passive, active, and renewable systems and approaches.

If you had to recommend one book or text on sustainability or sustainable design, what would it be and why?
Terrapin Bright Green published the “14 Patterns of Biophilic Design” report nearly a decade ago and I still find myself referencing it regularly. Biophilia is central to Lake|Flato’s sustainable design approach, and this publication is a great resource on the science of biophilic design and how it can be applied in architecture in the most effective ways. I highly recommend this publication to both design firms and owners/clients.

When it comes to sustainable design, what’s missing in architecture and design education right now?
While energy modeling and other building performance simulations are not entirely missing from architecture and design education right now, I’d love to see them more widespread. Architects are currently relying on engineers and other consultants to analyze the energy, daylight, and embodied carbon performance of their projects, but can benefit from performing this modeling in-house. This allows feedback to be more immediate and integrates simulation into the design process. I have already observed that analysis tools are being added to more curricula across architecture programs, and I hope to see this trend accelerate.

An abbreviated version of this article first appeared in the September 2023 issue of ARCHITECT.