Team Talks feature conversations with Handel Architects employees, exploring their paths into the architecture industry and their unique professional journeys.

Handel Architects sat down for a wide-ranging chat with Louis Koehl, Director of Sustainable Design.

Hi, Louis! Thank you so much for being here with us. Could you tell us a little bit about yourself?

I’m Louis Koehl, an architect. I grew up in Northern Kentucky, right across from Cincinnati—so sometimes I just say I’m from Cincinnati.

I studied architecture at the University of Kentucky. In high school, I loved art but also enjoyed science and math, so I initially considered engineering. But when I visited the University of Kentucky’s architecture program, it was chaotic and fun, and I thought, Let’s see how this works.

I completed the four-year program and earned my Bachelor of Arts in Architecture. It was the early 2000s, an exciting time for architecture with software pushing creative boundaries—crazy renderings, animations, and designs that would never be built. Through one of my professors I got pretty involved in that world and had the opportunity to work on the fabrication-side of some art installations, including one that took me to Vienna.

The connections I made there helped me get to Columbia for grad school, which was an incredible opportunity. It meant moving to New York—a huge change for me. To put it in perspective, the entire population of Kentucky is about 4.5 million, while New York City alone has 8.5 million people. It was quite an adjustment—but I loved it.

That’s when I started thinking more about sustainable architecture and how our designs impact not just the environment but also issues like gentrification and community dynamics. Living in the city and hearing the conversations happening around me exposed me to new perspectives and helped me see the role architecture plays in shaping those discussions.

So you embraced the chaos and the fun. That is a big shift, from Kentucky to New York. What do you enjoy most about New York?

I love how layered everything is—neighborhoods with history piled on top of them. You can see that in the businesses that survive and in the people that have lived there for decades. Then there are all the new people and new generations. I love all the parks and the architecture of the city. I think my favorite thing to do here really is just walk around and kind of meander into spaces you’ve never been. I love that. You can walk into so many places in the public realm and just keep walking. I was really in love with the subway when I first moved here. It is unlike anything that existed where I'm from. There was no public network like that in Kentucky where everyone can just flow in and out and find themselves all over the place on a whim. You're always bouncing from inside your car to inside your home.

Do you have family with you in the city?

I met my wife here 10 years ago. Actually, I was walking to lunch at our old office when I met her. She was going to lunch with a friend of mine that I knew from grad school, and we ran into each other on the street. And that was how we met - a very classic New York meeting.

That is the ultimate rom-com meet cute. And she is a designer as well?

Yeah, she is an interior designer.

So, do you two come home and just talk more design or is design chat not allowed once you’re home?

Ha. Yeah, we do talk about design. Not in any kind of esoteric way. It’s usually about how poorly something was designed at the subway stop or some real-world application.

Can you tell us about your role at Handel Architects?

I've been working at Handel Architects since 2012. I was at a smaller office briefly, but other than that I’ve been here most of my career. Over the course of that time I got increasingly involved in the sustainable design group here. Ultimately, it was getting involved in our Passive House projects like Cornell Tech and Sendero Verde, which I've been involved with for the last 5 years, that pushed me toward building science and high performance. In 2022, I became Handel’s Director of Sustainable Design.

For those unfamiliar with Passive House design, can you explain what it is?

Passive House is a performance-based building certification focused on energy efficiency and occupant comfort. Unlike LEED, which uses checklists, Passive House has strict performance thresholds for energy use, heating and cooling peaks, and airtightness. There’s flexibility in how you meet these targets, making every project a learning process. A key aspect is rigorous verification during construction to ensure the building performs as modeled. It’s deeply rooted in building science, particularly facades and MEP systems, which has greatly informed our practice.

Handel has whiteboard groups—sort of employee-led clubs. The sustainability group has evolved from something ancillary to a core part of the firm. Can you explain that transition?

I took over as facilitator when it was still an informal after-hours group focused on office sustainability, like improving recycling and standardizing details. Over time, our conversations expanded, reflecting broader shifts in how we experienced and addressed climate change. In 2015-2016, it felt like a future issue; now, it's very present.

As sustainability gained prominence in architecture, firms started creating dedicated leadership roles, and we advocated for one at Handel. In 2022, I became Director of Sustainable Design, and I shifted the group from a casual gathering to an active forum for training, education, and project discussions. Now, we focus on how sustainable design and evolving codes impact our work, we learn from each other, distribute information, and touch as many projects as we can. The goal is to ensure sustainability is central to our practice, not just a side interest.

Can you share a project or two that are doing interesting things in sustainability?

One is Sendero Verde in East Harlem, a 709-unit, 100% affordable housing project. It's the world’s largest Passive House multifamily development. It just opened in 2023, and I was involved from the start, carrying it through construction, and it’s been a huge learning experience. Beyond sustainability, the project is also deeply focused on community growth and opportunity, using building technology to support long-term resilience in places like East Harlem.

Another exciting project is an office tower for Santander Bank in Miami, currently under construction. We collaborated with Transsolar, a sustainability consultancy specializing in climate engineering, to explore natural ventilation and human comfort strategies—thinking beyond Passive House efficiency to how people actually experience the building. The 40-story diagrid structure reduces concrete use, cutting embodied carbon. We started with a broad sustainability workshop, testing numerous strategies and refining them as the design evolved. The process has been fascinating, especially understanding how different climates—Miami versus New York—affect sustainability decisions.

What’s the most unexpected or radical sustainability insight from these projects?

The biggest eye-opener has been how much thermostat setpoints impact energy use. Adjusting temperatures by just a few degrees and allowing slight humidity changes can yield huge efficiency gains, sometimes greater than complex sustainability strategies.

On the technical side, we’re integrating building-integrated photovoltaics (BIPV) into the Miami tower’s façade. The exposed slab edges, which provide shading, will be covered with PV panels, blending seamlessly into the structure. If fully implemented, these panels could cover 15% of the building’s energy use—a major achievement for a high-rise. We also explored geothermal solutions, which ultimately weren’t viable due to soil conditions, but the research provided valuable insights for future projects.

Looking ahead, what do you think will shape the future of sustainability in architecture over the next 5 to 10 years?

It may sound like a cop-out, but policy and codes will be the biggest drivers. Advocacy groups, research organizations, and local governments are pushing for energy efficiency and new technologies, but real change happens when these ideas are codified.

We’re already seeing different regulatory approaches: New York’s Local Law 97 penalizes buildings that exceed emissions caps, while Massachusetts is pushing Passive House-level performance for multifamily buildings. The federal government is now working to define net-zero energy buildings, which could lead to more universal standards. Over the next decade, I expect embodied carbon regulations—where buildings have a cap on the carbon emitted during construction—to become more common, much like operational emissions regulations today.

Another major issue is water. We tend to focus on energy, but in places like California and Arizona, water scarcity is already affecting development. Some cities are halting construction due to water supply concerns. Systems for recycling all degrees of wastewater already exist—we just haven’t widely implemented them yet. I think we’ll start to see these systems become standard and even mandated.

What’s interesting is that these shifts might not drastically change how buildings look. It’s less about aesthetics and more about internal efficiencies and behavioral shifts—how we interact with buildings, whether we prioritize natural ventilation despite trade-offs, or how we balance comfort with sustainability. Buildings will still have the same core elements, but they’ll function in smarter, more resource-conscious ways.

On the flip side, where do you feel architects have the most agency in advancing sustainability? Whether from projects you’ve worked on or broader trends, what gets you most excited about where architects can truly push the needle?

If we’re looking strictly at where architects can make the biggest technical impact, I’d say the facade. There’s a huge opportunity to improve efficiency through better detailing, materials, and quality control. Facades play a massive role in a building’s performance, and that is the aspect of the design where architects have the most influence.

But holistically, I think our biggest influence comes from being the primary coordinators of a project. We interact with everyone—the contractor, manufacturers, owners, and consultants—which gives us a unique ability to bring together different perspectives. For example, a Passive House consultant may suggest one detail for thermal performance, while we recognize it might create a constructability issue. Because we see the bigger picture, we are best suited to bridge those gaps.

Sustainable design today isn’t just about solar panels—it’s about the entire life cycle of a building: how it performs, ages, and interacts with its environment. Architects are uniquely positioned to shape this because we’re trained to think across disciplines. Even when our ideas don’t get implemented exactly as we envision, just asking the right questions at the right time can be transformative.

A great example is product availability. Many architects in the Passive House community recall a time when manufacturers told them certain high-performance materials simply didn’t exist. But after enough architects kept asking, those products appeared on the market years later. That collective push—often invisible in the moment—is what drives real change.

That’s really well said. Architects truly orchestrate the process, connecting all the moving parts. It’s incredibly complex, and we’re the ones who bring all the specialists together. Did you always see yourself becoming an expert in sustainable design? Or did your path evolve over time?

I always knew I wanted to be an architect—though funny enough, I first wanted to be a priest as a kid. Not sure where that came from, but architecture quickly followed!

While studying, I never saw myself fitting neatly into the traditional architectural career paths I observed. Some aspects of design I was deeply passionate about, others I struggled to care as much about. Over time, I realized I thrived in a role that allowed me to focus intensely on certain aspects of design while contributing to multiple projects rather than being fully consumed by one or two.

I’m incredibly grateful that Handel supported me in carving out a role that aligns with my strengths and passions. It’s given me the chance to contribute in a way that benefits both my growth and the broader architectural community.

So, to answer your question—no, I didn’t see this exact path for myself, but I also never saw myself following a standard trajectory. It’s been about finding that in-between space where I could make the most impact.

Is there something you particularly appreciate about working at Handel Architects? It could be about your day-to-day work, leadership, or the team—whatever feels most meaningful to you.

I've always appreciated the firm’s structure. There's a balance between efficiency and allowing individuals to shape their projects with their own perspectives. Leadership prioritizes collaboration over top-down decision-making, really engaging principals and senior associates to find the best way forward.

Beyond that, the people here make a huge difference. The leadership—Blake, Gary, and others—genuinely care about what they say they value. Sustainability, for example, isn’t just a talking point; I’ve seen firsthand how much effort goes into making it a core principle of our work. We try to embody our values rather than just stating them, which fosters a culture where younger staff feel empowered to voice their own priorities. That’s a big part of why I’ve worked here for so long—it’s a place where challenges are embraced, ideas are heard, and the work continues to evolve.

That makes sense. For those passionate about sustainability but wary of greenwashing, what advice would you give?

Sustainability isn’t just about checking boxes—like adding solar panels—it’s about finding meaningful ways to make an impact. Every project is an opportunity, even if it’s just asking the right questions in a room where no one else is thinking about sustainability. Maybe you suggest wastewater heat recovery, and while it doesn’t work for that project, now those people will consider it next time.

It’s also about understanding others’ priorities. If someone’s concerned about indoor air quality because their kid has asthma, that’s an opening to connect them to better energy performance or ventilation strategies. Small moments of influence add up.

Lastly, take time to reflect. It’s easy to focus on what’s still wrong, but looking back at progress—how conversations have evolved over a few years—can be motivating. Change happens gradually, but it happens.