Decarbonizing Buildings: An Interview with Stephanie Carlisle

This fall, the Urban Design Forum is launching Cooperative Works, an initiative exploring how New York City can advance economic justice in its coronavirus recovery. In partnership with Deputy Mayor for Strategic Policy Initiatives J. Phillip Thompson and the Mayor’s Office of M/WBE, our Fellows will conduct research on how to create economic opportunity for MWBEs and employee-owned businesses through climate investment, leveraging the new market for building energy retrofits created by Local Law 97.
Leading up to the program, we are pleased to publish a series of interviews with leaders in sustainability in the built environment, inclusive economic development, and racial justice. In our interview with Stephanie Carlisle, Senior Researcher at the Carbon Leadership Forum and former Principal at KieranTimberlake, we discuss the role of embodied carbon in achieving climate goals, how to make high-performance buildings the standard for all projects, and how to showcase the importance of retrofits.


Daniel McPhee: Often, as architects and developers, we aren’t necessarily concentrating our climate solutions on the specific neighborhoods that had been most heavily impacted by the climate crisis. What can be done through design, policy and other strategies to ensure that the benefits of reducing carbon emissions are not just limited to business districts and wealthy neighborhoods where there are clients that can afford it?

Stephanie Carlisle: Climate work and equity work need to be part of a general standard of care. It’s not an add-on service. It shouldn’t be above and beyond. The economics of how architects and engineers get compensated for their work is not simple, but doing a high performance building that entails healthy materials and uses less carbon shouldn’t be a special thing for special clients. We don’t treat fire code, health, and safety that way. We don’t say, “I’d put sprinklers in this building if the client paid me to do it.”

We have to keep ourselves accountable, and I believe that firms should be disclosing the performance of their buildings. Not everyone agrees with that.

We also need economic incentives that will make this work possible and not put the burden entirely on the owners of projects. There are highly successful examples that we need to learn from and probably expand. Subsidies for solar installations worked really well before they were largely rescinded. Right now, there are so many projects in which designers are figuring out how to make net-zero buildings and how to dramatically decrease embodied carbon, but finding a way to get that on a project without any policy mechanisms at all is hugely frustrating.

That is another way in which cities need to be involved. We really need to think about the role of code and regulation that would apply to all projects.

When we are advocating for higher performance, that is also technical. Net Zero design is challenging, and it means that design teams will need to do more modeling and analysis to be sure that real performance meets our assumptions. There is a learning curve and a necessary retooling for many practices. Our industry needs to start supporting itself and expanding access to these skills across the entire design community: we need better data and rules of thumb; we need tools that are easy to use and not crazily complicated; we need more case study projects to learn from, so people can adopt strategies and feel confident in them. The first time you try a new thing on a project, it takes additional time and effort. But if we push for decarbonization across the whole industry, within a pretty short period of time, it just becomes the way that design works.

DM: One of the challenges our Fellows will be researching in the fall is how to support the small businesses in this sector with the right tools and knowledge.

SC: I have learned working on projects, and particularly retrofit projects, going into buildings and seeing where improvements can be made, that the people who run those buildings can do incredible things when they have the freedom to manage them in the way they want. Letting that innovation also happen within the workforce, from the ground up and not always coming from an engineering model, is very important.

DM: Much of your work has focused on the importance of embodied carbon. What is the difference between embodied carbon and energy efficiency?

SC: Broadly speaking, there are two ways of talking about the emissions caused by buildings. The first way of measuring emissions is operational carbon, which is all of the emissions associated with operating a building—heating, cooling, running all the building systems. Then there’s embodied carbon, which is the emissions associated with materials, construction processes, and everything that flows in and out of the building over the course of its entire life. That covers everything from the initial extraction and manufacturing of concrete and steel, all the way to what happens to the materials when the building is demolished.

When we put operational and embodied carbon together, we have a total carbon picture. It looks at the building in its entirety and its relationship to the environment.

DM: When you’re talking about the total carbon picture, what’s the proportion between embodied carbon and energy efficiency?

SC: Building operations make up roughly 28% of global CO2 emissions—a staggering amount—and it’s really important that architects and engineers work on them. There are lots of ways that we can address operational carbon: increasing energy efficiency of buildings, widespread electrification, decarbonizing the grid. We have to do that work.

Embodied carbon is an additional 10-30% of global emissions, depending on how you split up industrial sectors and manufacturing. These are emissions that in the past have always been there looming, but we just put them in this one large bucket called “industry”, and designers never took any responsibility. To be more specific, concrete steel, and aluminum alone are probably around 22% of all of the emissions in the US. When you start to add on other common structural materials, like insulation materials, glass, plastics, mechanical equipment, et cetera, that’s around 25% of global emissions. That’s a really high amount.

Every existing climate model shows that if the design community only focuses on operational carbon, even if we turn all our buildings to net zero buildings, we can’t meet our global climate goals. We cannot stave off catastrophic climate change under any scenarios if we don’t address embodied carbon as well. In part, that’s because a lot of carbon enters the atmosphere before anyone ever occupies the building. That’s why we also call embodied carbon “upfront carbon.” These emissions occur precisely in these critical next ten years.

DM: What are some of the key considerations for thinking about decarbonization with existing buildings and retrofit projects?

SC: How we deal with existing buildings is certainly a huge issue for operational carbon, where we are thinking about energy efficiency and buildings. How do we retrofit these buildings and make them perform better? How can we make them be supportive of a cleaner grid? How can they be tools to propel us into a green economy rather than tethering us to outdated fossil gas infrastructure?

“We cannot stave off catastrophic climate change under any scenarios if we don’t address embodied carbon as well.”

We also need to completely rethink our approach to existing buildings for embodied carbon. The tools of carbon analysis tell us what we’ve always known: you create far more emissions when you build an enormous building from scratch rather than make use of an existing building. But the analysis being done now shows that it is no longer a binary. There is wonderful research looking at how much of the building should you keep, and what are the trade offs between energy efficiency and embodied carbon. It an area ripe for innovation and design intelligence.

I hope that the design communities can value not only those super shiny, incredibly well-engineered Net Zero and Passive House buildings that we need to make. We also need case studies of the normal buildings, which are 90% of the architecture that actually makes up the city. We need to invest far more heavily in applying these techniques to public housing, to public schools and daycares, to simple industrial retrofits, to a whole arena of projects that many of us hardly venture into.

DM: I think you’re absolutely right. We don’t even have the infrastructure to celebrate those simple but important projects.

SC: This past spring, I was teaching a new course for architecture students at the University of Pennsylvania Weitzman School of Design about embodied carbon, and we spent a whole week talking about retrofits and material reuse. Two students in my class were like, “That’s the kind of work I used to do before I went to architecture school, and no one here ever talks about it.” We rarely talk about how renovations are important or groundbreaking.

I love doing that work, and I think that we should also value those projects. The way we talk about them, whether we celebrate them, and whether they win awards matters within design culture. And it certainly matters to the person who lives in that building, because eventually, valuing these projects affects policy. It affects whether or not they can get a subsidy or some technical assistance to retrofit their home, which they probably care more about than a fancy award or professional photography.

DM: How do you think tools like Tally, which you developed to integrate Life Cycle Assessment into design work, could change the way that architects practice?

SC: KieranTimberlake started asking questions about the larger environmental impacts of our projects more earnestly about seven or eight years ago. We scratched our heads and asked, “Why are we just talking about operational energy and not carbon? At the end of the day, we are concerned with environmental impacts, and energy is this odd abstraction. Do we want less green energy? No, we want fewer carbon emissions. Can we build a conversation about that? Why are we leaving this whole other aspect of our work – specifying materials – off the table? How do we actually measure environmental impacts?” A few of us who had studied LCA said, “This is the methodology used in other disciplines, let’s see if we can start applying it to our projects.”

What we found, of course, was that using a tool that’s built to study a cell phone or a pair of blue jeans gets very difficult very quickly when you start trying to model an entire building. The methods existed, some of the data existed, but critically, if we were going to embrace whole building life cycle assessment, or embodied carbon calculations on real projects, we needed something that an architect or engineer could actually use. We needed a tool that fit within a design software—for us, that was Revit—and in a collaboration space with our consultants and with our clients.

We spent about four years developing that tool, first just for ourselves as a proof of concept. Then we engaged several development partners to come into the project and dozens of firms provided feedback and helped us improve the software and commercialize Tally so we could make it available to a broader architecture community. We’ve been using it since then, for about seven years now. There are thousands of architects all over North America who use the tool, but also many students.

Tally and other tools that provide Life Cycle Building analysis calculate embodied carbon during the design process. Image credit: KieranTimberlake.

Because it is integrated into the design process, it allows us to have information about embodied impacts directly connected to our design optioning. We don’t have a separate consultant running a model at the end of a project. Our basic premise is that if designers can’t test an option and get real feedback that they can understand, then that strategy probably won’t make its way into the project.

Now, there are a bunch of other new tools coming online. Over the last eight or nine years, a very large community of architecture, engineering, and construction firms have begun engaging in LCA work and looking at the challenge of drawing down embodied carbon. We’re now in this space where we can share models and strategies, and benchmark data. But it’s still quite early, and everyone’s sort of making it up and innovating as they go. Not only do we need this practice to be normalized across the profession, but we also just need to know what works from a climate perspective, what strategies can scale and be used to truly transform construction.

DM: Even just a couple of months ago, it felt like there was tremendous momentum to tackle decarbonization broadly throughout the design and construction industries. But the pandemic upended many industries, including design and construction. Reflecting on the current moment, how do you think decarbonisation efforts are going to be impacted?

SC: The last few months have really brought an acknowledgement that this current moment of the pandemic is indeed a crisis, but a lot of people and communities have been in crisis for a long time. There are many ways that the current economic crisis, public health crisis, and social justice crisis dovetail with the climate crisis. A lot of communities were already in crisis long before the pandemic. There is no returning to normal. We need to talk and reckon with that.

The current pandemic also shows that we can radically transform how we structure the economy, which industries we choose to prop up, and which industries need support. The green stimulus helps us think about how we can specifically shape climate policy that is centered on equity and justice. I’ve always found that public health is one of the strongest allies in making sure that we have those conversations about equity. That’s been the case for a long time in the design community.

While this moment is really daunting, I think it will probably force us to do some hard work.

Stephanie Carlisle’s work investigates the interaction between the natural and constructed environment, including embodied carbon, life cycle assessment (LCA), urban ecology, landscape performance and supply chains and toxicity of building materials. Combining a background in environmental science and architectural design, she builds bridges between research and practice, bringing data-driven analysis and topical research to complex design problems. She is currently Senior Researcher at the Carbon Leadership Forum, where she works on improving the EC3 tool as well as other carbon data initiatives. She most recently was a Principal at KieranTimberlake Architects where she was an environmental researcher in the firm’s interdisciplinary research group. She is also a lecturer at the University of Pennsylvania Stuart Weitzman School of Design and a Co-Editor-In-Chief of Scenario Journal.

Header image credit: Michael Moran/OTTO