As Grids Get Cleaner, Building Materials Become the Real Climate Problem

Concrete alone accounts for around 7-8% of global emissions. So what happens when the real climate problem in buildings is no longer just energy, but the materials themselves?

In this episode of Climate Confident, I’m joined by Alexander Sexsmith, architect and founder of Sexsmith Architects, to unpack what regenerative architecture means when stripped of the fluff. We look at the climate challenge hiding in plain sight across the built environment: embodied carbon, toxic materials, weak resilience, and the fact that standard construction often performs badly when fire, water, and heat hit. If we’re serious about decarbonisation, net zero, and the energy transition, this matters now.

You’ll hear why cleaner grids are changing the climate maths for buildings, and why materials like concrete, petrochemical foams, and conventional drywall deserve a lot more scrutiny. We dig into how fast-grown bio-based materials such as hemp, straw, and cork could cut emissions reduction timelines, improve indoor air quality, and strengthen resilience. And you might be shocked to learn that some of the materials people still dismiss as fringe are already proving themselves on fire performance and commercial-scale construction.

We also get into the harder bit: scale. Cost, code, skills, supply, consumer awareness, and policy all matter. Because climate tech alone won’t fix construction unless markets, standards, and incentives move with it.

🎙️ Listen now to hear how Alexander Sexsmith and Sexsmith Architects are rethinking climate tech, decarbonisation, policy, and resilient design in the race to cut emissions from the built environment.

Sign up to Climate Confident+ for deep dive analysis of the major climate and energy stories of the day.

Transcript

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Alex: 0:04

A lot of people zoom in on concrete and they say that alone as a single material is seven to 8% of all global emissions.

Tom Raftery: 0:15

Seven to 8%. That's a staggering number, and it tells you the real climate story in buildings isn't just about energy. Good morning, good afternoon, or good evening, wherever you are. This is Climate Confident - stories and strategies that cut emissions. Episode 272. I'm your host, Tom Raftery. Today I'm talking to architect Alexander Sexsmith of Sexsmith Architects about why the climate impact of buildings now runs through materials, health and resilience as much as through power use. As grids get cleaner and heat fire and water risks rise, the real question is what we build with and whether those materials can scale. So first I asked Alex to explain how we came to this work and what regenerative agriculture actually means in practise. Hi everyone. Welcome to the Climate Confident Podcast. My name is Tom Raftery and with me on the show today I have my special guest, Alex. Alex, welcome to the podcast. Would you like to introduce yourself?

Alex: 1:25

Sure. Yeah. I appreciate the chance to be on here. I'm calling in this morning from Tucson, Arizona in the Sonoran Desert. I'm an architect based in Arizona, in part because I think of it as a resilience lab for the future. And in 2021 we decided to make a series of moves to Santa Fe, New Mexico, and, and now here to Tucson, Arizona, really to help accelerate the thinking for me on my practice about what it means to build climate resilient, regenerative buildings. and this was precipitated by a kind of intersection of personal and professional issues.

Tom Raftery: 2:02

And when you say regenerative and, the kind of architecture you're in, can you break down what that means for people?

Alex: 2:13

I think the first time I heard the word regenerative in the context of architecture was at a Living Future conference back in 2018. And it was really about buildings that were able to give back to the environments in which they were situated. Normally, I think we think of buildings as consuming a lot of energy. So that's maybe the kind of primary lens first. And one of the examples that's held up that we were able to tour and visit was the Bullit Center in Seattle, which is built by the Bullit Foundation. Dennis Hayes, the founder of Earth Day helped initiate that building. And so there is a canopy of solar panels on the roof. and it's collecting a huge amount of energy for even, what we think of as rainy, cloudy Seattle. So big picture buildings that give back. I think the next piece of the definition that a lot of people will start honing in on is that we're, thinking about buildings that are shifting from doing less harm. Maybe a sustainable building was seen more and more as something that was doing less harm. And a regenerative building is starting to shift to a, a building that's repairing the environment in its giving back. And we're heading towards a place where the thinking a lot of us, this is a cultural, movement within architecture are is towards buildings that really can perform that way.

Tom Raftery: 3:38

And apart from solar panels on the roof, what other kind of tactics or strategies can help buildings be more regenerative?

Alex: 3:49

Right? So further examples say for the Bullit center, treating its own water on site. My dad was an economist, so he always talked about externalities. If we're leaving all these other issues treating water, indoor air quality, the emissions that the building might be giving off you can think about different types of, say, industrial buildings in which emissions are coming out. You're putting that out into the environment and you're not taking care of that as a building. So it was kind of a closed loop system in that sense.

Tom Raftery: 4:23

And why does this matter now, or does it matter now more than it did five or 10 years ago?

Alex: 4:31

So I think it, it matters, we more than ever because we're, we're seeing the effects of climate change writ large across the globe and these stories are being shared in ways that we can't ignore now. I think for, for many years, the architecture 2030 challenge was an industry-wide challenge that was held up for us all to make better and better buildings, and there is a structural engineering challenge in 20 2050. People are looking at longer horizons, but of course the more impact and, and more change that we can affect now, the less severe the, the changes we have to make later are.

Tom Raftery: 5:15

And why, when we're talking about buildings, you still hear people talking about buildings more as an energy problem rather than a materials problem, for example.

Alex: 5:27

So a little bit of context I got LEED certified in 2010. And I was working at a big corporate firm in Los Angeles. They were promoting this as a way for us all to get a little bit more sophisticated in LEED the US Green Building Council. And so that started to accelerate. That was really one inflection point to accelerate my, my understanding about sustainability. And then, 2017, 2018, I had to deal with a water damaged house, black mold. And really this was the, connection between the personal and the professional that I spoke about earlier where I really understood about the, the effects of the materials that we are building with and what had been industry standard default which seemed energy efficient now was no longer good enough for me. And when I started doing the research. The graphs that I was reading, the articles that I was reading, was pointing to embodied carbon as the next real hurdle for us all to start approaching and start to require us to change our thinking about. What had been, become, say, post-war industrial or large scale home building, commercial office building that now people become, became aware of, had to change and, and we've been in that process for years. And so for example, that Bullit center that I mentioned earlier, they built their structure out of mass timber instead of out of steel or concrete, because the thinking is there's less harm in building in that manner. CO2 emissions. And so it's the materiality, and when we start thinking in that direction, then of course it's all the resource systems that go into making a building.

Tom Raftery: 7:18

One of the reasons that I've heard that described as important is that as we head towards 2030, 2040, 2050, and we decarbonise the grids, then the energy usage of a building becomes less and less important. But the concrete that's used to manufacture the building remains an issue. Or the materials that are used can still be significant issues. So, is that the main thinking behind, or are there other reasons that I've missed out on, or talk to me a little about that.

Alex: 7:56

You grasped the main point. I mean, I think a lot of people for better or for worse, zoom in on concrete and they say that alone as a single material is maybe what, seven to 8% of all global emissions. And if you think about where the areas of growth are you know, in the next say 50 years, very likely Africa, very likely Asia, less so, you know, in terms of total built volume in, in US and or in Europe. Because we're looking at renovating buildings more and more. And so if you think all this new construction happening in, in places with growing populations. If it's done in a manner that continues the pattern of CO2 emissions that has been practiced so far, we're way past our tipping points. I forget the statistics. Something like building a New York City every few days or a week in terms of the, total volume of, buildings globally. And so that's, that's the question. Can we imagine a different way of building that aligns to the kind of climate goals that we need to hit to change the course we're on?

Tom Raftery: 9:06

And can we?

Alex: 9:08

I think that's an open question right now. A lot of people I've been, you know, LinkedIn is full of people talking about the death of sustainability, the death of the green movement. Death and rebirth, they're a cycle. So what are the lessons learned? what are the issues that really are at play? And then how do we scale things that are truly impactful. So looking at agricultural waste, rapidly renewable materials, we think about a tree taking 30, 40, 50 years until it's harvested and able to be used as mass timber, but hemp and straw, cork other materials that are able to be produced in a season that's sequestering carbon and is now material that can be used in a building in a much faster cycle.

Tom Raftery: 9:58

Makes sense. And is this mainly a climate issue or is it a health issue as well, or is it a health issue at all?

Alex: 10:05

Well, if you think about the climate emissions, changing the temperature globally, that of course is heat stress. We've heard of you know, in Phoenix, I assume, you know, in Europe we hear about issues especially with the elderly dealing with heat stress. So we could look at it simply from that perspective. If we think about issues about the emissions that are produced from many industrial building materials, or say petrochemical materials especially. So the high performance foams that have been used in industrial construction to reduce energy use also are toxic. And so that's the, that's the kind of dynamic that's at play. So yes, we can decarbonise the grid, we can use more solar panels. We can use more wind. Reduce the total amount of energy use by energy retrofits, then we're putting less, less emissions. And depending on the chemicals that those materials are made out of, less toxicity in the air. I think the real issue about climate versus health is also about the messaging. So a lot of sustainability leaders have been talking, polling, doing research. Does the word sustainability, do we, do we have a building issue or do we have a messaging issue? And if the issue is talking about sustainability and having it land flat, if it doesn't resonate with people, they're not gonna change their behavior.

Tom Raftery: 11:34

Hmm.

Alex: 11:35

But if this is framed in terms of health, you know, indoor air quality, outdoor air quality. Regional urban heat island effect, these different facets of it. Then it starts to shift the framing of the conversation from one to the other. And I think that's the point is can we have a happy human, building and a happy planet all aligned? And I would say we can, but we're in the midst of shifting our palate to be able to create that future.

Tom Raftery: 12:06

And speaking of the materials, you, you, talked about cork and hemp and another one in the mix there that can be used and the, the advantage of them not taking 20, 30 years, you can get them in a single growth season and they sequester carbon. How feasible is it to use some of those materials as opposed to concrete or mass timber in construction?.

Alex: 12:35

I think maybe the most important distinction to start making is materials that can be used for structural purposes and materials that can be used for insulation or exterior envelope purposes. A lot of times people will confuse those two. And so I would say, when we're talking about this, we're talking about a transition. It is true that there are load bearing straw bale buildings. Hard to, hard to imagine if you think about straw in a field that it could hold up a building, but it's true.

Tom Raftery: 13:08

There was a, whole story about straw buildings and wolves I seem to remember, and little piggies

Alex: 13:12

Right. And that's, that's deep in, that's deep in our memories. So it's hard to, to make that shift. But straw bale, was actually developed in the United States. Right now in Europe, it's being perfected as panelised straw systems that can be assembled to larger and larger scale buildings. And I think the question that you're really getting to is what is the potential for the scale of these solutions? And I think yeah. a lot of us whether we have preference for one or the other building material system whether it's rice straw or wheat straw or, other different forms. It's an agricultural waste that's either typically burned or not utilised to its best performance, not storing the carbon that it could potentially store. And these are crops that again, are, two to four months in their own building cycle. And so it is possible there is a Danish firm called Henning Larson that's set the bar for a a new transport facility that just, I think blew the architectural industry away in terms of the scale that they're aiming for. And it's nice because in an American context. When you say straw bale or hempcrete or some other alternative building material system, you are very likely thinking at residential scale and to be able to think at industrial or commercial or institutional scale. Is it's transformative in an American context and it's, I would say even transformative, even in the European context right now as well.

Tom Raftery: 14:51

And it's interesting that you mentioned that a lot of these agricultural byproducts, straw are often burnt rather than anything useful being done with them. But that then has me wondering how fireproof are they for buildings?

Alex: 15:08

That's a great question. That's one that is again coming back to the, the wolf blowing the house down. It's a perception issue for a lot of people because testing has been done. It continues to happen in, in both America and in Europe. That further tests proving different contexts or different assemblies. But straw bale I believe it was last year, proved a two hour fire rating test. For context most American houses, apart from the separation between the garage and the, the residents, there is no fire rating. When we work on hospitals, larger, more complex buildings where we have different uses, we separate by either a one hour or in, you know, more stringent conditions, two hour ratings. It's actually quite rare in many contexts to even have above a one hour rating. And straw, straw proved that I believe it was last year. It may have been two years ago now. Hemp lime construction also proved that in the United States with something called an ASTM test. So standardised form of testing in the US.

Tom Raftery: 16:13

And are there other properties that these materials have that are better than conventional materials?

Alex: 16:20

That's where it starts getting interesting, is we typically talk about thermal performance in, in the US in terms of R value or U value. But there's also other aspects to this and, we talk about this a lot in the, the Southwest, using thermal mass to delay the, the heat swings to be able to balance out and help improve the performance of a building. And then also something called hygrothermal performance. Meaning balancing, balancing the moisture between the inside and the outside of the building or even within the wall cavity of the, the building. And those all go towards comfort, hot, humid environment, quite different than a dry desert climate, right? In terms of the, the temperature and the heat index and the level of comfort.

Tom Raftery: 17:10

That all sounds great in principle, but obviously the real test is what happens when you try and do this in, in actual projects. Does it work in actual projects? Is it at, at any scale? Can it be done?

Alex: 17:23

I think the proof the data is something that everyone, I think last year everyone started talking about collecting data. All the folks in the hemp lime industry or hempcrete world that I was talking to were interested in gathering data. I started seeing that same conversation proliferating in the straw bale world again here in the US context. Because to feel it and have anecdotal experience is one thing, but to have replicable data across different projects, different project types, that's when people become more and more convinced. And so I think we're moving from the land of a pilot project into larger demonstration projects and and then changing the culture of the construction industry and, and the built environment.

Tom Raftery: 18:12

Obviously. None of this is going to happen if the likes of Hempcrete or, any of the other materials are way more expensive than their conventional competitors. So how they compete in terms of price?

Alex: 18:57

Is it the, the purchasing power paradox? I forget the, the PPP to be able to say, we, we need to be able to do this better and cheaper than existing industries to be able to, take over and to transform the market. And I, I think obviously that's a, that's a real challenge because if we think about, say Tesla. We start with the model S and then build, the capacity, and then you're able to deliver a, a model three. Whatever analogy works for you. The the idea is that the economics of scale, of course changes the price at which these systems make the one-off the artisanal. So in hemp lime construction. A lot of these initial projects have actually been done with volunteer labor as a workshop, so there's an educational component. Then also a, completed project at the end. The next step is government support, whether state or local, possibly private foundations supporting pilot projects. There's a well-known project in Pennsylvania called the PA Hemp House. was a university, a nonprofit developer the state of Pennsylvania coming together to be able to support a pilot project. And that enabled more people to see, touch, engage with a, new style of construction and then start to change the perception issue.

Tom Raftery: 20:19

And are there any examples of it being done at any kinda scale?

Alex: 20:23

So one of the projects that I point to in Widnau, Switzerland, so near Zurich former banker turned, climate Entrepreneur built a, multi-story hempcrete building. And there are many examples in France, which is the epicenter for, I would say epicenter for hempcrete. multi-storey multi-story apartment buildings, small institutional buildings. Similarly straw bale. I was ignorant. I was so, so laser focused on hempcrete that it took a Frenchman coming over here and presenting at at a conference for me to see that this is also happening in the world of straw bale building as well. Multi-story. buildings, load bearing, non load bearing. pretty amazing to see what is possible and then kind of come back to earth for a moment and say, this is still niche. it's very very much in the kind of prototypical scale from the larger market.

Tom Raftery: 21:20

And is the barrier to it getting to the larger market? Is it cost? Is it supply? Is it skills? Is it perception? it all of the above?

Alex: 21:31

All of the above. Yeah. So if, if someone says, you know, Alex, how, how best to approach this, I always say at this point absolutely multi-pronged approach. You have to do the education, you have to do the policy development, the code development. You have to raise awareness in the consumer level. I think you know the stories about people becoming more aware. At least Americans, we spend about 90% plus of our time with indoors.

Tom Raftery: 22:01

Hmm.

Alex: 22:01

And that the indoor air is worse than the outdoor air by multiple, you know, five to 10 times. What does that mean for us? How do we, how do we then take action? As a professional, you start to realise you are fluent in so much more information than the average consumer, and that's, that's you know, an opportunity like this to even have a conversation and share. And then also think about the ways in which, consumer marketing gets a message out about a new product and say, let's engage on that level too. But but absolutely it's a multi-pronged approach.

Tom Raftery: 22:38

And what about the likes of resilience then, you know, how, how, should we think about resilience in an era of heat and wildfires and air pollution?

Alex: 22:50

Right. So, last year I was able to join some of the panels in Los Angeles in the aftermath of the fires, to talk a little bit about a changed material pallet or an updated material pallet for rebuilding Los Angeles. This is fire resilience that we're talking about. I prefaced all the conversations with my personal experience was actually with water resilience. That standard construction, drywall, something very commonly used is not resilient. If it gets wet, it has to be torn out. And so some of these different systems hemp lime, other bio composites, there's rice lime, there's agavecrete. different ways. It's a mixture where, the alkaline chemistry is just different from standard construction and it's able to withstand fire and it's able to withstand water. The two main issues that we're dealing with when we're talking about resilience in much better ways than standard construction.

Tom Raftery: 23:52

And I remember having a conversation at one point with someone in the insurance industry, and those were the two things that he said the insurance industry, he, he was talking about residential insurance at this point, but I'm the same for commercial as well. He said fire and water are the two things that they absolutely hate because the damage they can do to a structure are beyond what anything else can do.

Alex: 24:15

and so kind of circling back to the multi-pronged approach piece, we didn't talk about insurance, but that that is one driver, certainly in the aftermath of the fires in Los Angeles as people look at fire risk in Western United States. I've only been able to talk to one forward thinking insurance professional, and she said, Alex, there's simply not enough hempcrete projects or straw bale projects to be able to inform the risk analysis. And so I thought, well, maybe if the, the changes in the current administration, if federal government isn't supporting this, that insurance companies might be interested to support the development of more resilient systems because their reinsurance may no longer back them up in ways that keep their business model going.

Tom Raftery: 25:05

What? do you think would need to change for regenerative architecture to go mainstream?

Alex: 25:10

I think the intersection between regenerative agriculture and regenerative architecture is a really interesting one to me. A lot of times I will talk about farm to table architecture, so maybe regenerative architecture sounds abstract, but if you say farm to table architecture, I think that that resonates a little bit more with people. In the US again, we, are often presented organic food versus non-organic food. There is certified regenerative, organic, there's lots of, different shades of that now. But those were the kind of black and white that was starting to emerge even, you know, a few years ago. On a consumer level that that information starts to permeate. And if people say this is now the threshold that we're trying to overcome in our buildings as well. Can you start to understand that? And can you, start to imagine that new carpet smell and new car smell are, are not good things? Whoever sold that to you, they're not good things. And that the dawning awareness that these, that microplastics all these different facets of what we do in both the built environment but also consumer products is truly having a global effect. I think that that light is starting to come on in most people's head. And then the question is. How can I have the greatest impact and still live the life that I've been living? How many changes do I need to make and how many are feasible for me to make? I, I think many of us are going through that process. Well, I can, compost my food. Because food waste is a real issue as well. I can buy organic. I can start riding my bike at least a few days a week to the farmer's market or around town. There are behavioral shifts there. And I think the pain point versus the inspiration point is what we're, that's the road we're on is how do we inspire people to make changes rather than overeducate them to the point where they say, you know what? I've had enough. I can't, that's outta my wheelhouse or that's beyond my pay grade. I can't, I'm raising kids. I have a family. I,

Tom Raftery: 27:22

Yeah. Yeah. Other priorities? where do you think this space is gonna be in five to 10 years?

Alex: 27:29

I am very curious to see that myself. I think because I, I know how many people are working at these same issues from, you know, sometimes it's the, the folks in the world of software, the building decarbonisation software to be able to prove that this shift from steel to mass timber is going to have this, this much reduction in terms of CO2 emissions. And and then the policy folks that are working hard to, in the US put forth another farm bill, which would support climate smart agriculture or the understanding that, if we continue to go, the stories I've heard, we, maybe we have 60 crops left based on our current agricultural practices. And so he said, well. 60 crops maybe, climate's not gonna be the thing that gets us. It's, it's our, it's our farming practices. To be able to connect all the dots, and for people to say we need to shift cultural practices in ways that start looking more like the way that we used to do things. And that's when I start talking about kind of ancient future technologies or the, combination of innovation and the and the genius of vernacular architecture, say. The way that we did things for many years because it was honed over and over, people learned incrementally, well, I need to have a, a deeper porch on my south facing windows because too much heat was coming in that those were incremental efforts that were learned and practiced and shared. And then we got away from it, not modern architecture. And then the post-war era we got, we got further and further away from it because we had technology which allowed us to have air conditioning in really hot environments. We didn't need to know the, the genius of passive cooling. And now now we're starting to come back to that. And so it's the weaving of all these things. So, know, with, I mean the, the genius of social media, the internet, we can see these messages and the starting to percolate. And when they really weave together and say, we need to learn from the global south. We need to learn from vernacular cultures, traditional cultures, and Southeast Asia, they're scaffolding even on a huge building like the Patronas towers, bamboo scaffolding, not galvanized iron. This is real a real demonstration of a different type of materiality and a cultural practice wound together.

Tom Raftery: 30:19

Yeah. Yep. I've got a, lightning round of questions for you, Alex, if you're up for it. Just short one sentence sentence, answers. So, retrofit old buildings or build new better?

Alex: 30:34

First retrofit. Absolutely Retrofit. Yep.

Tom Raftery: 30:39

There's a lot more old building stock out there, I guess.

Alex: 30:42

Yeah. And we talked the, some of the programs that I'm involved with, I'm a technical advisor on some of these programs. Healthy energy retrofits or decarbonisation retrofits. Lots of different ways of saying retrofit first,

Tom Raftery: 30:55

Next cheap now, or durable for decades?

Alex: 30:58

Durable for decades. Our, you know, we have a, Cultural issue building cheap now and, and the bill is coming due so durable for decades.

Tom Raftery: 31:09

And what building material worries you most?

Alex: 31:14

I would say petrochemical spray foam, those, they're highly toxic and people have the impression that they're doing a job that they really don't end up doing.

Tom Raftery: 31:25

What's most overrated in green building?

Alex: 31:29

Checklists as one of the real challenges that what we're we're trying to do is a holistic level of change to our thinking. And a checklist can be too simplistic sometimes.

Tom Raftery: 31:42

gotcha. What should every home do better?

Alex: 31:46

Support the health of the occupants that live there.

Tom Raftery: 31:50

Perfect. And what climate solution do architects, underrate?

Alex: 31:56

I'll say thermal mass as a solution. People underrate it because modern architecture has been so much about lightness, thinness.

Tom Raftery: 32:06

Okay. And a left field question for you.

Alex: 32:08

Mm-hmm.

Tom Raftery: 32:09

If you could have any person or character, alive or dead, real or fictional a champion for regenerative architecture, who would it be and why?

Alex: 32:22

Hmm. the name that came to mind was Edison. an inventor, a genius someone who radically transformed America might be able to throw his weight behind and change thinking.

Tom Raftery: 32:35

Great. We're coming towards the end of the podcast now, Alex, is there any question that I did not ask that you wish I did, or aspect of this we haven't touched on that you think it's important for people to think about?

Alex: 32:47

We covered health and climate. we talked about resilience, we talked about a little bit about vernacular architecture and maybe we could talk more about that on an, on another podcast. But I think just raising the issue that there are lessons that we as professionals are learning from looking at vernacular architecture. That's an important one to reiterate. And of course, indigenous knowledge. That's another piece we, I don't think we mentioned that, but, that also is wisdom about how to live in right relationship with the planet that we all could learn from. and I look forward to seeing that conversation continue to, to flourish within what regenerative means in, in the future.

Tom Raftery: 33:29

Very good. Alex, if people would like to know more about yourself or any of the things we discuss on the podcast today, where would you have me direct them?

Alex: 33:37

Direct them to my website, Sexsmith Architects, and there's an easy link to my LinkedIn profile. Also Alexander Sexsmith. those are probably the two best ways to connect.

Tom Raftery: 33:49

Perfect. Great. that's been really interesting. Thanks a million for coming on the podcast today.

Alex: 33:54

Thank you very much for having me. I really enjoyed it.

Tom Raftery: 33:57

Okay, we've come to the end of the show. Thanks everyone for listening. If you'd like to know more about the Climate Confident podcast, feel free to drop me an email to tomraftery at outlook. com or message me on LinkedIn or Twitter. If you like the show, please don't forget to click follow on it in your podcast application of choice to get new episodes as soon as they're published. Also, please don't forget to rate and review the podcast. It really does help new people to find the show. Thanks. Catch you all next time.