Embodied carbon in construction materials – the new concern for architects (Podcast)


Production of the currently preferred construction materials for the building industry is one of the largest sources of carbon emissions globally

Key message:

As buildings become increasingly energy efficient in most parts of the world, the production of the construction materials mostly used – concrete, steel and glass – become the buildings’ most severe climate impact. To reduce this climate impact a rethink of the materials that go into construction is necessary.


[00:00:04.140]Aristeidis Tsakiris

Hello and welcome to the podcast series “Scaling Up Energy Efficiency”. This is episode four and today’s topic is “Embodied carbon in construction materials – The new concern for architects”. We’re podcasting from Copenhagen, the city with one of the most efficient district heating network, where it supplies 98 percent of all households with reliable and affordable heating. My name is Aristeidis and I work as a program officer at the Copenhagen Center on Energy Efficiency, a part of the UNEP DTU Partnership. So without further ado, here is your today’s speaker Søren Lütken, senior advisor.

[00:00:48.990]Søren Lütken

Well, hello, everyone, and welcome to this short presentation focused on architecture and the role of architects in climate change. Now, I’m not an architect. I’m going to talk about architecture anyway. So bear with me if I miss the finer details of architecture in in this presentation. Now, first of all, for architects, the good news is they won’t be out of work anytime soon. The global building stock is expected to grow with about 2 billion square meters per year over the next 10 years, from about 162 billion square meters as a current stock to one hundred and eighty three billion square meters in 2026. Now, the bad news is that practically none of that new construction is sustainable. About half the world’s materials, measured by weight, go into buildings. And at the same time, those materials are among the most carbon intensive materials that we have, like cement, steel, tile and glass. Now, picking up on the sustainable development goals that we have been discussing recently or in fact for quite some time now, I know that is not politically correct to prioritize them. There are many different targets and they are all equally important. One thing though, I would like to state here is that if we do not get it right on climate change, we will probably not be able to meet any of the other sustainable development goals. So, of course, my favorite here, and that’s also what I’m going to talk about, is the role of architects specifically relating to climate change. And what I’m going to discuss is based on a working paper that UNEP DTU Partnership published three years ago, in fact, by now, which is looking at city based carbon budgets for buildings and not going to go into detail with the entire publication. But some of its points are the basis for what I’m going to talk about. Now, when we talk about buildings and climate change, the most common consideration of what we mostly think of is all the energy that is going into cooling or heating or operating buildings. And in fact, that’s about 32 percent of global energy production that goes into those three activities related to housing and buildings. We are used to seeing pictures, thermal images of buildings that show where buildings are losing heat or cold in order to improve their performance of the buildings. Now, that is fine. But what we are faced with these years is that the consumption of the buildings, what we in this context would call consumption carbon is in fact decreasing more or less quickly depending on where you are in the world. But it is decreasing simply because there is less carbon in the electricity that comes out of our blocks because we are changing our energy system to be more and more renewable. And it is also decreasing because the efficiency of the buildings is increasing again, depending on where you are in the world. But if you look at, for instance, the Danish building stock, they are becoming very efficient. And the build out of renewable energy means that there’s less and less carbon in electricity here. That in the end you would assume, say by the end of the 2020s, the consumption carbon in the Danish building stock approaches zero, which leaves the scene then to what we call embodied carbon. Now embodied carbon is the carbon that goes into producing the materials that I mentioned in the beginning, the cement, the tile, the steel and the glass and other materials as well. Now, when we see that the consumption carbon approaches zero, this embodied carbon will probably become the next target. So I’m going to talk about Embodied Carbon in the following, that is what our working paper that I mentioned before is about, but I might even go beyond that. Also looking a bit at land and cityscaping, even if I don’t have much background in those areas. Now we used to talk carbon budgets for the planet. We can calculate how much and we are calculating how much emissions the atmosphere can still contain, at least emissions of greenhouse gases. If we want to keep the global temperature rise within a two degree limit, we have also calculated what would be a budget for a country. We have not agreed on any budgets for any countries, even though you can calculate those countries that have agreed to limit their emissions by certain year. You can calculate backwards and see what would be the emission budget for that particular country. We are not familiar with budgets for buildings, and that’s in fact exactly what we are proposing in this working paper. Now I would like to illustrate what it is that we are thinking of because also the embodied and the consumption carbon in fact interact. An example of that is insulation. Now if you put 200 millimeters of insulation in a house, that’s good, particularly if there wasn’t an insulation before, but 400 millimeters isn’t twice as good simply because the insulation effect decreases exponentially. So the thicker it becomes the less you get for the extra 200 millimeters. At some point, those extra 200 mm will consume more energy to produce than they actually save from installing it. That means, of course. Well, you should stop adding insulation materials at that point or probably even before that. And that is exactly the thinking that we are after here. We want designers and architects to consider not only the consumption carbon, but in fact also the embodied carbon when they are designing buildings. And when the authorities equally are setting up standards for for buildings. When you want to reduce the embodied carbon, they’re basically three approaches to do so. First approach would be to increase the material efficiency, and that’s simply to use less material for the same building over the same number of square meters. That is a particular ability of architects. They should be able to consider the usage of materials more efficiently for designing buildings that contain less material for the same amount of square meters. Or in fact, design smaller buildings. That is a bit contrary to what we see many places that there’s more and more square meters per person available, at least that is the case in Denmark might not be the case in Hong Kong, but we have trends that go in the direction of having more square meters per person in many parts of the world. Now, that is one of the first maybe approach to reducing the consumption of materials generally. Second approach is to choose the same materials, but with less embodied carbon. That is not for the architects to do that will be for the developers to do. One ton of steel doesn’t consume the same amount of carbon. Where ever it is produced. So you would prefer buying steel in Norway where the energy is produced from hydro power compared to buying steel in China where most of the energy is produced from coal. So just one example. You would have to look at the origin of the materials to to be able to choose the source of the material with the least embodied carbon involved. And finally, and that is again where the architects really play a significant role is to fully substitute one material with another. What we have been seeing over recent years is a significant focus on replacing concrete and steel with wood construction wood, which in many cases have properties that are, if not comparable then at least is able to replace cement and steel in many applications. We have recently seen the construction of an 18 story building in Norway entirely from wood, and that is in obvious contrast to buildings that we unfortunately siedlecki in Copenhagen in this case where we just had an approval of a new nine story high office building which is announced to be clad with metal when metal cladding. I think where we are now is in fact a thing of the past, we that is a decorative element that definitely should be avoided. Now, focusing on the embodied carbon and the idea that we are presenting in our working paper, which would be to allocate budgets, carbon budgets for construction projects is not just theory. In fact, the European Commission has launched communication on resource efficiency opportunities in the building sector already back in 2014. There is also in that one that reference to a road map to resource efficient Europe all the way back to 2011, which emphasizes the policies need to look at the elemental impact from a lifecycle perspective in order to achieve the resource efficiency goals of the European Union. So it is coming. The question is when? When will it be adopted and how in national legislation. But what we are advocating here is that architects should if they can adopt principles of what I mentioned before, the three principles of reducing the embodied carbon in buildings when they design buildings. So as I mentioned, the budget that we are proposing is a budget for construction that is linked to construction permits. Construction permits are issued by cities, which is why we believe that cities will be the prime driver for bringing down the embodied carbon in the building stock. The idea is simply that when a city issues a building permit, it issues a permit together with a carbon budget, which is set in accordance with calculations of what would be a common usage of carbon in a building like the one which the commission is given for. But that budget over time will be shrinked, just as we’ve seen over the years with the performance of buildings, that the performance requirements for buildings in many cases have been strengthened or the underconsumption has been tightened for buildings in order to achieve an approval. Of course, it’s important to get those budgets right. If you provide too tight budget, construction activity might be hampered. If you provide to LAX an approach, you may not be able to influence the industry because the idea is. There is, in fact, in the end to influence the industry simply by requiring the disclosure of carbon content of the products that go into the buildings and here. Remember that half the world’s materials measured by weight go into buildings. That means if companies are required to disclose the carbon content of that half of the world’s materials, the chance that the rest of the world’s materials are actually also covered is a will being covered is significant. We have seen that, in fact, 20 years ago when or 25 years ago, when the ISO standards were rolled out in Europe, driven by the industry itself, it didn’t take many years before all companies in industry in the value chain simply because it was the demand from larger companies that required smaller companies or sub suppliers to deliver according to a certain standard. That simply influenced the entire value chain so that the entire value chain at some point and it didn’t take long say three, four, five years was able to deliver according to the standard provided. We expect the same thing to potentially happen for construction materials and the disclosure of carbon content. Now, what’s in it for the cities? Well, once you could see cities didn’t really have any interest in this. But if you look at the drive and the momentum behind city networks like C40, you would see that there is a significant self-interest, even political self-interest, in being proactive on climate change. Now, I promised also a few words on city and landscaping because the fact is that cities are heat islands and they capture a lot of heat during the day and they keep the heat simply because the materials that are already carbon intensive materials like cement, steel, glass and tile are excellent heat storage materials as well. So they release the heat during evenings and night. And in fact mean that heat islands like cities with a million inhabitants or more will have average temperatures 1 to 3 degrees above their surroundings. Now what we need to do. To reduce that heat island effect is to cover up those materials that are capturing the heat. That means not only the buildings and the facades. We should definitely not be clad in metal, but in material that is left less heat trapping. But also the streets and the asphalt, the black pitch, which is also capturing heat and releasing that should be covered preferably by trees along the streets or in the parks where we should increasingly avoid what I call designer trees. Once we hear once we there but not wilderness that you would see in other cities like, for instance, New Delhi, where it is forest with a city rather than a city with a few trees, that is important to reduce the heat island effect. And by that, reduce the need for cooling. Now, all these elements are important for architects to consider, and many would say that it influences the architecture of freedom of architects. They are artists. They should be allowed to design what they feel is the right architectural form or the aesthetics that is currently in fashion. But we may be looking for a new architectural aesthetics and it will be one in which the climate change requirements are built in to the designs. The question is, must we then go backwards? With less freedom in our designs, maybe not. Depends on how we look at it. Currently, at least it is a fact that we are exceeding our boundaries and probably we must also accept that there are limits also to architectural freedom. I am advocating that architects take upon themselves the challenge before they are required to do so by regulation or by cities that find that setting carbon budgets for building permits is a way forward.

[00:18:28.940]Aristeidis Tsakiris

Thanks for listening to the podcast “Embodied carbon infrastructure materials – The new concern for architects” with Søren Lütken. If you like, our show share it on your social network. And if you want to know more about today’s topic, check our webpage c2e2.unepdtu.org. Stay tuned and subscribe to receive notifications about our next podcast. See you at the next episode. And do not forget, energy efficiency is a journey, not a destination. Cheers!

City-based Carbon Budgets for Buildings

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Sector: Buildings

Country / Region: Global

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Published by: Copenhagen Centre on Energy Efficiency

Publishing year: 2020

Author: Copenhagen Centre on Energy Efficiency

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