Eat less meat, fly less, don’t use plastic: The changes we need to make to lower global emissions can often be tough sells. But one effective strategy is a win-win. Retrofitting buildings to be more energy efficient could drastically reduce emissions, while also making residents healthier, more comfortable and more financially secure.
“It’s a case where we can have our cake and eat it,” says Diana Ürge-Vorsatz, an environmental scientist and climate expert at Central European University in Vienna and vice-chair of the Intergovernmental Panel on Climate Change.
This is no marginal issue: Buildings and construction account for at least 37 percent of global carbon emissions. Partly, these are operational emissions — keeping the lights on and keeping buildings warm or, increasingly, cool enough for people living and working in them. But as buildings become more energy efficient and their energy sources increasingly renewable, the carbon produced by the materials and construction of the buildings — known as embodied carbon — can make up more than half of their environmental impact.
In 2024, the United States published its first comprehensive federal strategy to reduce emissions from buildings by 90 percent by 2050, while the EU’s goal is to eliminate them entirely by then. It’s doable, says Ürge-Vorsatz, but would require a profound shift in how we approach our built environment.
It’s a delicate balancing act. We need to make our existing buildings as energy efficient as possible, while at the same time minimising the emissions caused by renovations or new construction. Areas ripe for innovation include insulation materials, which are crucial for energy-efficient buildings but make up more than a quarter of a building’s embodied carbon. Biobased insulation materials derived from renewable, natural sources are one of the possible solutions that scientists, including Ürge-Vorsatz, are looking into.
Knowable Magazine spoke with Ürge-Vorsatz about making buildings more sustainable, and about how biobased materials can support the effort. This conversation has been edited for length and clarity.
Why do you focus on buildings and construction? What is their importance in the context of climate change?
As a physicist, I have been focusing on energy efficiency my entire career. But around 2004, I was leading the chapter on buildings for the fourth assessment report of the Intergovernmental Panel on Climate Change, and one of the lead authors kept saying that buildings can reduce energy use by 90 percent. I thought, “Sure, that’s just a bit of advocacy, show us the literature.” But when he pulled out some examples of passive houses — highly energy-efficient houses that use 90 percent less energy for heating and cooling than typical buildings — I was quite shocked.
I visited an example of such a retrofit in Hungary, where they took this very average panel building [the large Soviet-era apartment buildings made of prefabricated concrete panels], which are all over Eastern Europe, and reduced its energy use by 85 percent. Without any rocket science, and the retrofit costs were really not prohibitive.
I talked to one of the residents who said her quality of life completely changed for the better. Yes, it was nice to have lower energy costs. But what touched me most was her saying that she can now clean five times less than she used to. The engineering literature will never consider this an achievement, but this is an industrial area, with lots of dust, which was gone with the filtered ventilation system. It saved so much of her time and effort.
Her allergy was also gone. I started looking into this and the literature is loud and clear. The energy benefits of deep retrofits can be 80 to 90 percent, but the co-benefits are even more impressive — the improvement in air quality through ventilation and air filtration alone impacts things like cardiovascular disease and the spread of respiratory illnesses. People don’t want to believe it because it sounds too good to be true. But it really is that good.
What share of our greenhouse gas emissions and energy use currently comes from buildings?
Buildings, including their construction, are responsible for over a third of greenhouse gas emissions. But even more importantly, in the European Union half of all gross final energy [the energy sent out to consumers] is used for heating and cooling — not powering cars or keeping the lights on. And high-efficiency buildings can eliminate the vast majority of this. So we have not only enormous emissions and energy use from buildings, but also enormous potential to eliminate these without us noticing it — in fact, with us living much better.
Both the EU and the US have ambitious plans for drastically reducing greenhouse gas emissions related to buildings and construction. What, realistically, would need to happen for them to hit these targets?
First, we need to accept that we have enough buildings in the developed world. There are exceptions, of course, but by and large the population is not increasing, and we already have enough per-capita floor space. For any new construction we should have to justify why an existing building cannot be repurposed and retrofitted instead. We also need a way to disincentivise more floor space, to discourage third homes and huge mansions.
Secondly, we have to significantly reform the financing for deep retrofits. We’ll never reach these ambitious climate targets relying on building owners. While these are very profitable investments, it usually takes 20 to 30 years for them to pay back, just based on energy cost. But from a societal perspective, it’s among the most attractive carbon mitigation strategies — because we are killing so many birds with one stone. We are improving energy security. We are making ourselves independent of Russian natural gas. We are helping the social welfare of our residents by reducing their energy costs. It’s really win-win, from a government perspective.
We need serious public financing for it, and the money is there. Currently, over 7 percent of the world’s GDP is used to subsidise fossil fuels. If we just divert part of that to building retrofits, we are achieving so many goals at once.
What exactly do you mean by “deep retrofit”?
There are many different definitions of a deep retrofit. In our paper in the Annual Review of Environment and Resources, we use the term to refer to buildings that save 80-90 percent of the heating- and cooling-related energy. Deep retrofits take a holistic view of the building, increasing its efficiency by improving the building envelope through measures like enhanced insulation and new windows. Special attention is given to remedying thermal bridges and ensuring air tightness. This, combined with a heat recovery ventilation system, can ideally result in a building that does not need additional heating or cooling at all, though this depends on climate and what the building is used for.
Europe and North America have already recognised the importance of energy saving in retrofits, but what we have been doing is incremental: Let’s change a window here, put a little bit of insulation there. My research has shown that this is actually worse than not doing anything, because it prevents the opportunity for a deep retrofit down the line, which would require different windows and insulation.
Realistically, it makes no economic sense to change a window you just changed. That’s why it’s better to either wait until you can do a deep retrofit, or do it step by step but always with the aim of a deep retrofit. You can only reach the big emission and energy savings if you consider the building as a system, and do it holistically.
Your Annual Review paper looks at maximising energy efficiency in the construction sector, and highlights insulation as a factor that can hugely impact the emissions and energy costs of a building. Why is insulation so important?
Insulation materials don’t have a huge carbon footprint, but the total can run high because we are using a lot of them. And some forms of insulation are associated with not only carbon dioxide but also much more potent greenhouse gases, like the HCFCs used in the production of some polystyrene foams. Of course, it’s still better to insulate than not to. But another important aspect is plastic, which is increasing exponentially year by year, and we are just beginning to understand its enormous negative impact on our health and the environment. Insulation materials represent a huge volume of plastics and other artificial materials.
You’re involved in a European project, BIO4EEB, developing biobased insulation materials. What are biobased insulation materials and what benefits do they provide?
Biobased insulation materials are made entirely or partially from renewable biological sources like plants, and while they aren’t necessarily always 100 percent renewable, they aim to minimise the reliance on nonrenewable raw materials like fossil fuels in their production. For example, biobased polyurethane foams are made using bio-polyols derived from vegetable oils, instead of fossil fuels. This way, we eliminate the emissions caused by these quite energy-intensive insulation materials.
Beyond that, they could contribute to capturing and storing carbon dioxide. Biological materials, like trees and plants, capture carbon dioxide as they grow and release it when they rot. If we keep them from this rotting phase for as long as possible, we are keeping that carbon dioxide out of the atmosphere.
The third benefit is less toxicity, such as the impact of mineral-based insulation materials like glass wool on the respiratory system, or the toxic effects of microplastics from petrochemical materials.
Are there any downsides to biobased materials?
The question is whether we have enough. Today there is already a huge demand for biomass, and a big pressure on land. In the case of forestry or agriculture residues, it’s also not sustainable to take all the organic material, because that depletes the carbon stock and humus content of soil.
These are all difficult questions. How much biobased material is available in a sustainable way that could be used for this purpose? All of these more sustainable solutions are smaller-scale, which also makes them a bit more expensive.
Can you share examples of biobased insulators that you find particularly promising or exciting?
One thing we’re looking at is Posidonia, which is a seagrass that washes up on the shore in the Mediterranean. We’re creating different insulation materials from that, like prefabricated insulation panels. I find that very exciting. But again, we have to look at the scale of it, how much we can use without having to produce it, or if we have to produce it, how can we do that in a safe way?
I also think that hemp and straw could be important, because they have traditionally been used in the construction industry. Another one is biobased foams, because the insulation industry uses a lot of foams, which are traditionally petrochemical, nondegradable and toxic.
You and your team at the Central European University in Vienna assess these materials using life cycle assessments. How does this work?
Life cycle assessment means that we are looking at all the environmental impacts, all the way from the mining of the materials to it becoming waste, and every part of the story in between. It’s a very nice concept, but it’s difficult and enormously expensive to run it properly.
We need a streamlined version that focuses on the big items. We know that we’ll be better off if we replace concrete, steel, cement, Styrofoam with biomaterials that are less energy-intensive. Yes, they are very variable in their impact, but I’m not sure it’s always worth spending the time to do very detailed assessments, because we don’t have the time or the money. I hope that as a result of this project we can develop some simplified methods to assess where the big issues are.
This article was originally published on Knowable Magazine.
