A low-carbon home is built on data
Green transition 1 February 2022 Søren Brøndum Lars Ostenfeld Riemann
The global construction sector is in an unprecedented growth spurt with a boom in carbon emissions that puts global climate targets at risk. Accurate carbon data on building materials used could put the sector on a greener path.
The total number of buildings in the world is expected to double over the next 40 years, according to the United Nations, jumping from 235 billion square meters floor space in 2016, to 465bn square meters in 2060.
This massive building spree has experts worried. According to the IPCC, we can only emit 400 gigatonnes more CO2 before exceeding the carbon budget for 1.5C. With current building practices, the construction of new buildings will take up roughly 1/3 of this budget by 2060 – 118 gigatonnes of CO2 – in embodied carbon alone.
One key part of the solution, industry experts say, is more reliable emissions data for our construction materials:
“We’ll see more demands to document the carbon impact of buildings in the coming years, which starts with getting more accurate data from building materials manufacturers,” says Søren Brøndum, Managing Director of Buildings, at Ramboll.
“As a start, we have to look at the building materials with the largest CO2 impact. Even on a very large project with thousands of materials, it’s only perhaps 50 materials – cement, steel, and glass for instance – that account for 90-95% of a project’s total carbon impact.”
But without accurate data, designers rely on generic carbon estimates. This could slow the transformation, even as a recent Ramboll report, written on behalf of three industry organisations (in Danish), showed that using best-in-class materials could reduce the embedded carbon of new builds by up to 30%.
Don’t judge a brick by its cover
When planning new buildings, architects and designers look at how much carbon is emitted in the production of various materials – from bricks, to cement and steel frames.
However, this data is often generic, meaning the carbon cost is an estimate from an online database such as the German Ökobau.
In practice, the carbon cost of a brick, for instance, can vary dramatically depending on the producer, type of raw materials used, mode of transportation, and whether it is produced using fossil fuels or renewable energy.
There is a demand for more data in the form of EPDs, but we also need novel materials with a lower CO2-impact like cross-laminated timber. Data isn’t enough, we also need to be more innovative in the materials we use
Søren Brøndum, Managing Director of Buildings, Ramboll
A better option is to choose materials where the exact carbon impact is calculated in an Environmental Product Declaration (EPD). Each EPD costs €7,000-10,000, and this cost has remained a barrier. This could quickly change with new financial incentives for manufacturers.
“Manufacturers who can document their products are more sustainable have a steep competitive advantage,” says Lars Riemann, Executive Director for Buildings in Ramboll.
“Let’s say you have a factory in Poland running on coal power and a factory in Norway using hydropower. They both produce rebars [ed. steel rods used to reinforce concrete], but the emissions from the Polish factory are twice that of their Norwegian competitors. If the price is otherwise comparable, the Norwegian producer has a much stronger position,” he explains.
Policies putting a cap on embodied carbon
This trend is spurred on by new regulations to rein in emissions in the buildings industry.
The Danish Government recently passed legislation putting a hard cap on the embodied carbon of new builds, and other European countries have taken similar steps. The European Union is also considering legislation to make carbon tracking mandatory.
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The construction material pyramid shows the relative carbon footprint of different building materials, using EDPs from Scandinavia. Some building materials such as cross-laminated timber have a negative footprint because carbon is sequestered as the trees grow. An interactive version is available online at https://materialepyramiden.dk/. (Source: The Royal Danish Academy)
“From the moment the new building codes take effect, all designers will have to work within a carbon budget and track the carbon footprint of materials. Initially, it might not be too difficult to stay within the budget, but as the cap is continuously lowered, designers will be incentivised to use low-carbon materials,” Lars Riemann, explains.
The circular economy is the next frontier
The data-backed buildings trend is expected to take hold and spread globally, especially as sustainability-focused regulations such as the EU Taxonomy become a major driver in the industry.
“The next big agendas are likely to be resource management, circular economy, and recycling,” Søren Brøndum explains. “Under the new EU Taxonomy, new builds must include 30% recycled materials in order to qualify as contributing to the EU’s green transition, and that pushes the industry further towards documenting the carbon impact.”
“There is a demand for more data in the form of EPDs, but we also need novel materials with a lower CO2-impact like cross-laminated timber. Data isn’t enough, we also need to be more innovative in the materials we use,” Søren Brøndum says.
To contact the editor of this article, please email Anders Brønd Christensen.
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