"Our vision is to shift the real estate industry from new builds to existing buildings. We firmly believe that building in existing structures will become the new industry standard," says Sarah Dungs, Chairwoman of the Association for Building in Existing Contexts (Verband für Bauen im Bestand e.V.) and Managing Director of the Greyfield Group. During the webinar "Building in Existing Structures: Seizing Opportunities, Overcoming Challenges," she explained where CO₂ emissions originate in the construction industry, how resources can be conserved, and why a new mindset is essential for working with existing buildings.

Die Immobilienbranche trägt eine enorme Verantwortung: Sie ist bundesweit für 47 Prozent der CO₂-Emissionen verantwortlich, verbraucht 517 Millionen Tonnen an Ressourcen pro Jahr und erzeugt 55 Prozent aller Abfallströme. 40 Hektar Boden werden täglich für neue Gebäude oder Straßen versiegelt¹. Diese Zahlen zeigen deutlich, wie dringend ein Umdenken erforderlich ist – hin zu einer nachhaltigen Bauweise, die die begrenzten Ressourcen der Erde berücksichtigt.

The real estate industry bears an enormous responsibility: It accounts for 47 percent of CO₂ emissions nationwide, consumes 517 million tons of resources per year, and generates 55 percent of all waste streams. Every day, 40 hectares of land are sealed for new buildings or roads.¹ These figures clearly illustrate the urgent need for a shift in thinking— towards sustainable construction methods that take the earth's limited resources into account.

The CO₂ budget – a ticking time bomb

The Mercator Research Institute (MCC) illustrates with its CO₂ clock how many tons of CO₂ we still have left. At our current consumption rate and a 2-degree climate target, we have "budget" left for 22 years. With a 1.5-degree climate target, this period is rapidly reduced to four years—this should give us pause and make us realise that we are operating against a ticking time bomb.

A comparison with the COVID-19 pandemic makes the issue more tangible: Back then, we had to take measures to minimize the risk of infection and prevent hospitals from being overwhelmed—"flatten the curve" was the goal. The same applies to the available CO₂ budget: We must use it sparingly now to buy time until we reach CO₂ neutrality—see the CO₂ clock simulation.

The MCC Carbon Clock

Why existing buildings instead of new builds?

But where does CO₂ actually come from in the construction industry? And beyond that: How can we conserve resources, reduce waste, and prevent further land sealing? The renovation and utilization of existing buildings could provide the answer.

In the construction and real estate industry, new builds are often viewed positively because they adhere to high efficiency standards, making their operational phase more sustainable than that of older buildings. Additionally, the energy sources used in new builds produce less CO₂, bringing them closer to carbon neutrality. However, significant amounts of CO₂ are already generated during the construction phase, which must be factored into a building’s overall life cycle assessment. When looking at this phase, new builds emit approximately 800 to 1,000 kilograms of CO₂ per square meter. But CO₂ emissions function like a limited financial budget: when you spend money while shopping, it’s gone. The same principle applies to CO₂—it is not unlimited. Constructing a new building today immediately depletes part of the available CO₂ budget.

When renovating and preserving existing buildings, CO₂ emissions range between just 100 and 200 kilograms per square meter, depending on the measures taken. Even though new buildings are more efficient during their operational phase, 50 to 75 percent of a building's total lifecycle CO₂ emissions occur during construction. This makes one thing clear: utilizing and developing existing buildings is the most sustainable approach—because everything that already exists has already been accounted for in our CO₂ budget.

At first glance, existing buildings may not always seem optimal in terms of operational efficiency, as they add 15–55 kg CO₂ per square meter during their use phase. This means that significant measures and improvements are needed to achieve long-term CO₂ neutrality.

Distribution of emissions in the building cycle

A new mindset for existing buildings

It's not about being against new construction but to advocate for the potential of existing buildings. Of course, new construction is necessary—but it should be reserved for essential social and community needs, such as hospitals, schools, or housing in areas with acute demand. A “business-as-usual” approach is no longer sustainable for our industry. The best results are achieved when we preserve and intelligently develop existing structures. This requires a radical shift in thinking: moving away from the traditional "new-build mindset" and embracing a new approach that places the potential of existing buildings at the center of our efforts.

This is certainly associated with many challenges: low ceiling heights, problematic pollutants, or seemingly unusable spaces, such as in former factories. How can such buildings be reused for modern purposes, such as offices or flats? For years, we have perfected new build – and now we suddenly have to learn how to deal with existing buildings. As Albert Einstein said: "Problems cannot be solved with the same thinking that created them." For years, new build has been "learned," and now we have to "solve" the issues in existing buildings.

The change is inevitable

Many companies have already missed the shift. The construction industry, with 52 per cent, is considered one of the sectors most in need of restructuring, along with the automotive industry (57 per cent)². So how do we manage to shape the transformation of the construction industry together and solve the major challenges? Innovation in our industry doesn’t mean developing the next "iPhone," but preserving existing buildings.

The traditional approach to new builds cannot be directly applied to existing buildings. However, this requires new processes, a willingness to repurpose, innovative tools, and good collaboration.

The construction and real estate industries have the responsibility and the ability to solve the problems of today—for our future generations and our planet. The most sustainable thing we can do is work together on solutions and see existing buildings as an opportunity. Because, at the end of the day, sustainability begins with preserving what we already have.

¹ Federal Environment Agency, Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection, GlobalABC, BBSR 2020, dena 2021; Destatis 2022

² Roland Berger Restructuring Study 2023