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2024
Aimée Michelfelder
und Jurek Brüggen
in collaboration with ammi
The most sustainable building is the one already standing, as it embodies "grey energy"—the energy and resources previously invested in its construction. These materials, already extracted, transported, and assembled, have the smallest ecological footprint. Utilizing existing structures avoids the need for energy-intensive processes like manufacturing and transportation, preserving resources for as long as possible. In contrast, demolition and new construction not only waste this embedded energy but also produce massive amounts of construction debris, which must be managed. Even energy-efficient new buildings, when constructed with ecologically sound materials, incur significant "grey emissions" due to material production, transportation, and assembly. These emissions often equal the operational emissions of a building over 50 years. Consequently, refurbishments tend to have a much smaller environmental impact than new constructions, particularly when designed with sustainability in mind.
Post-war buildings from the 1950s to 1970s represent a substantial opportunity for climate-friendly transformation. These structures, which constitute about 40% of Germany's building stock, are typically energy-inefficient yet relatively simple to upgrade into nearly zero-energy buildings.
Beyond climate concerns, the construction sector also accelerates biodiversity loss, which is an equally dire threat to humanity. Extracting raw materials, building infrastructure, and sealing off land for development obliterate natural ecosystems, depriving countless species of their habitats. Germany loses 160 square kilometers of land to sealing every year—a scale equivalent to the city of Potsdam. These areas, once biodiverse, are turned into barren spaces that undermine ecological resilience.
This issue is exacerbated by the prevalence of detached single-family homes. With around 16 million such houses in Germany, many occupied by only one or two people, these low-density developments consume disproportionate amounts of land and resources while fostering urban sprawl. The result is further habitat destruction, higher traffic volumes, and inefficient energy usage.
To address these challenges, we must prioritize refurbishments over new builds, embrace higher-density housing models, and design urban spaces that coexist with nature. By maximizing the utility of existing structures and limiting new land development, we can reduce emissions, waste, and resource consumption while preserving biodiversity. Architecture has the potential to shape a sustainable future, but only if it focuses on adaptive reuse, efficient space utilization, and integration with natural ecosystems. The choices made today will determine whether the built environment becomes a solution or continues to contribute to the planet's growing ecological crises.