The construction sector is one of the world’s largest CO2 emitters, energy consumers and waste producers. However, since new buildings and the revitalisation of existing buildings are both essential, it is almost impossible to stop construction altogether. However, planners, builders and the construction industry can make building more sustainable and resource-conserving within the meaning of the circular economy. Or they can simply not build new buildings, and instead repurpose or reuse existing buildings or building parts. In this respect, modular construction has a lot to offer.