When it comes to sustainability, reusing something that already exists is usually better than creating something new. The same goes for architecture, a fact that a local Stockholm firm exemplified with its newly unveiled project, which turned a 1990s office building into a series of apartments with a green roof. Dubbed “Vintertullstorget,” the project was able to preserve the existing concrete structure rather than knocking it down and starting from scratch, reducing the need for excessive construction materials and labor.