Bioeconomy helps to move to a renewable, fossil-free future. The environmental impact is significantly reduced when replacing products made from fossil resources with bio-based alternatives. In a bioeconomy, all products are made from renewable and biogenic resources. In the building sector examples for biogenic sources are traditionally wooden building structures, while green roofs are becoming more popular. The goal of the present project is to assess the amount of biogenic carbon stored in green roofs and wooden buildings overall. The question is if green roofs are improving the biogenic carbon usage of buildings and find out how that can be improved. The methods used are based on construction modelling, life cycle assessment and standardised environmental product declaration (EPD). The results indicate that wooden building structures are not enough for a complete biogenic building to move to a renewable, fossil-free future. Furthermore, the biogenic benefits of green roofs do have a potential, while seen over the whole building the benefits are negligible, since half of the carbon in green roofs material composition is fossil-based. The results are presented as renewable and fossil-based energy as well as biogenic and fossil carbon. These are compared with conventional roofing based on non-renewable standard roofs in Sweden.