Bioeconomy helps to move towards a renewable, fossil-free future. The environmental impact is significantly reduced when replacing fossil-based products 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 was to assess the amount of biogenic carbon stored in green roofs and wooden buildings overall. The question is whether 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 green roofs do add more biogenic carbon to the building than conventional roofs, while seen over the whole building these benefits are negligible. The results are presented as renewable and nonrenewable energy as well as biogenic carbon and greenhouse gas emissions. These are compared with conventional roofing based on non-renewable standard roofs in Sweden.