The use of green roofs to improve wooden buildings for a future bioeconomy

¹ RISE, Research Institute of Sweden, Division of Built Environment, Department of System Transition and Service Innovation, Unit of Energy and Environmental Systems Analysis, 41258 Gothenburg, Sweden.
² RISE, Research Institute of Sweden, Division of Built Environment, Department of Building and Real Estate, Unit of Building Envelope and Building Physics, 50115 Borås, Sweden.
³ LTU, Luleå University of Technology, Division of Industrialized and Sustainable Construction, Department of Civil, Environnemental and Natural Ressources Engineering, 97187 Luleå, Sweden.

^* Corresponding author: birgit.brunklaus@ri.se

Abstract

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.