Guideline for the Use of Straw and Hemp in the Swiss Construction Sector

Abstract

The bio-based materials straw and hemp show a great potential for storing CO2 in the Swiss building stock and thereby reducing the embodied emissions of buildings in Switzerland. The goal of this Master Thesis was to provide a guideline for the use of straw and hemp in the Swiss construction sector. Literature review served as a foundation for the general understanding of the problem, while interviews conducted with various representatives of the Swiss construction industry provided additional expert knowledge as well as insights about the current perception and acceptance of straw and hemp as a construction material. The obtained results show that the availability of straw and hemp is rather limited in Switzerland, yet considering the neighbour countries there is an excessive amount of straw and a decent amount of hemp shives available. Straw bales and hempcrete (bio-composite material con- sisting of hemp shives, lime and water) contain many favorable material properties which go beyond thermal insulation, namely additional thermal mass, decent acous- tic insulation, fire protection, good workability and advantageous disposal options. Depending on the construction size and the client’s needs there exists a wide range of straw bale and hempcrete applications. Prefabrication in combination with a supporting timber frame shows the biggest up-scaling potential for new construc- tions whereas the wrapping technique, in-situ-cast hempcrete and hempcrete bricks are particularly suitable for renovation. However, also other techniques such as load-bearing straw bales or timber stud and frame constructions have its eligibility and can be applied cost-effectively. The main obstacles inhibiting the use of straw and hemp in practice are the missing publicity and the lack of experience. Suitable solutions are the advertisement of the materials’ unique selling points, research, education, workshops and legislation incentives. Implying a certain curiosity and the willingness to work with new materials, straw and hemp are more than ready to complement the Swiss construction market.