Environmental and economic comparison of prefabricated timber construction with straw and earth implementation versus conventional construction methods

Abstract

Prefabricated timber modules, which are insulated with straw and plastered with clay, promise an envi- ronmental advantage, as biogenic material replaces the usual insulation of conventional timber con- struction. This thesis examined the potential of this construction in terms of the environment, but also in terms of its costs. In addition, looking to the future, various possible legislative measures to promote alternative construction and their impact on the construction industry were considered.
In order to analyze the potential of this straw construction method, a typical multi-family house in Swit- zerland was used as a case study, where a comparison was made with concrete construction and con- ventional timber construction. Among other things, a life cycle assessment was carried out to measure the environmental potential. To investigate the dynamics in the construction industry, that could be in- fluenced by future legislative measures to promote green building, a literature review was performed as well as examined through the case study.
Prefabricated timber elements with straw insulation and clay plaster showed a great environmental po- tential in comparison. Not only do they emit significantly less greenhouse gases, almost up to half of concrete construction and a quarter less than conventional timber construction, but they also store a large amount of CO2. However, there is a price difference of up to 30% compared to concrete construc- tion. If legislative measures are to be taken to reduce this price difference in the future, emissions stand- ards, emissions trading, CO2 taxes or subsidies could achieve a promotion of alternative construction methods. At the same time, however, depending on the system, difficulties arise such as their imple- mentation, flexibility, economic stability of the construction industry or geographical expansion. Applying a simple approach of CO2 taxes and subsidies to the case study shows that these can cause a price difference of 15% instead of 30% to concrete construction. However, the greatest potential in the case study would be a subsidy that would grant a higher utilization factor, which could be of great interest to the builder.
The application of straw and clay in this variant shows without doubt great potential for environmentally friendly construction, but this alternative construction method is more expensive and should be sup- ported for more protagonism in construction probably in a mentioned legislative way.