Environmental Impacts & Benefits of Prefabricated Timber Constructions.

Abstract

Population growth and the changing needs of society are reflected in an accelerated rate of construction to fulfill the needs and adapt to new challenges. Added to this, the increasing pressure to reduce our environmental impact has become overwhelming, leading to demands for better coordination between different sectors and an important shift in construction industry behaviour. Wood construction has established itself as an environmentally friendly construction strategy, although its impact can still be significant if is not done properly. New business models have used this material and its potential to develop temporary, flexible buildings with multiple life cycles.

The task of this study is to identify a way to assess the potential environmental impacts and benefits of these temporary prefabricated timber buildings, especially the embodied energy and carbon savings resulting from waste reduction and the improved efficiency of material usage due to multiple life cycles of the modular elements used in temporary school buildings. It aims to develop a LCA methodology to assess this flexibility by integrating the different life cycles of the structure and including different End of Life scenarios, then to identify the differences in the environmental impact between buildings and to find out where the environmental benefits of this specific type of construction lie. The study was conducted in cooperation between the Technical University of Munich, ETH Zürich and the company, ERNE HOLZBAU AG, who provided data on a case study of a prefabricated school building in Wallisellen, serving as the basis of the analysis in this master’s thesis.

An allocation methodology was developed based on the existing Linearly Degressive approach of Allacker et al. (2017), as adapted by Catherine De Wolf et al. (2020) and this was compared to the traditional distributive methodology (50/50). The methodologies were applied in different scenarios, using the case study presented by the company. The potential of the use of bio based materials encouraged the parallel application of the methodology to quantify the contribution of biogenic carbon, calculated by the Guest and Cherubini (2013) calculation method. Results showed a more transparent approach but also the importance of integrating time to get a better understanding of where the impacts are. The case study concludes with the presentation of a robust methodology that needs further work to integrate the importance of refurbishment and regulations and how they affect the environmental impact of construction. To complete this project, the building was also analyzed as a traditional building with 60 years of life span and compared to a multiple life cycle scenario to find out the environmental impact of a flexible building.