MOT ETT MER HÅLLBART BYGGANDE: ÅTERANVÄNDNING AV STOMME

Sammanfattning

Introduction – The construction sector accounts for approximately 40% of globalgreenhouse gas emissions. Building frames contribute with a significant share of theclimate impact of buildings, and by choosing more climate-efficient structural systems,the overall climate impact of buildings can be reduced. This report studies the climatebenefits of reusing structural systems in combination with either timber or steel andconcrete, as well as the opportunities and challenges professionals perceive regardingthese types of structural solutions. Method – The study was conducted as a case study of the renovation and extension ofCampus Borlänge and was divided into a quantitative and a qualitative part. In thequantitative part, document studies were used to collect empirical data, where theclimate database from the Swedish National Board of Housing and environmentalproduct declarations were used to determine the climate impact of different structuralsystems. In the qualitative part, interviews were conducted to study professionalsperspectives on the use of different structural materials and the repurpose of structuralsystems. Results – In the study, the climate impact of four different cases was calculated.Furthermore, it was concluded that timber and reused/repurposed structural systemsinvolve both opportunities and challenges. Reuse, repurpose, and timber all provideclimate benefits. However, reuse and repurpose require more time, analysis, andadaptation. Timber cannot achieve spans as long as those of steel and concrete, is moreexpensive, and professionals often lack experience with the material. Analysis – The analysis shows that, for the studied case, a timber structure combinedwith the reused structure has approximately 80% lower climate impact compared witha repurposed structure combined with a steel and concrete extension. However, arepurposed concrete structure with a steel and concrete extension has approximately58% lower climate impact than an equivalent newly produced concrete structure with asteel and concrete extension. A repurposed concrete frame has approximately 87%lower climate impact than then a newly constructed concrete frame, both with a woodenextension. Discussion – The results of the study are consistent with previous research, althoughcertain differences occur. The findings show that the combination of timber and therepurpose of structural systems is the best alternative from a climate perspective whenit comes to the cases studied. The interviews indicate a demand for a more establishedmarket for reused structural materials in order to make them more accessible forprofessionals to use. The interviews also show that current design practices limit thepossibility of dismantling buildings in the future and that economic factors often aremost important in the choice of structural system.