Building Technology
2013-12-09
INVITATION TO
MASTER THESIS SEMINAR Jonas Lundgren presents his Master Thesis
The Impact of Life Expectancy in LCA of Concrete and Massive Wood Structures A Case Study of Strandparken in Sundbyberg
Time:
Wednesday, December 18, 9.30 - 10.30
Place:
Seminar Room 3021, 2nd floor, Sven Hultins gata 8
Examiner:
Holger Wallbaum
Opponents:
Shea Hagy
WELCOME!
CHALMERS UNIVERSITY OF TECHNOLOGY Department of Civil and Environmental Engineering Division of Building Technology
SE-412 96 Gรถteborg, SWEDEN Visiting address: Sven Hultins gata 8
Telephone: +46-(0)31 772 1000 Fax: +46-(0)31 772 1993
The Impact of Life Expectancy in LCA of Concrete and Massive Wood Structures A Case Study of Strandparken in Sundbyberg Master of Science Thesis in the Master’s Programme Structural Engineering and Building Technology
JONAS LUNDGREN Civil and Environmental Engineering
Division of Building Technology Chalmers University of Technology
ABSTRACT Recently there has been an increase of energy and environmental certifications in the Swedish building sector which has led to the development of more energy-efficient building operation systems. Contradictory to this the greenhouse gas emissions for construction, maintenance, disposal and the other associative building sector stages have increased. The methodology of Life Cycle Assessment with its cradle-to-grave approach can be used to holistically evaluate the environmental load impacts of the entire building process.
The building’s frame structure represents the largest part of material mass and is therefore crucial in the climate impact of the construction sector. Within the last ten years there have been several LCA comparisons between concrete and massive wood frames. These analyses more or less lack a life span perspective of each structural material. Life spans of buildings vary considerably due to climate conditions, lack of construction quality and maintenance continuity. By weighting statistical numbers of average life span of wooden and concrete structures, and analysing the results per operational year, the LCA can provide a more equal comparison of CO₂ emissions throughout the life span of buildings.
An LCA of two newly-raised multi-residential houses in Sundbyberg is performed comparing a CLT (Cross Laminated Timber) structure with a semi-prefabricated concrete system, using same construction requirements for fire, acoustics and insulation. The assessment results including the materials’ life expectancies shows that the carbon emission impact by wood and concrete is approximately the same. By extending the system boundaries to include reforestation the most outstanding reason for building with wooden structures is the great potential of biogenic storage of carbon dioxide. In a complementary sensitivity analysis it is shown that through balanced harvesting and replanting methods it is possible to make the life cycle of wooden buildings close to climate neutral and act as a carbon sink for global warming. It is also concluded that the end usage phase is crucial for both materials where combusted wood could substitute fossil fuels or continue as carbon storage. Concrete on the other hand has a potential through carbonatation of rebinding almost half of its released fossil carbon dioxide at production, but wood as construction material is still a preferable choice for a future decreased climate impact by the building sector.
Keywords: energy-efficient buildings, building life span, Life Cycle Assessment, LCA, cradle-to-grave, life expectancy, CLT, concrete, reforestation, carbon sink, carbonatation