Life Cycle GHG Emissions from a wooden load bearing alternative for a ZEB office building

A major contributor to global greenhouse gas emissions is the production of concrete and steel for the construction industry IPCC (2007). To combat global warming, innovative solutions are needed in the construction industry to reduce emissions from both energy and material use in buildings. In a previous study the first phase of a GHG emissions analysis for a Norwegian ZEB office concept was presented. The aim of which was to achieve a zero emission balance where operational and material emissions are accounted for ZEB OM. The results from the first phase showed that the load bearing system accounted for a large share of the embodied emissions. In addition, the ZEB OM ambition level was not met, thus emphasizing the need for further work on alternative solutions and material choices. This paper presents the results of a comparative study between this original office concept study and a predominantly wooden alternative loadbearing structure consisting of wood trusses, glue laminated beams and columns. The wooden alternative is comparable since it has been dimensioned to fulfil the same technical requirements for bearing capacity, sound and fire resistance. In addition, the system boundary was extended to include three alternative end-of-life scenarios. It was found that the wooden alternative structure almost halved the emissions compared to the original concrete and steel ZEB office concept model. This trend is the same in the cradle to gate and all three end-of life scenario’s. The analysis clearly shows that emissions from the production process outweigh any emissions from the material’ s end-of-life treatment. This means that the material choice plays a major role in embodied emissions, as well as it being crucial to reduce the required construction material quantity