A comparative study of embodied and operational environmental impact of a multifamily building with different framework materials

Abstract: The different life cycle phases of a building account for different amounts of environmental impact. During the past years the operational energy use in the building and construction sector has been reduced whilst relative and absolute embodied impact has increased. To reduce the overall environmental impact, design and material choices have to be optimized in relation to the energy use. The performed study aims to enhance more environmentally conscious decision-making in the building and construction sector by increasing awareness and knowledge about the environmental impact from life cycle phases of a building as well as different framework materials.  Three different designs of a typical Swedish multifamily building have been analyzed in the study. The case building has a concrete frame. The two alternative designs are based on the case building but has lower energy use. In addition, one of the alternative designs has a cross laminated timber frame. They were all analyzed in terms of embodied and operational environmental impact, expressed as carbon dioxide equivalents per heated area. A simulation model of the case building, calibrated with measured data, was implemented to calculate the operational energy use of the designs. The embodied emissions were calculated for the enclosing and load bearing structures.   The results show that both alternative designs have lower environmental impact than the original state of the case building. The construction with wooden frame has approximately 30 % less embodied emissions compared to the original state. Concrete has the largest share of the total embodied emissions and choosing product specific concrete can yield a reduction in embodied emissions of more than 9 %. Sensitivity analysis of the operational energy show a significant difference in the results depending on approach and system boundaries. A future scenario of operational energy result in increased relative contribution of embodied environmental impact.