Upright or crosswise? Comparative ecological Life Cycle Assessment of a high rise and an elongate apartment building

Urban sprawl is a worldwide tendency leading to an increased demand for adequate highly condensed living space within cities. To meet this demand, there are two typical building types: the high rise and the elongate apartment building. This article aims at providing a comparative ecological life cycle assessment (LCA) for the structure of these two building types. For the analysis, an existing elongate apartment building, planned for a site with bad soil conditions and a high groundwater level in Zurich, was examined. This building was then compared to a hypothetic high rise building, designed for the same site in Zurich and meeting identical energy standards as well as containing a comparable amount of accommodation units and floor space. The weighting of the environmental impact of the buildings over their entire lifecycle was illustrated through two different weighting indices (Eco-Indicator 99 [1], Ecological Scarcity '06 [2]). Additionally, the cumulative energy demand (CED) [3] for both buildings was calculated. Afterwards, a sensitivity analysis was conducted, accounting for the influence of improved soil properties and a low groundwater level. The LCA results show that with bad soil properties, the high rise building has a significantly lower cumulative energy demand and environmental impact than the elongate building, whereas improved soil properties lead to the elongate building exceeding the high rise building in terms of environmental impacts.