Influence of Methodological Choices on the Environmental Trade-off between Renovation and Reconstruction

Abstract

The environmental trade-off between renovation (i.e. application of energy conservation measures) and reconstruction (i.e. demolition followed by new build) is an emerging topic under study. Although in many studies renovation is preferred over reconstruction from an environmental viewpoint, opposite conclusions can be found as well. The reason behind these ambiguous conclusions is often explained by the difference in energy performance achieved between the renovation and reconstruction scenario. However, the question of to what extent methodological choices influence the trade-off between both scenarios is rarely asked. The environmental impact of a building is commonly examined by means of life cycle assessment (LCA). Despite the fact that several standards with regard to LCAs do exist, there are no specific guidelines when buildings with a different (remaining) service life are compared, or when an existing building is the starting point of the assessment, as the standards are mostly tailored for new buildings. Consequently, different methodological approaches can be found in literature to (1) determine the reference study period and (2) allocate environmental impacts. This paper therefore examines the effect of several approaches in terms of both aspects on the trade-off between renovation and reconstruction. First, existing approaches are gathered from literature after which they are applied to a renovation and reconstruction case study with an identical geometry, energy performance, and HVAC installation. For the environmental evaluation, an LCA is performed following a cradle-to-grave approach. The environmental impact of the operational energy use and HVAC installation is however excluded since it is considered equal for both cases. The results show considerable variations in the trade-off between renovation and reconstruction. Establishing a robust and well-defined methodological LCA framework that allows for a consistent comparison of renovation and reconstruction, is a key challenge to determine how to guide and support the choice between both scenarios.