Upfront carbon emissions in Slovenian apartment buildings

The upfront embodied carbon emissions of a selected sample of seven multi-apartment buildings are evaluated. Specifically, the focus is to analyse how the car parking infrastructure influences the results. Four parking solutions are studied: a) surface lot parking, b) building-integrated base floor parking, c) underground parking garage and d) detached above-ground parking garage. The buildings from the selected projects can be described as standard energy-efficient buildings. Reinforced concrete elements compose the building structures except for one project, which used a cross-laminated timber structure. The system boundaries of the study include upfront greenhouse gas emissions due to the production stage (A1–A3 modules according to EN 15978). The carbon footprint is described by three global warming potential (GWP) indicators, presenting the total, biogenic and fossil sub-categories (as defined in EN 15804+A2). The functional unit includes the respective projects’ residential buildings and parking infrastructure. The GWP results of the projects are compared via various normalisation bases (per housing unit number, resident and floor area). The results display that parking can significantly influence the project-related upfront carbon emissions. The overall contribution can be small (approximately 4 %) for surface lot parking, whereas it can reach up to 52 % in the case of underground parking garages. The per parking space associated impact of underground parking garages is, on average, 10 times higher than for surface lots, 80 % higher compared to the detached above-ground parking garage and 33 % higher than the building-integrated base floor parking options. The results showcase the complexity of residential building carbon emissions evaluation, showing that selecting a particular parking space solution can overshadow the benefits of low-emission design alternatives. Additionally, methodological dilemmas regarding the inclusion/exclusion of parking facilities in LCA calculations are discussed.