Setting baselines of the embodied, operational and whole life carbon emissions of the average Spanish residential building

Abstract

The construction sector, responsible for 37 % of global greenhouse gas emissions and 36 % of global energy consumption, is transitioning towards a low-carbon and low-energy model. Measuring and optimising Operational Energy and related emissions in the use phase of buildings has entered both markets and regulations. However, the Embodied Energy within construction materials and respective maintenance and end-of-life processes is still in the research phase. Moreover, Global Warming Potential baselines per built square metre need to be defined in the construction sector, integrating operational and embodied impacts. This research has the main goal of identifying for the first time the Whole Life Carbon (WLC) emissions of the average Spanish residential buildings of the period 1981–2010, broken down into Embodied Carbon (EC) and Operational Carbon (OC). For this purpose, first, a regular average and homogenised average of existing European baselines was performed; next, the average Spanish residential building has been defined and modelled with a real sample from year 2013, and its emissions calculated as Scenario 0; and finally, five new scenarios have been compared in order to understand variations in WLC and their EC and OC contributions. This research shows for the average multifamily building apartment in Spain, with a mean net floor area of 73.1 m2, a WLC baseline of 1944 kg CO2-eq·m−2, 30.8 % (559 kg CO2-eq·m−2) being EC, and the remaining 69.2 % OC. In Scenarios 1 to 3, the following are identified: a WLC reduction of 26.0 % (9.2 % EC) by using wood window frames, 0.8 % (2.7 % EC) by laying a wood inner floor, and 16.1 % (1.0 % EC) by insulating walls with recycled cork. All three items are calculated together in Scenario 4, giving a 36.9 % WLC reduction (9.5 % EC). Finally, Scenario 5 was modelled upon Scenario 4 materials, complying with the upcoming European Energy Performance of Buildings Directive as if built in 2021, reaching a potential WLC reduction of 63.4 % (2.8 % EC) from the original Scenario 0. These figures support technical and policy trends towards minimising the impacts of buildings. Focusing on decarbonisation, targets of over 60 % appear feasible with existing market solutions. Reductions of >80 % are also derived from other impact categories, such as Ionizing Radiation, Marine Eutrophication, and Water Consumption, while Freshwater Ecotoxicity increases by 15 %. The 18 ReCiPe Midpoint indicators plus Energy Footprint, are reduced by an average of 50.4 %.