Assessment of the relevance of “embodied energy” in the building stock of the city of Zurich

The building stock is one of the biggest energy and resource consumers worldwide. Different building stock models have been developed in order to investigate the potentials of energy-efficiency measures and changes in energy supply systems in the building stock. In this context and on behalf of the city of Zurich a life cycle-based building stock model has been designed to assess the greenhouse gas emissions as well as the primary energy reduction potential from the building sector in order to achieve the so-called goals of the “2000 Watt society” by the year 2050. However, building stock models often have important shortcomings since they merely focus on the heating energy demand in the usage phase, neglecting the ”embodied energy” demand of construction materials, building technologies and energy carriers. The goal of the project described in this paper is to provide an estimation of the embodied energy associated to the construction and renovation activities in the building park in the city of Zurich. The embodied energy in Zurich building stock by building new construction and renovation cumulates to 1’796 TJ per year (Reference scenario), 2’270 TJ per year (Efficiency scenario) and 2’304 TJ per year (Eco-efficiency scenario) in 2050. In other words, the embodied energy is roughly 10% of the operating energy and already 190 Watt per capita. The differentiation by construction element reveals interesting findings, for instance the high importance of flat roofs, electrical appliances, heating distribution, air conditioning, sanitation and wall cladding that are often excluded in current environmental assessments