Identification of cost-optimal levels for energy refurbishment of a residential building stock under different scenarios: application at the urban scale

Abstract

The low replacement rate of existing residential buildings, together with their high share in the final energy consumption, has put energy refurbishment of the current stock in the centre of the agenda. Nevertheless, due to the high up-front investment and long payback period that it usually implies, deep energy retrofitting is not yet widely applied. In this context, the cost-optimal methodology introduced by Directive 2010/31/EU created a framework to identify the energy efficiency measures that would maximize the economic return. However, the analysis of cost-optimality has often been limited to a single building or type of building, which cannot be extrapolated to an existing building stock. In other cases, the limited number of reference buildings hinders the capture of the great heterogeneity of an existing building stock into sufficiently homogeneous building typologies for a reliable extrapolation of the assessment results. To address such a challenge, this research proposes the application of the cost-optimal method on an urban scale, aiming to identify the suitable range of energy performance that is reasonable to promote in different types of buildings, keeping in mind their specific characteristics. The methodology is applied to the residential building stock of the city of Bilbao, northern Spain, through a comprehensive approach that also incorporates deeper interventions pointing at nearly zero-energy building levels. The results aim to support decision-makers in outlining the most suitable energy efficiency policy and determining the priority targets that demand the mobilisation of investment.