Household budget restrictions as reason for staged retrofits: A case study in Spain

Staged retrofits were introduced in the energy performance of buildings directive, but they remain underexplored in the literature. This paper addresses households' budget restrictions as a reason for implementing staged retrofits based on a data-driven analysis of owner-occupied single-family houses in Spain. The research question is as follows: What is the impact of households' budget restrictions on modelling the optimal timing of staged retrofits and their resulting CO2 emissions? This study combines two methods: the statistical matching of European Union statistics on income and living conditions and household budget survey data and the staged retrofit mixed-integer linear optimisation model. This paper concludes that without any financial measure designed to accelerate building stock decarbonisation, a building renovation roadmap, from the first optimisation year until the last measure, may consume a total of 17 years. Various energy policy instruments addressing building stock's techno-socioeconomic heterogeneities, such as innovative financing and incentive schemes, are needed to reduce the CO2 emissions of buildings significantly and rapidly. Furthermore, the use of metrics representing CO2 emissions with time (e.g. cumulative CO2 emissions) is recommended for building renovation passports. Such a metric will enable the monitoring of buildings' decarbonisation and better frame EU Member States' policy strategies.