Predicting energy consumption and savings in the housing stock: A performance gap analysis in the Netherlands

Abstract

Buildings are one of the key target sectors for energy and CO2 reduction. Policy efforts in the past decades have resulted in technical improvements of the dwelling stock, but despite that, the energy consumption in the residential sector has not yet experienced a dramatic reduction necessary to achieve the set targets. In order to reduce the consumption of the dwelling stock, the European Commission implemented The Energy Performance of Buildings Directive (EPBD), which requires the member states to establish certification schemes for existing buildings. The Netherlands implemented energy labelling in 2008 and based the calculation of dwellings theoretical energy performance on a steady state method. Besides the indication of the label category (A++ to G), the certificate consists of the floor area, the type of dwelling and building related energy use (excluding the appliances), expressed in gas, electricity, heat and the total primary energy consumption. Since the theoretical gas and electricity consumption is portrayed on the front page of the Dutch energy label certificate as 'standard energy use of the dwelling' it became widely used as an indication of consumption and even included in policy goals. Since the dwelling quality has been steadily improving, the primary reason for the reduction failure is the increasing demand from the side of the occupants. In response to that, the thesis stresses the occupant behaviour factor as crucial in actual energy consumption, accounting for as much as 50% of the variance in heating consumption. In order to improve existing policies and achieve real reduction, the occupant behaviour and its impacts on actual energy consumption needs to be understood better. This thesis attempts to shine a light onto how well the theoretical consumption predicts the actual energy use and what the causes of discrepancies are, especially with regard to occupant behaviour. Namely, whether the mentioned reduction potential is realized, strongly depends on the actual energy use of the dwellings. Furthermore, the thesis explores what reductions can realistically be achieved by improving the thermal performance of the dwelling stock and whether or not these match the expectations of policy makers. The research used several large datasets, about dwellings theoretical energy performance, most of which were related to energy label certificates. All the datasets containing theoretical performance were merged with actual energy data. In addition to that, some were also enriched with socioeconomic and behaviour related data from Statistics Netherlands (CBS) or from surveys which were designed for the purpose of this research. Simple descriptive statistics were used to compare average theoretical and actual consumptions. Advanced statistical tests were used for detecting correlations, followed by several regression analyses. In a separate scenario study, the resulting averages of both theoretical and actual consumptions were extrapolated nation-wide in order to be compared with the existing policy targets. Due to low predictive power of the variables in regression analyses, a sensitivity analysis of the theoretical gas use was performed on six assumptions made in the theoretical calculation to show how an increment in one of the assumptions affects the final theoretical gas consumption and whether this can explain the performance gap. Last but not least, longitudinal data of the social housing dwelling stock between 2010 and 2013 was analysed, focusing on dwellings that had undergone renovation. The goal was to find out whether the theoretical reduction of consumption materialised and to what extent. A comparison of the actual reduction of different renovation measures was made in order to show what renovation practices lower the consumptions most effectively.