Retrofit of European Residential Building Stock: a bottom-up methodology to support large scale decisions

Retrofit of European Residential BuildinEurope is leading the decarbonization of the building sector through directives such as the Energy performance of buildings directive (EPBD) (2010/31/EU)[3] and the Energy efficiency directive (2012/27/EU) that support the implementation of efficiency measures to achieve a highly energy-efficient and decarbonized building stock by 2050. As a consequence, Building stock modelling has become an important topic since it represents a tool able to accomplish the targets proposed in a cost-efficient way. However, the research of cost-optimal levels for an entire building stock is a complex task. Indeed, there are still limitations in the nowadays models as: (i)??They are not able to forecast what the minimum number of buildings to produce a reliable model of the stock is, allowing to decrease the computation time. (ii)??They struggle when detailed information about the thermophysical properties of all the buildings of the stock are missing. This research study solves these issues through a multi-stage methodology based on uncertainty and sensitivity analyses carried out via the coupling Energyplus and MATLAB®. In details, the methodology consists of two main stages: the building stock creation and the retrofit of the stock. The first one is carried out through an archetype bottom-up approach able to directly produce a surrogate model of the stock. The second stage investigates the proposed solutions in economic terms, through NPV consideration, and in technological terms studying the indicators PES (reduction of the primary energy), CES (Reduction of the CO2 emissions) and PPS (reductions of the stock’s peak power requirement) in order to achieve two main objectives: •??To quantify the incentives that are necessary to produce an affordable PayBackTime(PBT ). •??To show how the global effect of the applied solution changes by modifying the number of retrofitted buildings In this way, the policymaker is able to define what energy efficiency measure that reaches the optimum between the economic and technological effect is, on which portion of the stock it should be applied, and what will be the incentives required. The methodology exposed is validated by assessing the retrofit of Barcelona’s residential building stock, focusing the attention on all the residential buildings constructed between 60’ and 79’ for a total of 17209 buildings. The result is a surrogate model in which the minimum number of archetypes that ensure an error below the threshold of 3% is equal to 169. Concerning the retrofit moment, the energy solutions proposed regard windows, roof and wall insulation, and system replacement. The results show that for the presented case study the optimal measure is the introduction of a high efficiency heat pump. Indeed, the target set by the EBPD of a decarbonized stock can be reached directly and the incentives required are in the order of 20 million €. g Stock: a methodology to support large scale decisions