Resumen de Performance gap in energy retrofitting of social housing: comparison of two case studies in Southern Europe
Inés Díaz Regodón, Andrea Sangalli, Javier Llorente
Efficient urban renovation and efficient energy retrofitting have become a priority for many municipal administrations in order to achieve the ambitious energy and environmental objectives set by the European Union. But for a real accomplishment, it is necessary to evaluate the effectiveness of the strategies that facilitate the transformation of existing buildings towards nearly zero energy buildings. In the context of EU-GUGLE project, a European six year (2013-2019) collaborative project within the 7th Framework program, over 150.000 m2 of residential buildings were retrofitted, with a total investment of more than 80M€, demonstrating different sustainable energy technologies and techniques implemented in 36 lighthouse buildings, and set of buildings, located in Austria, Finland, Germany, Italy, Slovakia and Spain. In Sestao (Spain) a deep urban renovation is being carried out, through the “Plan Especial de Rehabilitación Integrada” of the area of Txabarri-El Sol, leaded by Sestao Berri agency. The key aspects of one of the successful energy retrofitted buildings were based on sustainable materials, the integration of biomass and the inclusion of a new prepaid energy management system supported by smart meters and a data platform. In Milan (Italy), a large public building located in the outskirts of the city, owned by the Municipality of Milan, has been a replicated model for the “Zero case vuote”, a local plan for public residential buildings. This building underwent a mayor energy refurbishment which included the thermal improvement of the envelope, centralization of the DHW and heating system, followed by the connection to the district heating network, the installation of a centralized mechanical ventilation system and in a later phase, the installation of an exhaust-air heat pump for the production of DHW. A post-occupancy evaluation of the retrofitted buildings was performed after one year (Sestao case study) and two years (Milan case study) of energy monitoring. In both cases, high energy savings were obtained compared to the pre-retrofit situation, however the analysis showed a meaningful difference between calculated energy use and measured values after the implementation of the energy efficiency measures. In Sestao the measured energy use for heating was less than expected, while in Milan the energy use for heating was more than expected. These two case studies represent two different approaches dealing with energy retrofitting of social housing and low-income tenants. The study releases potential hypothesis regarding technical and social aspects involved in the causes of these performance gaps.
