Energy poverty is a common issue in social housing all over Europe, with a harder impact in Southern European countries. Social housing buildings play an important role in energy poverty. They are usually owned and managed by public institutions and usually share common characteristics and issues. Behavioural changes and energy retrofitting are interesting paths forward but some solutions do not fit well in this type of housing due to socioeconomic reasons. This paper makes a thorough analysis of possible energy efficiency measures in social housing buildings, characterizing them by energy and economic savings and investment and proposing different methods of prioritization. A rational approach of behavioural and retrofitting solutions that best fit into this particular housing type is delivered, with the aim to increase the thermal comfort of the residents and mitigate the energy poverty issue. Results show that there is a wide range of domestic efficiency measures to be applied in this type of dwellings at none or low costs, bringing annual savings per average dwelling of about 510 €/year (55% of initial energy costs) including measures both at domestic level, and at building level with a final aggregated payback of the investments to be about 1.5 years.

In developed countries, a large part of the building stock in 2050 will consist of currently existing buildings. Consequently, in order to achieve the objectives in terms of energy efficiency in the building sector we must consider not only new infrastructures but also the old ones. A reduction in energy consumption for climate control of between 50 and 90% can be achieved by rehabilitation and the implementation of different energy efficiency measures. Currently, these measures to reduce energy consumption and associated CO2 emissions can be modelled using computer tools. However, high precision and detail of thermal behaviour models through simulations can mean a great computational cost for companies, which results in a blockage of servers and workers. In this paper, the Response Surface Methodology (RSM) is presented as an innovative methodology for the simplification of models for calculation of the energy savings associated with thermal comfort improvement in buildings. A single-family house model, located in three different climates, is presented as a case study in order to validate the proposed methodology. Different scenarios were simulated, addressing heating and cooling temperature set points and external wall insulation represented by the transmittance (U-value). Results obtained from energy simulation using Design Builder were contrasted against those estimated from the simplified model extracted from the RSM analysis. The results revealed a deviation lower than 3% when comparing both methods. Therefore, the simplified mathematical prediction models are demonstrated to be suitable for the study of the energy performance of buildings, saving computational time, costs and associated human resources.

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Resumen En España, donde existen más de 18 millones de hogares según el último censo del Instituto Nacional de Estadística en 2011, alrededor del 8% de la población reside en viviendas de alquiler social. Del parque de viviendas español, más de la mitad de los edificios se construyeron antes de 1980 y alrededor del 35% entre 1981 y 2006, año en que fue implantado el Código Técnico de la Edificación. Asimismo, más del 80% de los certificados energéticos de edificios existentes registrados hasta julio de 2015, obtiene una calificación E o inferior en términos de emisiones de CO2. Para mejorar estos resultados, la Unión Europea tiene como objetivo alcanzar una tasa de rehabilitación de edificios privados del 2,5% anual, mejorando la eficiencia energética y ampliando la vida útil del parque edificatorio. Sin embargo, los CEEE únicamente representan parte de la etapa de uso, dejando atrás otras, como la de producción, cuyo impacto puede representar un cuarto de las emisiones de CO2 del edificio a lo largo de su ciclo de vida. Para desarrollar una rehabilitación óptima, se propone evaluar la sostenibilidad de los proyectos de rehabilitación incluyendo las etapas de producción, construcción, uso y fin de vida y considerando el impacto medioambiental y económico, así como aspectos sociales relativos a las características de la vivienda social. Este artículo analiza los impactos medioambientales de diferentes soluciones de rehabilitación en vivienda social, tomando como caso de estudio un edificio de vivienda social en Zaragoza. El edificio antes de la rehabilitación supone casi 50 kgCO2-eq/m2año, donde el 60% corresponden al consumo eléctrico durante la fase de uso del edificio. En el estudio también se incluye la variable de confort térmico en situaciones de vulnerabilidad energética. Abstract In Spain, where there are more than 18 million households according to the last census of the National Institute of Statistics in 2011, around 8% of the population lives in social rental housing. Of the Spanish housing stock, more than half of the buildings were built before 1980 and around 35% between 1981 and 2006, the year in which the Technical Building Code was implemented. Likewise, more than 80% of the energy certificates of existing buildings registered until July 2015, obtain an E rating or lower in terms of CO2 emissions. To improve these results, the European Union aims to achieve a private buildings rehabilitation rate of 2.5% per year, improving energy efficiency and extending the useful life of the building park. However, CEEEs only represent part of the use stage, leaving behind others, such as production, whose impact can represent a quarter of the building's CO2 emissions throughout its life cycle. To develop an optimal rehabilitation, it is proposed to evaluate the sustainability of the rehabilitation projects including the stages of production, construction, use and end of life and considering the environmental and economic impact, as well as social aspects related to the characteristics of social housing. This article analyzes the environmental impacts of different rehabilitation solutions in social housing, taking as a case study a social housing building in Zaragoza. The building before the rehabilitation supposes almost 50 kgCO2-eq / m2año, where 60% correspond to the electrical consumption during the phase of use of the building. The study also includes the thermal comfort variable in situations of energy vulnerability.