Energy Retrofit of Social Housing with Cultural Value in Spain: Analysis of Strategies Conserving the Original Image vs. Coordinating Its Modification

Two renovation strategies were considered and compared in this paper for the energy renovation of social housing in condo buildings built in 1945-1969, situated in residential estates that have been declared urban areas of interest. One of the strategies, named here the image conservation approach, consists of renovating the building with very efficient solutions, except for the brick-facing walls, which will only have insulation in the existing cavities. The other strategy, the image coordination approach, consists of renovating the whole building with efficient solutions, including external insulation for existing brick-facing walls, and drawing up coordination plans for each of the residential estates in order to guarantee a coordinated new image of the residential estates. By means of three case studies in the city of Zaragoza and four scenarios of improvement, the two strategies are compared regarding the regulation compliance, the energy use, the emissions reduction, the thermal comfort, and the cost-effectiveness of the measures. The results show that the image coordination approach is the best strategy in regard to the studied aspects, achieving a 69%-79% reduction of CO(2)emissions and a 75%-97% reduction of heating use, as well as being the only one capable of transforming these buildings into nearly zero energy buildings (nZEBs).