Formulating cost-effective and environmentally friendly energy retrofitting strategies for the existing building stock is a complex task due to the heterogeneity of this sector. The aim of this paper is to present an ongoing research project which is developing a model for assessing the suitability of energy efficient retrofitting measures and their corresponding economic and environmental performance in the existing stock of offices. The project draws upon the energy performance certificates database, including more than 13,000 office certificates issued in Catalonia since the entry into force of the Royal Decree 235/2013. First of all, a k-means clustering algorithm is used to identify office clusters and their centroids. Secondly, the closest energy performance certificate to each cluster centroid is selected from the database, prioritizing those simulated with the general procedure (HULC) but using those with the simplified procedure (CE3X) when needed. The energy performance of implementing several energy saving measures in each representative office is simulated using the general (or the simplified) energy performance procedures. Simultaneously, the corresponding economic and environmental performance are assessed taking into account the whole life cycle of the energy saving measure(s). Finally, an integrated model for assessing the energy efficiency improvement of the existing stock of office buildings is developed taking into account the energetic, the economic and the environmental impact. The project is expected to stimulate the existing energy retrofitting market, since the developed model can be useful during the decision making process for office owners or managers, public organizations aimed to promote the energy efficiency of the built environment, professionals related to building retrofitting or energy service companies.

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