Torrelago is a residential district located in Laguna de Duero, near Valladolid, formed by 31 buildings that respond to three different typologies, containing a total 1,488 dwelling where more than 4,000 residents live. The district is also characterized by its high construction density (198.4 dwellings/ha) and high population density (514.4 inh/ha) in relation to the other parts of the town. The district was constructed around 1980 and is divided in two administrative phases. It had become necessary a renovation of the buildings. The project of Torrelago involves façades retrofitting and renovation of the district heating system. The aims of the project are to reduce the energy demand by improving buildings insulation and greenhouse gas emissions and to increase the use of renewable energy sources (in three biomass boilers) by implementing innovative technologies and methodologies for building renovation. Moreover, it is intended to install a microcogeneration system, an efficient and clean approach to generate 33kW of electric power and 73.4kW of useful thermal energy from a single fuel source. The retrofitting started on January 2014 and it is expected to be finished by march 2018. The construction company assures a significant reduction in the energy demand of the buildings (40%) by the installation of external insulation on the façades. Thanks to the retrofitting in the district heating system, the share of energy savings is thought to reach 50%.