The Solar Greenhouse: A Strategy for Energy Savings in Social Housing in Milan

The recently updated Lombardy Region law no. 39/2004 and the new Milan city building code stimulate more and more the use of passive climate control strategies to reduce thermal energy consumption. Solar greenhouse is one of the strategies promoted by regulations both for new and retrofit buildings. This chapter compares solar greenhouse regulation requirements (orientation, natural ventilation, openings, shading devices, etc.) with the Milan city public housing policies and programmes. In particular, it focuses on the large public building stock produced between the post-second war period and the 1980s, which has a very low energy performance and therefore high retrofit potential. Both the regional law and the building code consider greenhouse retrofitting by closing balconies or integrating building elements, such as the “loggia”. The solar greenhouses are feasible only if they reach at least a 10 % energy savings, calculated in accordance with the UNI EN ISO 13790/2008 (energy performance of buildings—calculation of energy use for space heating and cooling). The closing of balconies and loggias, especially in social housing, is an action that has often been made to increase the space available in the residence. However, the closing is often individual unauthorized action followed by subsequent amnesty and payment, which legalizes the increased volume and the facade change, independently by any energy performance evaluation. The consequence of individual uncontrolled actions is the change of facades, which often radically modify the visual impact of the residential complex, out of any facade image of the entire building. This chapter analyses a case study of a 1940–1950s social housing building in Milan. The selected case is a linear building with a mix 1/2/3-bedroom flats which have the requirements of the legislation to implement the bioclimatic greenhouses. Over the years, many flats became private property and many of the loggias were closed actually becoming real bioclimatic greenhouses. This chapter specifies the actual energy savings and takes into account the potential visual impacts that would occur with an action controlled and bound by guidelines provided by the local authorities and by the Lombardy public housing company (Aler).