Criteria for promotion of low energy buildings in Europe. The Italian case

Lots of European Countries are promoting and sharing a sustainable building approach to be in compliance with the Kyoto Protocol and subsequent international agreements. Environmental protection and energy saving characterize some strategic European experiences. Assuming that buildings consume too much, in terms of environmental and economic resources, it is necessary to adopt different criteria to reduce energy consumption, to be defined in relation to climate zones. The Passivhaus standard, which defines low energy buildings with heating not dependent on fossil fuel, was originally developed in the Central Europe countries and recently it is being revised to adapt its criteria to different climate contexts, especially the Mediterranean one. In warm area the energetic efficiency is related to summer performances and passive cooling of buildings. Significant experiences are developing even in Italy, where the Mediterranean climate has different characteristics compared to the cold climates of central and northern Europe. The Italian territory is characterized by different climatic variables: those predominantly cold (Alpine) and those ones warm (southern and island regions). There are also areas with variations of temperature and humidity related to significant seasonal periods. The design strategies in terms of new construction and upgrading of existing buildings are based on the concept that building is a composite system, where the architecture, the layout of fronts and openings, the performances of building shell and integration with the fixtures and fittings, also powered by renewable sources, must be efficiently balanced. In general, to improve the energy performance of buildings, it is necessary to be focused on methods and systems essentially directed to reduce thermal transmittance of the shell. It is appropriate to take into account that in warm climates is important to ensure in the same time the insulation and the thermal inertia of the envelope. Therefore it is also necessary to consider massive technical solutions that can provide a sufficient lag time of temperature variations between external and internal. In conclusion, the recent increasing attention about the energy buildings efficiency highlights the technical and regulatory issue, about the search for best solutions for specific environmental conditions.