La Citè (post) Industrielle. Efficienza energetica urbana

Main studies in energy saving in construction have demonstrated the restriction on benefits achievable with efforts mon buildings and the necessity of a “change of scale” moving from a single residential unit to the whole urban system. In fact, results attainable with energy saving policies applied on individual buildings tend to level off, requiring necessarily works on an ‘upper’ scale (urban or land scale) in relation to the city size and shape. In a time when energy world situation is asking for a transition toward new alternative sources, interesting research have already confirmed the deep relationship between energy consumptions and urban morphology through the study of some macro-classes of ‘physical’ parameters like: urban density, h/w ratio, settlement’s shape and size, microclimate, ecc. The re-reading of the city hystory from an energy viewpoint, shows the one-to-one relation that exists between spatial configurations, determined by urban design, and the corresponding energy balance. This relationship has been reasserted also by the foremost international organization (ONU, European Commission, etc.) which have indicated the urban design as one of the favoured tools to build the future ‘sustainable city’. Although today the actions on this topics are rapidly growing, settlements which can be defined in this way are really few. Difficulties found in this changeover can be ascribed also to the hidden meaning of ‘sustainaiblity’, whose comprehension entails overcoming an urban design ‘by parts’ in favour of an holistic approach which acts on the City seen as an ecosystem interrelated to its environment. This interdependence is chiefly revealed by input and output processes which govern urban metabolism. Even if the use of new local and renewable sources is a necessary condition to label a city like ‘sustainalbe’, it is insufficient unless accompanied with an appropriate consumption’s containment policy. The designer’s scant attention to the local weather and environmental conditions has been counterbalanced in the course of time by use of technologies with heavy consequences on global energy consumptions. The rude awakening from faulty belief on hydrocarbon’s limitless availability forces us to rethink the urban design process in function of ‘physical’ and environmental parameters which affected city energy behavior. In fact, the urban energy balance is deeply affected by spatial configurations resulting from typo-morphological initial choices among which the H/W ratio is gaining in importance. The significance that takes the correct urban design on subsequent energy behavior ascribed great responsibility to spatial solutions delineated during the early stage of the project, re-introducing again weather and environmental data among the basic information used by designers for the correct composition of their works.