The building envelope: a future beyond the concept of thermal insulation

Building envelope has always been considered a key element to provide an ade-quate comfort level within buildings and to assure an optimal energy performance. Recently, its importance and centrality for the energy efficiency of buildings was even more strengthened by the growing awareness of the need to reduce the production of greenhouse gases (especially CO2) and to significantly limit the consumption of fossil fuels. In particular, the new European legislative framework (2010/31/EU Energy Per-formance Buildings Directive – EPBD recast) sets the ambitious objective that, within 2020 all the new buildings (2018 for public buildings) will have to satisfy the “Nearly Zero Energy Building” (nZEB) target. The way towards the innovation of the building envelope, that today appears far more promising, consists in passing from the concept of “insulation” to that of “integra-tion and multifunctionality”. This requires the transition from a “passive” or resistive component (recurring to the well-known electric analogy for the heat transfer) to an “ac-tive” component, where the networks become resistive and capacitive and are integrated with generation/conversion systems, as for example, the technologies for the on-site conversion of solar radiation.