From “brutalist” to “sustainable” – the COIM shopping and office center in Potenza, Italy, becomes NZEB

Many designers of the buildings planned and then built in Italy and also worldwide in the eighties – even the most representative ones for public use, dimensions and architectural stateliness – have turned to “brutalist” architecture, derived from works by Le Corbusier, and later James Stirling, Denys Lasdun, Louis Kahn and Paul Rudolph. Just as Zaha Hadid and Tadao Ando will continue to do also in the Vitra Museum buildings in Weil am Rhein up to 1993, the extremism of the béton brut poetics has led to the construction of buildings with perimeter walls and roof slabs as well as roofs on unheated spaces devoid of thermal insulation, which, nowadays, turn out to be extremely costly to deal with, at least when they do not have serious thermo-hygrometric malfunctioning. The distinctiveness of the outer surface finish, as well as its importance for the appearance of the building structure, has made any kind of intervention difficult, because of the energy retrofitting involved, since the problems arising from an insulation from inside would be far more than those solved due to the thermal bridges created. Furthermore, it would prove to be economically unfeasible (particularly if it is well done), whereas an insulation from outside poses the problem of the alteration and loss of the distinctiveness of building structural surfaces. Built in the eighties, the Potenza COIM shopping and office centre shows in all its different parts an energy consumption – EPi, primary energy index – equal to 42,67 kWh/m3 per year, (whereas the index provided for by Italian standards is equal to 15,33 kWh/m3 per year). After a careful assessment of the seismic vulnerability of the structure, as well as a detailed environmental study, the choice made was that of working from outside according to EPBD 31/2010, which provides that, starting from 1st January 2021, all the buildings subject to renovation will have to be NZEB, with an ETICS with a mineral wool insulation and a finish very similar to that of reinforced concrete cast onsite, which is expected to reach a primary energy index – EPi – equal to 0,69 kWh/m3 per year. However, the utilization of aerogel ultrathin insulating layer and new generation triple glazing windows, the elimination of all the thermal bridges, the utilization of controlled mechanical ventilation in some areas, and, for the roof coverings, green roofs, as well as renewable energy produced locally, photovoltaic panels on tensile structures and micro wind turbines with vertical axis, allow the realization of the economic feasibility and project sustainability aims in respect to the original architectural configuration, thus suggesting an intervention model applicable to all similar cases.