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Improvement of the energy efficiency of a rationalist building

Environment and Energy

University of Bologna Team Leader: Prof. Zanchini Enzo - Professor - Dep. of Energy, Nuclear and Environmental Protection Engineering.

University of Bologna Research Group: Ing. Stefania Falcioni, Prof. Gian Luca Morini.

Context and objectives

The main barrier to the diffusion of energy retrofit applications to existing buildings is the intervention cost. Usually, the economic payback time of an energy retrofit intervention exceeds 10 years; thus, public support policies appear as necessary to achieve a broad diffusion of retrofit techniques.

The energy retrofit is particularly difficult in the case of historic buildings, where an external thermal insulation of the lateral walls cannot be performed.

The aim of this paper is to study the energy efficiency of a Rationalist building in Bologna and to propose some retrofit techniques to improve this efficiency without modifying the external look of the enclosure.

The building, constructed by the architect Giuseppe Vaccaro between 1933 and 1935, is now the main site of the School of Engineering of the University of Bologna; it is considered one the most important examples of Italian rationalist architecture.

Methodologies and equipment

The study has been developed in three steps.

First, all the necessary data on the architecture, on the enclosure materials and on the heating plant have been collected. Then, the energy use for space heating has been evaluated. Finally, two retrofit scenarios have been considered.

In scenario 1, the terrace floor is provided with a 6 cm thick insulation made of expanded polystyrene (l=0.028 W/(m K)). In scenario 2, the conditions of scenario 1 are reproduced; moreover, the windows are replaced by double-glass windows with a glass transmittance Ug=1.8 W/(m2 K) and the boilers and the control system of the heating plant are replaced. For each scenario, the financial payback time, the energy payback time and the life-cycle energy saving have been determined.

The primary energy use for space heating in the present state, as well as in the retrofit scenarios considered, has been evaluated by means of the software package Mc4 suite.


The feasibility of energy retrofits of Rationalist buildings has been investigated by considering two retrofit scenarios of the School of Engineering of the University of Bologna (North-Centre Italy).

The most interesting scenario includes the thermal insulation of the terrace floor, the replacement of windows, the replacement of the boilers and of the thermal control system. It yields a 43% reduction of the primary energy use with a financial payback time of 8.0 years and an energy payback time of 0.9 years.

The reasonable value of the financial payback time and the very low value of the energy payback time suggest that interventions of this kind, in similar climatic conditions, should be supported by national governments and by the European Union.