Energy retrofitting of buildings and hygrothermal performance of building components: Application of the assessment methodology to a case study of social housing

Any intervention on the envelope/HVAC system of existing buildings should start from the evaluation of the building’s envelope energy-saving options. Typical buildings critical from the energy standpoint are represented by social housings: in this case the energy-saving is not possible without the building’s envelope renovation. Their energy retrofit towards NZEB should be the next challenge: it is analysed in the present paper by proposing an evaluation procedure that takes into account different constraints and limits imposed by national laws, following the indications of the European Directives. To illustrate the calculation methodology a case study is examined, by comparing the U-values of the existing walls with the NZEB limits and with the limits considered for the energy refurbishment of the buildings. The insulation improvement of the reference walls depends on both the thermo-physical properties and the thickness of the materials used. The choice of the most suitable combination of material and thickness is related not only to the energy-saving, but also to the risk of vapor condensation that depends on the position of the insulating materials within the wall’s structure. Therefore, the outlined procedure takes into account both these aspects. Moreover, as the renovation design process involves a multiplicity of elements and parameters, the proposed procedure could be generalized to consider a wide list of characteristics and constraints that allow to guarantee the most suitable solution with acceptable costs.