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

Abstract

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 energysaving 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.

A procedure to evaluate the most suitable integrated solutions for increasing energy performance of the building’s envelope, avoiding moisture problems

“…The methodology indicated in [8], completed by means of an economic investigation with the costs evaluation procedure [14], is reported in Fig.1.…”

“…The method described in [8] allows, through these steps, to determine the amount of condensation and evaporation for each month.…”

“…The calculation methodology, previously proposed [8] has been extended: it was developed mainly to achieve the energy saving objectives jointly with the respect of the constraints about vapour condensation inside walls, and now details on the cost analysis have been added. The whole methodology is here outlined.…”

“…An evaluation procedure, previously proposed [8], is applied to a case study represented by a common building unit located at an intermediate floor of a tall building.…”

Cost optimal analysis of energy refurbishment actions depending on the local climate and its variations

“…• Refurbishment options -Calculations: analyses of some solutions for the insulating improvement to obtain low U-values that are compared with the Refurbishment and nZEB U-values (Table 4) [14]. STEP 6 -Cost optimal evaluation.…”