Abstract
It is well known that the application of interior insulation systems increases consistently the energy performance of historic buildings, but severely affects the drying potential of their envelopes, by reducing the evaporation potential towards the internal side. Several strategies have been implemented to face this side effect: among the others, in the cases where the wind-driven rain represents the most impacting environmental factor that could cause interstitial condensation, it is recommended to reduce the penetration of the wind-driven rain through the replacement of the original plaster with a "water-repellent" one. This, in order to decrease the permeability of the external surface to the liquid water coming from the wind-driven rain. Since such interventions represent big economic and environmental costs, there is a big need to identify whether they are necessary or not. In the German standard DIN 4108-3, the need for this type of intervention is decided only on the basis of the annual precipitation amount; this approach can hardly be extended to lower European latitudes, as it totally excludes the impact of the radiation, which may play a significant role on the water content of the envelopes as a consistent driver for evaporation phenomena. Moreover, the wind effect may be taken into account by considering the wind driven rain on the studied façade. These hypotheses are investigated in the framework of the "HyLAB" project, for the conservation and refurbishment of a protected industrial building located in Bolzano (Italy); the results from hygrothermal simulations are analyzed and compared to other climates with similar annual precipitation and different annual radiation amount, at lower and higher latitudes. Results shows that, regarding highly rainy climate with consistent amounts of solar radiation, the use of a water repellent exterior coating could be avoided. Moreover, regarding lower latitudes of Europe, there is currently the need of a more elaborated method for identifying the necessity of replacing the external coating; this method should include external climate factors, e.g. annual radiation and wind-driven rain.