On an innovative approach for microclimate enhancement and retrofit of historic buildings and artworks preservation by means of innovative thin envelope materials

Energy efficiency and environmental sustainability in building has become a key issue since the built environment is nowadays responsible for more than 30% of the total carbon emissions. While new building design and construction reached massive improvements toward net zero energy and high environmental performance standards, existing and historical buildings are still too much energy needy, with a relatively low indoor comfort conditions for both occupants and artworks preserved inside, especially within heritage buildings. Such high architectural value buildings correspond to almost one third of the Italian building stock and they typically need to be re-functionalized for hosting residential, office, or institutional uses, i.e. museums and exhibition areas. In this view, the present research aims at developing a replicable method for assessing and enhancing indoor comfort in historical buildings frequently characterized by too high relative humidity and thermal losses through the envelope. More in details, an innovative envelope material for indoor application, i.e. hygro-adsorbing plaster, has been tested in an ancient Italian castle and its effect has been assessed by means of coupled monitoring and calibrated dynamic simulation. The experimental campaign shows an increase of the Performance Index (PI) in terms of relative humidity acceptable range from 16.1 to 33.3% by applying the new thin plaster. Moreover, the results show that dedicated HVAC systems may support the action of passive strategies for preserving artworks and indoor comfort levels, but at the same time, such passive low-invasive strategies represent a mandatory first step toward energy efficiency, functional, and comfortable cultural heritage architectures.