Assessment of equivalent thermal properties of multilayer building walls coupling simulations and experimental measurements

The growing effort of reducing energy needs in the building sector calls for an accurate characterization of theperformances of external walls, which are the main cause of thermal exchanges and consequently are fundamentalto realize accurate simulation models to evaluate and control thermal loads.The dynamic characterization of a multilayer wall can be performed by defining its stratigraphy and thethermo-physical parameters of each layer. When existing buildings are investigated, technical specifications maybe unknown or difficult to obtain due to documents lost over time; furthermore, aging may have altered thebuilding materials characteristics. In these cases, in-situ measurements become essential but there is the need toanalyze the behavior of walls considering their dynamic characteristics, not obtainable by employing non-destructivetests, such as the heat-flow meter method.The paper aims to verify if an equivalent homogeneous wall can be associated to a multilayer wall in the senseof producing the same behavior if exposed to the same outdoor environmental conditions. Findings in literaturedemonstrate that, generally, this is not exactly achievable. However, the possibility of an approximateequivalence is investigated in this work by means of finite-element simulations and experimental measurements.The results obtained in actual case studies show that this equivalence can be made, obtaining preliminary satisfyingresults. The proposed methodology can be employed in existing and historical buildings to achieveuseful equivalent data directly applicable for the energy retrofit phase and for achieving a better couplingbetween the building and the heating/cooling system, reducing environmental impacts.