Thermal characterization of building walls using an equivalent modeling approach

The dynamic thermal behavior of walls cannot be adequately characterized by their thermal resistance alone. Other parameters are needed to describe its thermal inertia, and this aspect is fundamental in massive buildings. This requirement clashes with the availability of technical data in a building stock where documentation is often missing. Starting from this, exploiting data related to the thermal behavior of walls along time, an equivalent representation of actual walls could be a viable solution. The main problem is to understand whether an equivalent representation of a wall can provide a satisfactory description of the thermal behavior of the real multilayer wall. Consequently, a methodological procedure for the identification of equivalent thermo-physical properties useful for walls thermal characterization is here proposed. Walls stratigraphy deriving from different historical periods (and representative of the Italian building heritage) were created through a finite-element software, setting dynamic boundary conditions. During the first phase of the study, equivalent representations were tested to comprehend if they can provide similar thermal behavior compared to the original multilayer configurations. According to the computed goodness-of-fit indexes, the results show that this equivalence can be satisfactory. In addition, experimental data from a case study building were used for an equivalent modeling under actual boundary conditions. The outcomes of this phase documented that, despite meeting ASHRAE criteria for NMBE and CV(RMSE), achieving satisfactory EF values for more complex wall stratigraphy remained challenging.