In Situ Measurement of Wall Thermal Properties: Parametric Investigation of the Heat Flow Methods Through Virtual Experiments Data

Energy retrofit of existing buildings is based on the assessment of the starting performance of the envelope. The procedure to evaluate thermal conductance through in situ measurements is described in the technical standard ISO 9869-1:2014, which provides two alternative techniques to process collected data: the Average Method (AM) and the Dynamic Method (DM). This work studies their effectiveness using virtual data from numerical simulations of three kinds of walls, performed using a Finite Difference model. The AM always provides acceptable estimates in winter, with better outcomes when indoor heat flux is considered in every case except the highly insulated wall. Summer conditions do not lead to acceptable measurements, despite the fulfillment of the check required by the standard. The DM results show acceptable estimations of the thermal conductance in both climates, for most of the virtual samples considered, although critically depending on some parameters of the DM that are left to the user’s discretion, without strict indications by the standard. This work highlights a possible approach for overcoming this issue, which requires deeper future investigation