On the ageing and weathering effects in assembled modular facades: On-site experimental measurements in an Italian building of the 1960s

Abstract The Heat flow Meter ( HFM ) method is a non-destructive technique used to evaluate the thermal transmittance (U-value) without damaging walls when the stratigraphy is unknown. However, not all walls have an optimal orientation to perform HFM measurement. Walls facing north are certainly desirable to exclude solar radiation effects. Nevertheless, there may be several constraints that impose to perform measurements on not perfectly oriented walls. In addition, it is worthy to observe that aging and weathering effects in old buildings can influence thermal performance, altering the thermophysical properties of materials. Architectural elements apparently identical may be different from a thermal point of view, for example because of ageing or weathering effects. So, one-spot measurements could be not always representative of the entire building envelope, especially in old buildings. Here, the HFM technique was came up beside the Temperature-Based (TB ) method, where an evaluation based on the dimensionless numbers’ assessment was performed to obtain the total heat transfer coefficients . Measurements were performed both on a north and north-west facing wall. The heat fluxes measured through the HFM method were compared with those obtained through the TB approach, and data were used to calculate the U-values of the walls. To investigate and avoid the influence of solar radiation, all data and only data logged during nights were used and compared. All data were used within a methodological approach able to provide results in terms of thermal discrepancies in a 60-year-old building, with a percentage increase due to ageing and weathering of about 56%.