Un approccio indiretto innovativo per la valutazione del flusso di calore: proposta di un metodo termometrico migliorato

The increase in global air temperature due to anthropogenic greenhouse gas (GHG) emissions poses a significant challenge exacerbated by the accelerating trend of climate change, heavily influenced by continuous urbanization expansion. Cities consume about two-thirds of global energy and generate more than two-third of global CO2 emissions, with the building sector contributing approximately one-third of global energy consumption and more than one-quarter of CO2 emissions. Addressing the environmental impact of the building sector necessitates promoting energy requalification interventions for built heritage. A critical aspect of this effort is accurately characterizing building envelope thermal performance to identify structures requiring energy retrofitting. While various non-destructive techniques have been proposed, the thermometric (THM) method has methodological advantages and cost-effectiveness. However, the literature disagrees with the total internal heat transfer coefficient for indirectly calculating thermal flux across building walls. To clarify how to compute this coefficient appropriately, this research proposes an enhanced THM approach (E-THM), ensuring robust computation of the total internal heat transfer coefficient through a methodology based on dimensionless group analysis. The reliability of the proposed E-THM method was investigated through two experimental campaigns, one using a low-cost apparatus and the other an improved apparatus with enhanced thermal behavior. Based on the findings, the E-THM approach demonstrates promise in assessing the heat fluxes crossing the walls, with percentage differences ranging from 0.36% to 0.71% when compared to the Heat-Flow Meter (HFM) technique. Additionally, this research project integrates an assessment of the Urban Heat Island (UHI) phenomenon in Rome and its impact on building energy needs into comprehensive research on building energy renovation. The influence of weather data selection on simulations was also investigated, highlighting the role of green spaces and natural environments in mitigating urban overheating. Furthermore, dynamic simulations using different weather data were conducted to estimate heating and cooling energy demand for representative residential buildings, emphasizing the importance of considering UHI effects. Overall, the study underscores the prominent effect of urban overheating within the city and the necessity of employing climatic data from rural areas within cities as a reference to accurately assess both UHI intensity values and building energy performance, warning against reliance on airport-collected meteorological data for urban areas.