A monitoring campaign introducing the indoor driving temperature to assess the building envelope performance

In the last decade, residential buildings have significantly contributed to global energy demand, leading European countries to implement incentive policies promoting energy retrofitting, such as Italy's Superbonous 110 % scheme. Consequently, numerous studies have strived to elucidate the diverse impacts of building retrofitting by analysing various thermal parameters. To advance this knowledge, a methodology to assess the effect of envelope renovation by monitoring and investigating the indoor temperature fluctuations at various dwellings' nodes during the heating season is presented. The methodology adopts a data-driven approach and is applied to an insulated and a non-insulated building selected across the same neighbourhood as a case study. The experimental approach discriminated the indoor temperatures from the temperatures near the external walls, affected by radiator activation and heat transfer through the vertical envelope. Finally, the collected data are formulated to account for the building envelope performance also presenting a new devoted index. The results obtained for the case study indicate that envelope insulation reduces thermal energy use between 19 % and 56 %, while it increases the average room temperature up to 3 °C more than the standard setting, offering a further potential for energy saving up to 10 % driven by users' behaviour. These findings hold crucial implications for energy policies of retrofit strategies, providing essential information and evidence for considering possible consequences of building envelope renovation.