Towards a User-Centred Assessment of Building Envelope Retrofit Effects in Summer Season: Insights from an Application to Social Housing

In light of climate change, the European Renovation Wave aims to boost building renovation due to their fragilities (i.e., aged and inefficient stock) and importance on human lives. Financial incentives have been introduced for energy performance improvements in residential buildings, particularly lower-income housing, with primary application of traditional retrofit measures, such as external thermal insulation, window replacement, and space conditioning. Their efficacy has been widely confirmed in winter season for improving heating energy consumption. However, the suitability of these strategies in cooling season remains understudied along with retrofit economic assessment prioritized above social aspects and end-users dimension. This paper investigates the impact of building envelope retrofits on indoor environmental conditions, cooling energy consumption, and occupants’ satisfaction with the renovation in summertime. To this aim, a holistic approach combining measured data in 6 rooms of 3 households in two residential social housing buildings (objective perspective) and occupant surveys (subjective perspective) was adopted. The comparison of the pre and post renovation periods highlights mixed results: positive effects were observed in north-facing rooms, where retrofits reduced indoor temperatures and cooling energy demand (up to 30%); negative effects were detected concerning and increase in relative humidity and CO2 concentration and indoor temperatures in south-facing rooms despite increased air conditioning use (up to 13%). These findings underscore the limitations of traditional retrofit strategies during the cooling season, thus highlighting the need for alternative and tailored retrofit solutions like innovative passive cooling technologies, such as Ventilated Permeable Roofs and HERO-Tile Based Roofs.