Impact of interior insulation on residential room with eliminated balcony in hot-humid climates: empirical study in Chengdu, China

This study evaluated the thermal performance of interior insulation retrofits in residential bedrooms with eliminated balconies in the hot-summer and cold-winter (HSCW) region. Field measurements of temperature, relative humidity, and cooling energy consumption under intermittent operation were used to assess retrofit effectiveness. The results demonstrated that interior insulation stabilized indoor temperatures, reduced vertical and temporal variations, and mitigated humidity fluctuations, thereby enhancing thermal comfort and energy efficiency. Exterior-to-interior wall temperature differences reached up to 8 °C, with peak daily cooling energy savings of 43%. However, common local modifications that integrate balconies into bedrooms reduced the retrofit’s effectiveness, particularly in the former balcony areas. These findings emphasize the importance of evaluating energy retrofit performance in the context of residents’ self-initiated spatial modifications, providing practical guidance for optimizing comfort and energy efficiency in real-world residential settings.