Within-Building Variability in Summer Thermal Performance: A Case Study of a Swedish Multi-Residential Building

Paper in proceeding, 2025

In the heating-dominated Nordic countries, wintertime has traditionally been the primary focus in multi-residential buildings. However, the increasing frequency of heat waves raises concerns about the issue of overheating during summertime. A preliminary analysis of existing data resources of monitored indoor air temperatures in multi-residential buildings shows signs of overheating risk in several buildings in the region of Gothenburg. This study investigates factors influencing inter-apartment variability in thermal performance within a multi-residential building in Gothenburg, Sweden. Indoor air temperature data from 2018-2024 was analysed for 47 apartments across two identically constructed buildings. Degree hours above 26°C were used as an indicator of summer thermal performance. The analysis revealed substantial variability in thermal performance between apartments, with some consistently warmer or cooler than average across years. A declining trend in overall degree hours was observed from 2018-2024, potentially due to changes in ventilation control strategies. The influence of physical factors was examined, including floor level, apartment location, size, building section, and external shading. Floor level showed the strongest influence on degree hours, with upper floors generally experiencing higher temperatures. However, considerable variation was still observed between adjacent apartments, suggesting the formation of localized heat clusters. The presence of external shading objects considerably reduced degree hours. Apartment location (interior vs. corner), size, and building section had minimal impact on thermal performance. However, corner units exhibited greater temperature variability and reactivity to outdoor conditions compared to interior apartments. Hourly temperature analysis of selected apartments demonstrated varying thermal behaviours. Ground floor apartments maintained more stable temperatures, while upper floor apartments showed greater responsiveness to outdoor temperature fluctuations and solar radiation. The study highlights the complex interplay of physical factors influencing apartment-level thermal performance within multi-residential buildings. While general trends were observed, unexplained variability between adjacent units suggests the need for further investigation into intercorrelation between building parameters.