Impact of Floor - Ground Coupling and Thermal Mass on Seasonal Heating Energy Use in Single - Storey Residential Buildings in a Temperate Climate

This study presents an empirical evaluation of winter heating performance in two full-scale single-storey residential buildings located in a temperate transitional climate in western Poland. The buildings, identical in geometry, layout, and insulation levels, differed in wall thermal mass and subfloor configuration. During the 2018/2019 heating season, the building with medium-weight masonry walls consumed 3.6% less heating energy than its lightweight timber-frame counterpart. In the following season, floor insulation was removed in the masonry building to enable direct ground coupling. While this led to a 12.2% increase in total energy use, the difference emerged only in the latter part of the winter. Continuous ground temperature monitoring confirmed that subsoil heat retained from summer acted as a thermal buffer, delaying the onset of increased losses. The actual energy penalty was substantially lower than predicted by standard calculation methods, indicating that steady-state models may overestimate seasonal ground-related losses. These findings highlight the dynamic nature of heat exchange between buildings and the ground and support the use of mass-based and soil-coupled envelope strategies as effective tools for improving seasonal energy efficiency and resilience in temperate climates increasingly affected by climate variability and power supply risks.