The study looked at how a low-energy building in Copenhagen responds to changes in temperature. They measured heating energy use, room temperatures, and temperatures inside concrete walls and ceilings. In winter, some days had high temperatures set by occupants, while others had regular heating. In summer, the building overheated. Solar heat had a big impact in both seasons. The temperature inside concrete walls fluctuated, with the non-load-bearing wall showing the most change. Concrete walls took time to heat up or cool down. All concrete walls in the building can store heat. This research helps understand how concrete walls affect heating in low-energy buildings.