Table 3 Summarized measurement results of the U value of the flat roof for three different conditions regarding the roof layers
Measurement description | Measurement period | Average outdoor temperature | Average indoor temperature | Average temperature difference | U value (sensor set 1) | U value (sensor set 2) | Difference between sensors | Difference regarding previous condition of flat roof—sensor set 1 | Difference regarding the previous condition of flat roof—sensor set 2 |
|---|---|---|---|---|---|---|---|---|---|
°C | °C | °C | W/m2K | W/m2K | % | % | % | ||
M1—flat roof before building energy refurbishment | 20.12.2019–2.1.2020 | 5.36 | 27.45 | 22.09 | 1.4993 | 1.6384 | − 9% | – | – |
M2—flat roof after application of thermal insulation | 5.1.2021–28.1.2021 | 3.93 | 27.81 | 23.88 | 0.3706 | 0.3645 | 2% | 75% | 78% |
M3—flat green roof | 20.1.2023–2.2.2023 | 1.97 | 17.75 | 15.78 | 0.1156 | 0.1823 | − 58% | 69% | 50% |