*3.4. Improvement of Hygrothermal Comfort*

The measured data were evaluated according to the filter criteria and definition ranges for hygrothermal comfort (Figure 2) explained in Section 2. The results of these evaluations are shown in Table 2, and for one of the buildings as an example in Figure 4. It is clearly visible that the point cloud of the measurement data of the greened rooms (green measurement points) has clearly shifted into the comfortable area compared to the non-greened reference room (blue measurement points).

Based on the evaluations, it was calculated to what extent the greened rooms improve in comparison to the non-greened reference room. This percentage improvement is shown in Table 2. It can be clearly seen that all six greened rooms offer significantly higher hygrothermal comfort in comparison to the non-greened rooms and therefore have a healthier indoor climate. This also means that at no time was relative humidity too high, as is illustrated in Figure 4 for Building A as an example, so there is no risk of mold.

Due to the applied filter criteria explained in Section 2, these evaluations of the measured data obtained in school classes can also be applied to office rooms and, in particular, statements can be made about the winter period, which is important for sick leave due to respiratory diseases. The analysis of the monetary connection between the improved air quality and the days of sickness is presented in the next subchapter.

**Figure 4.** Hygrothermal comfort in not greened reference room and two greened rooms (fleece and trough system) for winter period represented by measured air temperature and relative air humidity with applied filter criteria (Building A).

**Table 2.** Evaluation of the measured data on hygrothermal comfort in the greened rooms compared to the reference rooms.

