*Article* **Indirect Economic Effects of Vertical Indoor Green in the Context of Reduced Sick Leave in Offices**

**Jutta Hollands \* and Azra Korjenic**

Research Unit of Ecological Building Technologies, Institute of Material Technology, Building Physics and Building Ecology, Faculty of Civil Engineering, Vienna University of Technology, A-1040 Vienna, Austria; azra.korjenic@tuwien.ac.at

**\*** Correspondence: jutta.hollands@tuwien.ac.at

**Abstract:** Low indoor humidity has been shown to influence the transmission of respiratory diseases via air. A certain proportion of sick leave in offices is therefore attributable to dryness of air. An improvement in these conditions thus means a reduction in sick leave, which is accompanied by cost savings for companies. Vertical indoor greening has a verifiable positive effect on air humidity, especially in winter months. In this article, the correlation between improved air humidity in greened rooms and reduction of sick leave due to improved air humidity was described. The resulting indirect economic effect was determined by comparing the costs for construction, green care, and technical maintenance of indoor greenery with savings due to lower sick leave. Based on long-term measurement data on air humidity and temperature, and actual cost values for three buildings, located in Vienna, Austria, with 6 greened and 3 reference rooms without greenery, the correlation of the method was derived and finally formulated in a generalized way using dimensioning factors. Only considering the influence on air humidity, profitability of 6.6 m<sup>2</sup> vertical greening installed in an example office with six workplaces equipped with technical ventilation and saving of two sick days already results after about 4.5 years.


**Citation:** Hollands, J.; Korjenic, A. Indirect Economic Effects of Vertical Indoor Green in the Context of Reduced Sick Leave in Offices. *Sustainability* **2021**, *13*, 2256. https://doi.org/10.3390/su13042256

Academic Editor: Roberto Alonso González Lezcano Received: 2 February 2021 Accepted: 17 February 2021 Published: 19 February 2021

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**Keywords:** hygrothermal comfort; indoor green; vertical greenery; indoor air quality; cost-benefitratio; sick leave; absenteeism; alternative quantification method
