*3.2. Costs for Greening Systems*

The construction as well as the green care and technical maintenance of vertical greening systems comes with costs. These are divided into investment costs, which are incurred once when the greening system is set up, and ongoing costs for plant care and technical maintenance of the system. The calculations also include costs for electricity and water consumption for lighting and irrigation of the green areas. They are divided into costs for green care and technical maintenance including fertilizer, plant material, as well as water and electricity consumption.

The costs considered in the research of this article are based on the real consumption of electricity and water measured in one of the schools and on the costs for green care and maintenance for the company that took over the maintenance after the end of the research project. The necessary lighting of the vertical indoor greenery is provided by LED strips or spotlights. The irrigation is done by a connection to the house water pipe and a micro-drip system according to the needs of each of the two different greening systems.

Due to the different functionalities of the two greening systems under consideration, the water consumption and the costs for green care and maintenance also differ. While in the trough system the plants are placed in technical substrate, comparable to a conventional flower pot, in the fleece system three different fleece layers are used for protection as well as for water distribution and storage. Since the plants are inserted bare-rooted into the fleece system and the fleece serves as a substrate substitute, the water consumption is significantly higher than with the trough system. Since this characteristic makes the system less resilient, the costs for care and maintenance are also higher than for the trough system. A more detailed analysis and explanation of the costs are included in [47].

Due to the comparability of the systems at the three locations, these real costs per m2 known for one location are also used for the other two locations. Table in Section 3.5. contains the corresponding values for the six greened rooms.

The construction costs are incurred once only and are therefore allocated over the considered time period as shown in table in Section 3.5. This is done using a straight-line depreciation of the installation.
