## 5 Summary and Conclusions  
In times when it is necessary to recover water and relieve the pressure on water supply networks, alternative sources of water are being sought. A previous study gave an analysis of water recovery from the exhaust air for a cultivation hall. This system was not self-sufficient, because its effectiveness in the warmer period was very low. In areas with rainfall, rainwater recovery is popular, thus it is important to analyze its effectiveness for water supply to hydroponics. In this work, for the selected location (Wroclaw, Poland) and the assumed geometry of the plant hall, the effectiveness of rainwater recovery from the roof surface was analyzed. The calculations of the rainwater harvesting (RWH) system were carried out, considering the selection of the tank capacity for the collected water. The operation of the water storage was simulated using a yield after spillage (YAS) algorithm. It was evident that the proposed system might be an auxiliary system that relieves the water supply network or supports other water recovery systems (e.g., the water vapor condensation in a cross-flow heat exchanger operating as an element of the air conditioning system, proposed in Part 1 of this study). On the base of long term water recovery systems analysis, the rainwater harvesting system is a less stable source of water than water reclaimed from the air, comparing to the system recovering water from the exhausted air [4].  
In the summer season, the greatest effectiveness of rainwater recovery was observed. The annual average water-saving efficiency from the RWH system equaled 38.94% while the condense recovery system's effectiveness equaled 67.12%. Taking into account the relatively high effectiveness of the rainwater recovery system during the summer, a solution based on combining the two systems was proposed. An economic analysis of the combined system with a 12 m\({}^{3}\) tank was proposed which achieved an average water recovery for plant watering purposes equal to 90.4%. In 2018, there was a minimum water coverage of 84.0%. In 2012, there was a maximum water demand coverage of 95.1%. It may be concluded that a combination of both of the systems is a very efficient solution, allowing for a large reduction in tap water consumption for hydroponic lettuce cultivation.  
A.J., A.P. and B.K.; investigation, A.J., A.P.; resources, B.K.; data curation, B.K.; writing--original draft preparation, A.J., A.P., D.P. and B.K.; writing--review and editing, A.J., A.P., D.P. and B.K.; visualization, B.K.; supervision, D.P.; project administration, A.P.; funding acquisition, A.P. and B.K. All authors have read and agreed to the published version of the manuscript.  
[PERSON] and [PERSON] received financial support from Polish National Centre for Research and Development, pro-gram Lider X, agreement number U/0180/666/2019.  
**Informed Consent Statement:** Not applicable.  
**Acknowledgments:** In this section you can acknowledge any support given which is not covered by the author contribution or funding sections. This may include administrative and technical support, or donations in kind (e.g., materials used for experiments).  
**Conflicts of Interest:** The authors declare no conflict of interest.