## 1 Introduction  
Thinking both with a view to sustainable buildings and to the evolution we have been witnessing in recent years as a result of issues such as climate change, pandemics, and the need to increase the productivity of the neighboring area, we cannot fail to consider issues such as hanging gardens and indoor cultivation. We talk about hanging gardens if you want to create a plant system on a waterproof structural support layer, such as concrete slabs, attics, wooden roofing, and metal roofing, and in all those cases in which there is no ecological continuity between the green and the subsoil up to the mother rock [1]. Hanging gardens can be extensive or intensive. The former are non-walkable green roofs that need minimal maintenance and an irrigation system that comes into operation only in the hottest periods; intensive hanging gardens, on the other hand, are walkable and require a deep substrate, an adequate irrigation system, and can accommodate fountains, trees, and even swimming pools. Hanging gardens play an important role in sustainable construction and environmental quality of buildings, bringing benefits in economic and environmental terms. The roof used as a garden helps to control the temperature and to reduce pollution. It contributes to create thermal insulation on summer air conditioning and winter heating with consequent savings in the energy management of the building. Moreover, thanks to chlorophyll photosynthesis, hanging gardens produce oxygen and reduce the amount of CO\({}_{2}\) in the atmosphere. In addition, the hanging gardens retain rainwater and reduce the phenomenon of urban heat islands. In other words, a green roof keeps all the technological and construction content typical of a traditional roof reproducing, in addition, the typical performance of a natural soil covered with vegetation, to a complete or limited extent. It can therefore be considered a compensation and mitigation tool for the impacts generated by the inclusion of new structural works in the territory, suitable for generating the formation of near-natural ecosystems in densely built-up areas [1]. The hanging garden must not be considered as a simple finishing and should not be applied as an ordinary building material, because this means not considering plants as living and complex organisms in dynamic and continuous evolutionary equilibrium with the external environment and in need of maintenance. The indoor cultivation technique allows you to grow any type of plant inside a closed environment, such as a grow box, a greenhouse, or a room, where all the stages of development and growth of the plant take place, from germination to flowering. Some advantages of indoor over outdoor cultivation are:  
* it is possible to control the whole crop, including the temperature, the time of exposure of plants to light, and when the plant will receive water;
* gives year-round cultivation regardless of season;
* it is possible to harvest more quickly since in an indoor crop gives to control the photoperiod of the plants;
* less exposure to pests or other bugs;
* it is a zero-kilometer technique;
* it allows the saving of more than 90% of water compared with traditional crops;
* any space can be used: just have the accessories and assemble your own grow;
* by having space, it is also possible to place multiple overlapping indoor crops (the so-called vertical farms);
* there is no dependence on sunlight, but it is necessary to have a suitable kit of lights that can recreate the optimal growth atmosphere for plants. Many also use the most modern LED lamps to decrease production costs. The 2020 World Population Data Sheet indicates that the world population is projected to reach nearly 10 billion by 2050, and the corresponding projection of the increase in food production is 70% compared with 25% in 2014 [2].