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The popularity of urban agriculture and green roofs is increasing in cities around the world that recognize the multifaceted benefits to the local community. Rooftop plant production (RPP) systems can be used to grow ornamental plants or food crops using raised beds, row farming, or hydroponic greenhouse. RPP systems maximize the cultivation area of the plant factory with artificial lighting (PFAL). RPP can be used to grow crops that require higher light intensities and greater heights than those plants traditionally grown in PFAL. Further, seedlings started in a PFAL can be transferred to the roof and cultivated with RPP. The environmental benefits of RPP can be a great asset to the sustainability and resource use efficiency (RUE) of the PFAL, while also providing net-positive enhancements to the local community and urban landscape by increasing agricultural awareness, boosting the local economy, mitigating stormwater, and reducing the heat island effect.

Proper understanding of the nature and relationships among the environmental factors in a plant factory with artificial lighting (PFAL) is essential in order to control and maintain the optimum levels of the environmental factors to realize the maximum potential of plant production. This chapter describes the physical and chemical properties of the following environmental factors and their measurement: temperature, humidity, CO2 concentration, air current speed, and ventilation rate (number of air exchanges per hour) with regard to the PFAL. In addition, basic concepts of energy balance, radiation, heat conduction, and convection are described in detail. Furthermore, the concept and use of the psychrometric chart are introduced and discussed for their important roles in understanding the environmental control of PFALs.