In cold climate regions, closed greenhouses with minimal ventilation minimize the energy requirement for heating compared to open-ventilated greenhouses. In this paper, a model of a closed greenhouse with Earth-Air Heat Exchanger (EAHE) heating is presented and simulations are performed using climate data of a representative day of the coldest month of the year (i.e. January) at the case study location, Hurghada, Egypt. A comparison is made between a closed greenhouse with and without EAHE heating. The simulations show that without heating the greenhouse interior temperature drops below the minimum temperature for cultivation (20°C) during the early and late hours of the day. Furthermore, at midday the temperature inside the greenhouse exceeded the maximum temperature for cultivation (30°C). The results showed that EAHE enabled the greenhouse interior to be maintained at a temperature suitable for plant cultivation, cooling during the day and warming at night. Further, the variability in relative humidity was reduced from 35% to 15%, simplifying the control of the humidity within the greenhouse. Additional simulations that cover the winter period (November to February), demonstrated that the EAHE is a viable sustainable method for temperature regulation without any requirement for additional heating.