This work aims at investigating the impact of an Earth-Air Heat eXchanger (EAHX) on the thermal comfort when it is added to a natural nighttime ventilation for a house located in Marrakech (Morocco), which is characterized by a hot semi-arid climate. The thermal behavior of the house associated with this cooling combination was assessed using dynamic simulations. Two transient models are used, the well-validated Type 460 model of trnsys software (Transient System Simulation) for the EAHX and a separate trnsys-based model for the building, recently validated using an onsite long-term monitoring of the house under study in the present work. Many configurations of the house ranging from the building without any passive technique to the building with envelope thermal insulation connected with the EAHX combined with natural nighttime ventilation strategy have been investigated. The results showed that the nighttime ventilation strategy alone keeps the operative temperature lower than the convenient 28 °C for 92% of the time during the cooling period. On the other hand, when the EAHX alone is used, the operative temperature is lower than 28 °C during 57% of the time during the hot season. Hence, it was concluded that the passive nighttime ventilation alone leads already to a great thermal comfort improvement; however, its combination with an additional EAHX system results in convenient temperatures lower than 28 °C for 99% of time during the complete cooling period. It is found also that by applying nighttime ventilation, the air blowing flowrate can be reduced by up to three air change per hour while keeping the same EAHX’ parameters.