Office spaces are characterized by strict constraints of thermal comfort and indoor air quality (IAQ) levels crucial for the occupants’ wellbeing and decision-making abilities. For these reasons, office spaces have large cooling loads especially in hot climates. Conventional vapor compression air conditioning systems are known to be energy intensive systems that rely mainly on electrical energy. Thus, there is a pressing need to decrease the reliance on active cooling systems by the introduction of passive cooling strategies and efficient sustainable buildings. This study proposes an effective passive cooling system that integrates a cross-flow dew point indirect evaporative cooler (DP-IEC) supplying cool clean air to an office space. Validated mathematical models were used to assess the integrated system’s ability in maintaining acceptable thermal comfort and IAQ levels at minimal energy and water consumption. The simulations were carried out for the peak load month for a case study of an occupied office located in the semi-arid and hot Lebanese inland region. The proposed system was able to meet the space thermal and IAQ constraints (average indoor temperature of 25.6 °C, CO2 concentration below 600 ppm). The optimized system operation yielded a daily energy and water consumption of 0.65 kWh and 52 L with a reduction of 80 % in the running cost as compared to the conventional mechanical system.