AbstractIn high-occupancy intermittent buildings, such as mosques and theaters, it is challenging to design proper air distribution systems and HVAC (heating, ventilating, and air-conditioning) operation strategies to maintain thermal comfort at reduced energy consumption. This study investigates the thermal and energy performance of a high-occupancy intermittently operated mosque in Saudi Arabia. DesignBuilder software (version v4.7) was used for the coupled energy and computational fluid dynamics simulations. The continuous HVAC operation results indicate an annual cooling energy consumption of 181 kW · h/m2, with only two under-floor air distribution system models [through-wall supply with eight diffusers at 3 m height and ceiling return (M5) and through-wall supply with 10 diffusers at 3 m height and wall return at 3 m from the ground (M6)] achieving thermal comfort with only a few cold spots in the throw areas. The intermittent operation saved 30% of the total annual energy consumption, reducing it from 181 to 127 kW · h/m2, in turn, saving 35% of the total cooling energy consumption. Intermittent HVAC operation cases achieved thermal comfort, except for the four-way ceiling supply and wall return (M1). Therefore, implementing intermittent HVAC operation strategies in high-occupancy buildings significantly reduces energy consumption, while achieving thermal comfort when appropriate air distribution strategies are employed. These results provide critical guidelines for the design and operation of proper HVAC systems.