This work proposes a design procedure for a smart Fuzzy-based HVAC controller to be used in mosque buildings. A case study of Dubai climate has been chosen to demonstrate the design procedure in detail. The fuzzy controller input variables involve the inside temperature of the mosque space, the temperature difference between inside and outside the space, the dew-point temperature, and the population percentage of the space, defined as the ratio between the number of occupants inside the building, and the total building occupancy. The output of the fuzzy model is the compressor speed, as a percentage of the maximum speed. The method of designing the membership functions and setting the fuzzy rules is shown for each input and output variable based on the current literature. Operation curves have been generated for three months: January, April, and August to represent the diverse climate conditions of Dubai city over the year. The proposed smart controller is expected to lower the energy consumption of the building HVAC system. Moreover, the smart controller can keep the space within the desired comfort zone, while being able to adapt to any change in the input variables.