A virtual thermostat to control an air condition of any target zone in an HVAC controlled space. The thermostat comprising of a 3D scanner to provide a 3D point cloud of the controlled space; a CAD-application algorithm to modify the point cloud into a 3D model of the space; a control panel for a user to input a set of boundary and initial conditions and a desired air condition at the target zone inside the controlled space; a fluid flow software having means to read said 3D model and to determine a spatial velocity and temperature distributions throughout the controlled space, and to calculate an average temperature for the target zone in the controlled space; a control system to manage the air inlet flow to control the temperature at the target zone in the controlled space by comparing the calculated average temperature of the target zone with a user defined temperature and to turn the HVAC system ON and OFF.