Includes the same features as the 31-1924, but also includes a built-in thermostat that allows the fan to operate at one of three preselected speeds when the thermostat calls for cooler air. Once the thermostat is satisfied, the fan automatically shuts off. Helps keep pets comfortable while your away and ventilates the air while you sleep. Polycarbonate dome opens manually. Fits standard 14″ x 14″ roof openings.