A method for automatically operating a heating system controller for heating an indoor space so that the indoor temperature measurement signals are kept a) at approximately or above a default set point when the automatically obtained outdoor temperature indicator signals reflect an outdoor temperature indicator that is above a freeze protection point, or b) at approximately a computed set point that is higher than the default set point when the outdoor temperature indicator signals reflect an outdoor temperature indicator that is below the freeze protection point. The computed set point can be based on an outdoor temperature indicator. A heating system comprising a furnace, a thermostatic controller, a sensor of indoor temperature operatively connected to the thermostatic controller, a receiver operatively connected to the thermostatic controller for receiving a signal indicative of an outdoor temperature indicator, wherein the thermostatic controller is configured to operate according to the method.