A method of controlling an environmental control system comprising: providing an environmental control system that includes a processing system in operative communication with a heating system ; acquiring historical temperature information regarding heating of an enclosure during at least one historical period in which the enclosure was heated by the heating system under the control of said environmental control system ; characterized in that the method further comprises: determining a lag value that refers to the time required to raise the temperature of the enclosure by a defined amount after applying heat and that represents at least in part an amount of system inertia for the enclosure ; determining a plurality of candidate heating control strategies based on said historical temperature information; determining an optimal heating control strategy from said plurality of candidate heating control strategies by computing a plurality of predicted temperature responses corresponding respectively to the plurality of candidate heating control strategies, wherein said computing the plurality of predicted temperature responses comprises applying each candidate heating control strategy to a model of the enclosure that includes said lag value; and controlling the heating system according to the determined optimal heating control strategy. providing an environmental control system that includes a processing system in operative communication with a heating system ; acquiring historical temperature information regarding heating of an enclosure during at least one historical period in which the enclosure was heated by the heating system under the control of said environmental control system ; characterized in that the method further comprises: determining a lag value that refers to the time required to raise the temperature of the enclosure by a defined amount after applying heat and that represents at least in part an amount of system inertia for the enclosure ; determining a plurality of candidate heating control strategies based on said historical temperature information; determining an optimal heating control strategy from said plurality of candidate heating control strategies by computing a plurality of predicted temperature responses corresponding respectively to the plurality of candidate heating control strategies, wherein said computing the plurality of predicted temperature responses comprises applying each candidate heating control strategy to a model of the enclosure that includes said lag value; and controlling the heating system according to the determined optimal heating control strategy. determining a lag value that refers to the time required to raise the temperature of the enclosure by a defined amount after applying heat and that represents at least in part an amount of system inertia for the enclosure ; determining a plurality of candidate heating control strategies based on said historical temperature information; determining an optimal heating control strategy from said plurality of candidate heating control strategies by computing a plurality of predicted temperature responses corresponding respectively to the plurality of candidate heating control strategies, wherein said computing the plurality of predicted temperature responses comprises applying each candidate heating control strategy to a model of the enclosure that includes said lag value; and controlling the heating system according to the determined optimal heating control strategy. <EOS>