Abstract: Method of operating an environment management system within a building uses each of at least a first and a second model to predict, for a chosen time period ahead, one or both of: i) control requirements for the environment management system in light of a current measured system state and a desired future system state or ii) a future system state that would be reached with a particular set of control inputs. The first model is a parameterised physical model of the building and the second model is an implicit model of the building. Prediction models are evaluated, a band of uncertainty determined, and a control strategy that minimizing a likely level of deviation from the desired future system state selected. The control strategy comprises control parameters for the environment management system. The environment management system controls the environment in the building in accordance with the selected control strategy.