A heating, ventilating, or air conditioning, HVAC, system for a building, the HVAC system comprising: a waterside system comprising waterside HVAC equipment configured to consume one or more resources from utility providers to generate a heated and/or chilled fluid; an airside system comprising airside HVAC equipment configured to receive the heated and/or chilled fluid from the waterside system and to use the heated and/or chilled fluid to heat and/or cool a supply airflow provided to the building; and a HVAC controller configured to receive inputs from both the waterside system and the airside system and perform an integrated airside/waterside optimization process to determine control outputs for both the waterside HVAC equipment and the airside HVAC equipment simultaneously such that the control outputs for the airside HVAC equipment are based on the control outputs for the waterside HVAC equipment and vice versa, wherein performing the integrated airside/waterside optimization process comprises using a predictive cost model to optimize a cost of the one or more resources consumed by the waterside system subject to optimization constraints comprising temperature constraints for the building and a constraint relating, for each resource of a set of resources comprising the heated and/or chilled fluid and the supply airflow, a production rate of the resource by a set of generators comprising the waterside HVAC equipment and the airside HVAC equipment to one or more flows of the resource into one or more zones of the building; wherein the HVAC controller is configured to provide the control outputs to the waterside system and the airside system for use in controlling the waterside HVAC equipment and the airside HVAC equipment. a waterside system comprising waterside HVAC equipment configured to consume one or more resources from utility providers to generate a heated and/or chilled fluid; an airside system comprising airside HVAC equipment configured to receive the heated and/or chilled fluid from the waterside system and to use the heated and/or chilled fluid to heat and/or cool a supply airflow provided to the building; and a HVAC controller configured to receive inputs from both the waterside system and the airside system and perform an integrated airside/waterside optimization process to determine control outputs for both the waterside HVAC equipment and the airside HVAC equipment simultaneously such that the control outputs for the airside HVAC equipment are based on the control outputs for the waterside HVAC equipment and vice versa, wherein performing the integrated airside/waterside optimization process comprises using a predictive cost model to optimize a cost of the one or more resources consumed by the waterside system subject to optimization constraints comprising temperature constraints for the building and a constraint relating, for each resource of a set of resources comprising the heated and/or chilled fluid and the supply airflow, a production rate of the resource by a set of generators comprising the waterside HVAC equipment and the airside HVAC equipment to one or more flows of the resource into one or more zones of the building; wherein the HVAC controller is configured to provide the control outputs to the waterside system and the airside system for use in controlling the waterside HVAC equipment and the airside HVAC equipment.