A method of controlling air flow in an environmental control system includes receiving a target total flow value and a combined flow measurement at an outer control loop module. A first air flow reference value is determined based on the target total flow value and the combined flow measurement using the outer control loop module. The first air flow reference value is communicated to an inner control loop module and a flow control valve command determined based at least in part on the first air flow reference value using the inner control loop module. The flow control valve command is communicated to a flow control valve operatively associated with the inner control loop module to control flow through the ECS using the flow control valve. Environmental control systems and computer program products are also described.