An Environmental Control System (ECS) is disclosed for providing conditioned air to a conditioned air space. The ECS includes one or more first modules, each with a turbofan engine or Auxiliary Power Un it (APU), a first heat exchanger, a first turbine, a first water collector, and a first auxiliary fan powered by the first turbine. The ECS also includes one or more second modules. Each second module includes a mixing manifold, a second heat exchanger, an optional second water collector, and a second auxiliary fan powered by a second turbine.