A demountable overhead utility cover unit is provided for use in a building room having a generally open plan for the purpose of transitioning between ceilings of different heights. The units are assembled in an end-to-end fashion and may be disassembled to take to a new location. Each unit comprises a horizontal header having hanging brackets on a top surface, a vertical support structure attached to the header and depending therefrom, a horizontal trough attached to the bottom of the vertical support structure and adapted to abut a top surface of the wall panels of a demountable movable wall system, and a plurality of cover panels attached to the support structure and positioned between the header and trough. Each of the cover panels has a horizontally elongated front elevational shape and the panels are detachably attached to the vertical support structure. One of the cover panels is adapted to interface with a building ventilation duct and has a ventilation grate to facilitate the flow of ventilation air to an interior of the building room.