This is most effective in a suspended or “floating” ceiling where there is room to accommodate the unit. Since cold air falls towards the floor, the ceiling mounting provides exceptional coverage and, provided the fans are powerful enough, a ceiling cassette AC unit can cover a fairly large room. Being in the ceiling also means that the units are out of the way. It is strongly recommended that you contact an expert prior to purchasing the unit as if the incorrect design is chosen or if it is improperly installed, operating costs could be high.