an improved apparatus for conditioning the temperature of the air in a substantially confined space , such as a room , is disclosed . the conditioning system is complete and integrated in a portable unit suitable for insertion in a wall opening , such as a window . the operative elements are divided between two separate enclosures , each attached to a common structure , the support capable of resting on the window sill , with one such enclosure on each side of the wall . at least the heat exchanger conditioning room air is disposed in the enclosure in the room side of the wall . at least the compressor is segregated in the other enclosure , on the other side of the wall of the conditioned space . and both enclosures sit substantially below the sill line . obstruction of the window opening is much reduced over prior art units . installation is easier and safer . and the segregation of the compressor , which can be improved by sound and vibration dampening treatments , drastically reduces the noise level in the room produced by the system &# 39 ; s operation .