An example refrigeration system includes an indoor fluid loop, an outdoor fluid loop, and a heat exchanger assembly. The indoor fluid loop circulates a first working fluid. The outdoor fluid loop circulates a second working fluid that is different from the first working fluid and is separated from the indoor fluid loop by a wall of a structure. The heat exchanger assembly is mounted within the wall of the structure. The heat exchanger assembly includes a heat exchanger and a housing, where the heat exchanger is disposed within an internal space defined by the housing. The housing supports the heat exchanger within the internal space and is mounted to a structure of the wall.