thermal break, with no metal contact from inside to outside, to prevent heat transfer through the panel and prevent condensation on the outside. The inner wall protects the insulation from moisture damage and microbial growth. This type of construction makes the unit rigid, resistant to damage, provides increased sound dampening, and reduces air leakage and infiltration. Coated with polyuethane paint, it is corrosion resistant. These units have a a direct drive backwad curved plenum supply fans utilize rubber isolation mounts allows the units to be quieter, more efficient, and require less maintenance than belt driven fans. It utilizes R-410A scroll compressors, and a dimpled heat exchangerwith no internal turbulator, which can corrode over time. This type of heat exchanger provides energy efficient heat transfer. The different units have vaious capacities to meet the specific loads of the space it serves. They act as make-up air units (MUA) that only serve the corridors, trash rooms, and bathrooms. These units operate as part of the ventilation system by introducing outside air to these three types of zones as required by ASHRAE indoor-air quality codes. The units are designed to cool entering air temperature (EAT) at 95F in the summer and to heat EAT of 10F during the winter with a cooling and heating coil. However, the dwelling space of the residential apartment units utilizes natural ventilation. Code requirements says that if there are enough operable windows there is no requirement to mechanically introduce outside air. Integrated into the make-up air units are exhaust fans that run continuously so that bathrooms and trash rooms are constantly under negative pressure. This eliminates the requirement for small fans in each bathroom.