Apartments F–J each had a balanced mechanical
ventilation system with a heat recovery unit. The system
had two fans: one was for supplying outdoor air
and the other was for exhausting indoor air. The supply
diffusers mounted at the ceiling were connected to
the mechanical supply fan through the supply duct.
Exhaust diffusers were mounted at the ceiling, and
those were connected to the mechanical exhaust fan
through the return duct. The volume flow rate of supply
air was the same as the exhausted airflow rate, and
there was no recirculated air. The heat recovery unit
was used to transfer sensible and latent heat from
exhausted air to the supplied outdoor air. The exhaust
air was not mixed with the supply air in the heat recovery
unit.