Energy recovery ventilators; fresh air preconditioners and energy saving preconditioners which recover energy exhausted out from conditioned air spaces and uses the recovered energy to precondition, i;e; heat or cool, fresh air being brought into conditioned spaces such as classrooms, homes, offices, conference rooms, restaurants, pubs, etc; treated fresh air units, also known as fresh air units, which are [ packages ] * packaged * air handling units incorporating energy recovery to ensure fresh air is preconditioned prior to entering conditioned spaces and preconditions the fresh air with the energy recovered from air conditioning systems; air handling units for treating fresh air, heat recovery wheels; energy recovery rotors, also known as heat wheels, for recovering wasted energy from the air exhausted from the conditioned spaces and used to precondition the fresh air being brought into the conditioned spaces to improve/maintain/enhance quality of air in conditioned spaces such as hotels, hospitals, commercial buildings, auditoriums and all other types of conditioned spaces; and structural parts and fittings for the aforementioned goods