Ventilation efficiencies of wall or window mounted residential air-to-air heat exchangers.

Describes a series of experiments to determine the ventilation performance of 2 different models of wall or window mounted heat exchangers. Determines their nominal efficiency by the measurement of tracer gas decay rates at several indoor locations. Notes significantly higher local ventilation efficiencies in rooms where heat exchangers are operating. Some preliminary tests indicate that internal leakage between the air streams contribute significantly to the ventilation inefficiency of these systems.