footprint, was experimentally characterized for passive waste heat recovery via air-to-air heat exchange in a typical Heating Ventilation & Air Conditioning (HVAC) ducting system. Experiments were designed to demonstrate the OHP's ability to utilize otherwise wasted thermal energy to pre-heat or pre-cool air for reducing building energy consumption. Results indicate that the OHP is fully-capable of operating while possessing a relatively long form factor (>1 m) and as a forced convection, air-to-air heat exchanger for waste heat recovery in HVAC systems.