Abstract: A rooftop air conditioning unit for conditioning air in a conditioned space is provided with a rotary regenerative exchanger where sensible and latent heat transfer occur between exhaust air and fresh air with the use of a rotary regenerative exchanger. The exchanger is secured to the housing of the unit in front of a side opening adjacent the air circuit thereof. The position of the exchanger avoids a modification in the conditioned air ductwork of the conditioned space and allows sharing the same roof reinforcement structure with the original unit.