Abstract: An interdome enclosure system takes advantage of the latent heat of condensation for energy efficiency. The system includes, in combination with a humid environment, such as a heated pool and an outer enclosure housing the pool, an inner enclosure disposed within the outer enclosure and over the pool and a differntial fan operated heat exchanger for creating an atmospheric pressure within the space between the inner and outer enclosures which is positive relative to the atmospheric pressure within the inner enclosure. The heat exchanger includes a pair of conduits disposed in heat exchange relationship to one another. Assisted by an inlet fan, one conduit communicates dry, fresh cool air from the exterior of the outer enclosure into the space between the enclosures, while the other conduit, assisted by an exhaust fan, communicates moisture-laden, warm air from the inner enclosure directly to the exterior of the outer enclosure.