Abstract: A ventilation and dehumidification system for ventilating fresh air to a conditioned space. The system is comprised of a desiccant wheel for dehumidifying incoming air by exchanging moisture from an inflow current of air with an outflow current of air. The desiccant wheel is both regenerated and defrosted by a regenerative heater which is placed to heat the outflow current of air before the outflow current passes through the desiccant wheel. The system includes blowers in order to motivate the inflow and outflow currents of air. The system may also include heat recovery means such as a heat transfer wheel or a motionless heat transfer core. The blowers can be arranged so as to create an air pressure differential between the inflow chamber and the outflow chamber so that any leakage of air between the two chambers will occur from the inflow chamber to the outflow chamber.