PHANTOM represents the latest generation of ventilation units with heat recovery. It is responsible for supply of fresh air to the inside of a building and exhaust of used air to the outside. This is achieved by fans and energy is recovered in a plastic counter-flow heat exchanger. A recuperator constitutes the most important element of each ventilation system, in particular in low-energy and passive housing development. Correct selection of such equipment has direct impact on residents’ comfort and savings during the whole period of operation.