In a leaky house the air is exchanged naturally, which it must be to make the house habitable. In an airtight house, the same effect is provided artificially via an energy efficient ventilation system with a heat exchanger. The ventilation system forces the stale air out of the house via the heat exchanger, in which the incoming air is warmed up by taking energy from the outgoing air. Bjorn, the architect and project manager, rolling on tape.
Marian, the building contractor, cutting tape.
Zuzana, the architect, cutting tape.