energy-efficient house = a house which consumes significantly fewer heating resources than a conventional house, due to the construction technology and materials used;
tightness = the property of the room or building to be perfectly closed, therefore avoiding the dissipation of energy and humidity through cracks and holes in the walls (such as those around cables or pipes);
passive window / window with increased efficiency = window with a very high isolation capacity, which blocks the heat transfer and loss almost entirely;
thermal bridge = area of a building where the heat transfer easily takes place, allowing for large heat losses;;
ventilation system with heat recovery = ventilation system that allows heat recovery of the interior space, while at the same time ensuring constant air freshening and filtering of the dust and allergens;