Old and dirty filters lead to a pressure drop in the ventilation system and, as a result, the volume of fresh air inflow decreases, which worsens the indoor climate.
An old, dirty filter can contribute to the spread of mould in the ventilation system. (especially in humid climates), which can be a health hazard.
The new filter has the best air permeability levels and, as a result, savings can be made in electricity costs for the fan unit.