Whereas the maintenance costs can vary. On the one hand, I can have a maintenance contract that changes the filters for me, then I can buy the filters on site, then you can get filters cheaply over the internet or you can even get cheap fabric by the meter. If, in addition to the filters in the system, you also equip the plate valves of the exhaust air inlets with filters, then the pipes don’t really get dirty either. Otherwise, of course, there is also a range for pipe cleaning. On the one hand, I can hire a company to do it or I pull a pull cord with a brush myself (like the chimney sweeps) through. Basically, it is purely a question of money whether you want to make the expensive purchase or simply install one or two exhaust fans and window rebate vents. The maintenance costs of a controlled residential ventilation system with heat recovery are easily offset by the energy savings. However, in my opinion, the energy savings are not enough for the acquisition costs to ever pay off.