Ventilation and exhaust: Hygienic problems after 5-6 years

Our electrician thinks that in a few years, ventilation systems will only be allowed to be installed with heat recovery. Ours is decentralized. Purely a matter of taste, I would also say on this topic.

From what I have read in other threads, the central ventilation system apparently only comes with heat recovery, and only the decentralized one depending on preferences with or without? Is that correct? With funding from KFW, for example in an FKW 55 house, you can’t avoid the central system including heat recovery anyway, from what I have been able to find out so far.

Well – to my knowledge, decentralized ventilation systems only come with heat recovery. The others are simply exhaust fans – they only extract the used/moist air (e.g., from bathrooms) out of the house. Such exhaust fans can also be used for house ventilation. In that case, the intake of air occurs through negative pressure via, for example, window frame air slots or similar. Then only cold air would be sucked in accordingly. This does NOT count as a ventilation system for ME personally.

Decentralized ventilation systems are basically fans that change the direction of the air in cycles (e.g., draw in fresh air for 75 seconds and then blow out for 75 seconds). In this process, the fans usually operate in pairs (one extracts air, the other provides intake). The expelled air passes through a heat stone, which stores a good portion of the heat and then releases the stored heat again when fresh air is drawn in. Each fan has a dust filter (optionally pollen filter), which should be cleaned (replaced) regularly. 10 dust filters = approx. 30 euros. In damp rooms, it makes sense to install a few exhaust fans as well, which start up as needed (high humidity) and switch off again after a few minutes (when the humidity has dropped). These operate independently of the decentralized system.

Well - to my knowledge, decentralized ventilation systems only exist with heat recovery. The others are simply exhaust fans - they only pull used/humid air (e.g. from bathrooms) out of the house. Such exhaust fans can also be used for house ventilation. Then, the air supply occurs through negative pressure via, for example, window rebate air slots or similar. In that case, only cold air would be drawn in accordingly. This, for ME personally, does not count as ventilation systems.

Decentralized ventilation systems are basically fans that alternate the direction of airflow in cycles (e.g. draw in fresh air for 75 seconds and then blow out for 75 seconds). In this process, the fans usually operate in pairs (one pulls out, the other ensures supply). The exhausted air is passed through a heat stone, which stores a large part of the heat and then releases the stored heat again when fresh air is drawn in. Each fan has a dust filter (optionally a pollen filter) which should be cleaned (replaced) regularly. 10 dust filters = approx. 30 euros. In damp rooms, it makes sense to install a few exhaust fans that switch on when needed (high humidity) and switch off again after a few minutes (when humidity has decreased). These operate independently of the decentralized system.

Oh, okay, I thought there were only central ones with heat recovery. Seen like that, the decentralized ones also sound very interesting.

With the central ones, as already said, there is a central point, and with the decentralized ones, the fans are always in the respective room. It is probably again, as so often, a matter of preference whether it bothers one visually from outside or inside. For me, what I still do not know would be the noise level as the bigger issue, whether you choose central or decentralized if no heat recovery is needed. In terms of maintenance, the decentralized ones are definitely simpler and easier.

More likely the central ones, where you only replace two filters - at most an extra paper filter in the exhaust ducts. In a new building, I would always choose the central version - solely because of continuous air exchange, lower electricity costs, noise levels, and appearance (also on the outside).

I was not aware that electricity costs are lower with a central solution or that they operate more quietly. You also have continuous exchange with a decentralized solution. I cannot say how high the maintenance costs of the individual variants are. Maybe there is someone here who has been in the house for at least three years and can report. Like the type of heating, the decision whether central or decentralized is, in my opinion, dependent on personal preference.

I currently change both filters every 6 months - it costs me 30 euros per change. I would say it works more quietly, since the ventilation unit is located away from living spaces and you can’t hear anything from the ventilation (assuming correct settings). With decentralized ventilation, you have the fan directly in the room - it certainly won’t be a loud noise maker, but I doubt you wouldn’t hear anything at all.

Less a matter of taste – more of the wallet or what one wants to spend (also with heating).