Is a central ventilation system absolutely necessary?

The topic is very ideologically charged. If you ask 3 homeowners, you'll get 5 opinions.

So here is my opinion:
It is not necessary. We build with humidity-controlled supply air elements (from aereco) and exhaust extraction in the bathroom (upper floor) and guest WC (ground floor). And no, in winter you will not sit in cold draughts wearing a scarf and jacket. Our architect has been installing these things for many years. So far, there have been no complaints from the residents. No mold either. The investment costs are much lower than with a controlled residential ventilation system with supply and exhaust ducts in all rooms. The ongoing costs (heating the cold air with the described solution vs. electricity, maintenance and filters with controlled residential ventilation) will probably balance out.

Hello @klblb
I asked a question with this title:
Experiences with aereco supply air elements or similar.
I would like to hear from you because you have something like that in your house. (Here or PM)
What kind of supply air elements do you have installed?
Condensation in cold seasons?
How well are they soundproofed?
I tried to contact you via PM, unfortunately no success. I hope you even see my message

I'll just jump on the topic... Yesterday we were at a house seller (prefabricated wooden house) and he said you could do without a controlled residential ventilation system if you strictly adhere to their guidelines for window ventilation? To be honest, this is new to me since all sources or standard wooden house providers basically include controlled residential ventilation as part of the standard package? But I really can't believe that with just window ventilation?

Of course it works... how you ultimately ventilate doesn't matter... it's simply extremely uncomfortable because new buildings are built to be highly airtight by law and therefore need to be ventilated incredibly much. In our new development area, almost everyone who built without central controlled residential ventilation is now annoyed, and retrofitting is practically impossible, only the "second choice solution," i.e., decentralized fans.

And since it came up again here: insulation plays no role at all. Insulation is not responsible for the fact that there is no air exchange with the outside world. A house made only of bricks is nowadays just as airtight as a house made of sand-lime brick + [WDVS]. It has absolutely no impact on the indoor climate...

I'll join in on the topic... Yesterday we were at a house seller (wood prefab houses) and he said you could do without a controlled residential ventilation system if you consistently follow their guidelines for window ventilation? Honestly, that's new to me because basically all sources or standard wood house providers include the controlled residential ventilation system as part of the standard package? But I really can't believe that just relying on window ventilation?

I would simply advise against that. Manual ventilation, as required in such a new building, is much more effort than you might remember from childhood. You really have to ventilate 2 or 3 times every day. In summer, that might still be easy to manage, at least in my case, usually 2, 3 or more windows are tilted and there is a constant air exchange. But in winter, it's just horrible. I'm thinking about retrofitting a controlled residential ventilation system after all. The gain in comfort seems enormous to me by now. When I visit friends whose houses are equipped with such a system, you can clearly notice the difference. If I were to build new, then only with a controlled residential ventilation system.

Almost everyone in our new development area who built without a central controlled residential ventilation system is now annoyed, and retrofitting is practically not possible, only the "second choice solution," meaning decentralized fans.

What makes the decentralized solution the "second choice"? Many say that, but I haven't found any reasons for it yet?

I am more worried about potentially necessary future cleaning of the air ducts of the central variants... If they were proper round pipes, you could still say you pull rotating brushes through them, etc. But that gets difficult after the second bend at the latest. With all the flat and oval channels with ribbed design, it's basically impossible.

Sure, there are filters installed. But I have also serviced systems at work for a long time, and the same filter fleeces and flat-fold filters are installed as in the controlled residential ventilation systems. And inside the cabinets, after a few years, it looked like a mess. Only these could be opened and cleaned...

That's why I would be interested in some long-term studies? I once read that especially Sweden, which started very early with this, is moving away from it again. There must be reasons? Unfortunately, I just can't find that anymore...

With the decentralized variant, you wouldn't have these problems. And far fewer flow losses than the central variant. You just can't hide them as nicely. Or what else is seen as negative about it?

Please don't misunderstand, I don't want to praise either of the two, I don't know enough about them. But I would like to read independent long-term studies of both variants. If anyone knows something, I would be very grateful for a hint.

I had both and can only recommend the central variant to everyone. Decentralized has the following disadvantages:

- Loud due to fan noise
- Worsens sound insulation
- Poor heat recovery
- Air exchange only good with a very large number of devices
- Devices get dirty and many filters have to be changed
- Exterior facade is disfigured
- No central control

On the other hand, the argument about dirty pipes in central systems is long outdated. There are now systems that can be easily cleaned by oneself or specialized professional companies. In addition, even after 10 years, the pipes still look good. So this is just a misleading argument.

Central systems are thus preferable in every respect. There are only two arguments in favor of decentralized:

- Retrofit and partial use possible
- Significantly more cost-effective

Best regards