ᐅ Is a Central Ventilation System Really Necessary?

klblb schrieb:
This topic is quite sensitive. If you ask three homeowners, you’ll get five opinions.

So here is my view:
It’s not necessary. We use humidity-controlled air supply vents (from aereco) and exhaust extraction in the bathroom (upper floor) and guest toilet (ground floor). And no, in winter you won’t be sitting in cold drafts with a scarf and jacket. Our architect has been installing these for many years. So far, there have been no complaints from the occupants. No mold either. The initial costs are much lower than with a mechanical ventilation system with supply and exhaust ducts in all rooms. The ongoing costs (heating the cold air in this solution versus electricity, maintenance, and filters for mechanical ventilation) will probably balance out.

Hello @klblb
I posted a question with this title:
Experiences with aereco air supply vents or similar
I would like to hear from you because you have something like this in your house. (Here or by private message)
What type of air supply vents did you install?
Is there any condensation in the cold seasons?
How well is the noise insulation?
I tried to contact you by private message, but unfortunately without success. I hope you see my message at all.

I’ll jump in on this topic... Yesterday we visited a house seller (prefabricated wooden house), and they said that you could do without a mechanical ventilation system with heat recovery if you strictly follow their guidelines for window ventilation. To be honest, this is new to me because all sources and standard wooden house providers basically include mechanical ventilation with heat recovery as part of their standard package. But I really can’t believe that window ventilation alone would be sufficient.

Of course it’s possible… how you ultimately ventilate doesn’t matter. It’s just highly uncomfortable because newly built homes are legally required to be extremely airtight and therefore need to be ventilated very thoroughly. In our new development area, almost everyone who built without a central controlled ventilation system is now frustrated, and retrofitting is practically impossible—only the "second best solution," meaning decentralized fans, is an option.

And since it came up again here: Insulation doesn’t play any role at all. Insulation is not responsible for preventing any air exchange with the outside. A house built solely from bricks today is just as airtight as a house made of sand-lime bricks plus external thermal insulation composite system (ETICS). This has absolutely no effect on the indoor climate…

lesmue79 schrieb:
I’ll just join this topic... Yesterday we visited a house seller (prefabricated wooden house), and they said you could do without a mechanical ventilation system with heat recovery if you strictly follow their recommendations for window ventilation? Honestly, this is new to me since all sources or standard wooden house suppliers basically include mechanical ventilation with heat recovery as part of their standard package? But I really can’t believe that just relying on window ventilation would be enough?

I would simply advise against that. Manual ventilation, as required in a new build, is much more effort than what people might remember from childhood. You really have to ventilate two or three times every day. In summer, this may still be easy to manage. At my place, I usually keep two, three, or even more windows slightly open, ensuring constant air exchange. But in winter, it’s just miserable. I’m considering retrofitting a mechanical ventilation system with heat recovery. The increase in comfort seems enormous to me now. Whenever I visit friends who have such a system installed in their house, you can clearly notice the difference.

If I were building a new house, it would definitely be with a mechanical ventilation system with heat recovery.

Tego12 schrieb:
In our new development area, almost everyone who built without a centralized mechanical ventilation with heat recovery system is now frustrated, and retrofitting is practically not possible—only the "second-best solution," meaning decentralized units.

What exactly makes the decentralized solution the "second-best" option? Many people say this, but I haven’t found clear reasons yet.

I’m more concerned about the potential need to clean the ducts in centralized systems. If they were proper round ducts, you could run rotating brushes or similar tools through them, although that becomes difficult after the second bend at the latest. But with all the flat and oval ducts with ribbed designs, that’s basically impossible.

Of course, filters are installed. But I’ve maintained long ventilation systems at work, and they use the same filter mats and flat-panel filters as in mechanical ventilation with heat recovery. After a few years, the filter housings looked really dirty—but at least you could open and clean them.

That’s why I’m interested in some long-term studies on this topic. I once read that Sweden, which adopted these systems early on, is now moving away from them again. There must be reasons for that, but unfortunately, I haven’t been able to find more about it.

With the decentralized approach, you wouldn’t have these problems, and there are far fewer pressure losses compared to the centralized system. The only downside is that you can’t hide the units as neatly. Is there anything else negative about them?

Please don’t get me wrong—I’m not trying to praise one or the other solution, as I don’t have enough expertise. But I would like to read some independent long-term studies comparing both options. If anyone knows of any, I’d be very grateful for a reference.

I have experience with both systems and can only recommend the central ventilation variant. Decentralized systems have the following disadvantages:

- Noisy due to fan sounds
- Reduces sound insulation
- Poor heat recovery
- Effective air exchange only with a large number of units
- Units get dirty and require frequent filter changes
- Spoils the exterior facade
- No central control

The argument about dirty ducts in central systems is outdated. Nowadays, there are systems that can be easily cleaned by yourself or by specialized professionals. In addition, even after 10 years, the ducts still look good. So, this is just a misleading argument.

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

- Can be retrofitted and used partially
- Significantly cheaper

Good luck