ᐅ Controlled residential ventilation with heat recovery — a confusing topic?

Hello dear forum members,

We are—more or less—at the stage of choosing the general contractor, and now the question of installing a controlled mechanical ventilation system with heat recovery has come up again, even though we had initially decided against it for ourselves.

An appointment with a building expert from the Homeowner Protection Association really challenged my views and reopened the question of whether we need such a system at all.

Just to preempt some of the typical forum assumptions: yes, I have spent a day and a half on this forum and elsewhere absorbing information like crazy. I’m probably wiser, but still not ready to make a decision. It can’t be that I have to roll dice or flip a coin here.

I would really be interested in concrete arguments for why one might be able to do without such a system. For a controlled mechanical ventilation system with heat recovery (Pedotherm / Vaillant), we would have to pay nearly 10,000 euros. That’s quite a chunk. The general contractor did not push for it but clearly said it is not absolutely necessary (if you ventilate really well). However, in our case, there is practically no one home between about 7 a.m. and 4 p.m. That would be rather disadvantageous, especially in the first years of the new build, because window ventilation would naturally be reduced during those hours.

Man, this is quite frustrating when you feel so uncertain. Could you please help provide some reassurance?

Good morning,

Voki1 schrieb:

Just to prevent any (usual forum) assumptions: yes, I have now spent one and a half days on this forum and have absorbed information like crazy elsewhere, too. I might be wiser now, but somehow still not ready to decide. It can’t be that I have to roll dice or flip a coin here.

https://www.hausbau-forum.de/threads/Lüftung-nur-im-Fertighaus-holzstaender-mit-WDVS-oder-auch-im-Massivhaus.10624/

Preventing didn’t help


No one can make this decision for you, just as no one can argue definitively for or against a controlled residential ventilation system with heat recovery. Therefore, your gut feeling and budget are essential since this is primarily a personal decision. By the way, the Bauherren-Schutzbund – what the independent experts working under this umbrella sometimes say – should always be taken with caution. Quite a few of them overshoot the mark, others don’t find it at all, and some don’t know the way.

Voki1 schrieb:

The general contractor didn’t push but clearly said that it’s not absolutely necessary (if one really ventilates properly). However, at our place, practically no one is home between about 7 a.m. and 4 p.m. In the first few years, this (new build) would not be ideal, since natural (shock) ventilation would obviously not take place during that time.

From my professional perspective, this is a reasonable statement because houses are becoming tighter (and have to be). With solid construction without external thermal insulation composite systems (ETICS / WDVS), ventilation "can" work without mechanical systems, but it is not necessarily required; with a new build that includes ETICS, this question, in my opinion, does not even arise. Another interesting question is whether it "must" be a fully controlled ventilation system or if a decentralized system "can" also be an option (warning... controversial discussions will follow) – in other words, whether a compromise between work schedule and ventilation can be reached. Especially since decentralized systems also offer some advantages and generally require about half the investment.

Voki1 schrieb:

Man, man, man, it’s quite annoying when you’re this uncertain. Can you contribute to helping me feel more certain?

No

Regards, Bauexperte

We are building with solid construction and a brick facade, so without external thermal insulation composite system (ETICS). This way, our house can still "breathe" somewhat, which was important to us. Additionally, for budget reasons, we decided against a mechanical ventilation system, even though we are not home during the day (at least for another year). We believe proper occasional ventilation in the morning and evening will be sufficient. Ultimately, no one can make this decision for you.

You have to make the decision entirely on your own. We are building with solid masonry without external thermal insulation composite systems (ETICS) using 36.5 Poroton blocks and without mechanical ventilation with heat recovery. However, we decided to install decentralized ventilation with humidity control in the bathrooms and utility room. These three ventilation units cost us around 1000 euros.

We are still considering a decentralized system.
@Manu: Why in the utility room? Is laundry done there? I’m wondering where else we might need a decentralized system.

Yes, we have the utility room and the technical room separated. The washing machine and dryer will be placed in the utility room, and occasionally the drying rack as well. Therefore, we have installed (and are still installing) a decentralized ventilation system in all areas where there is higher humidity.