Building a single-family house in NRW

Dreamcatcher, please inform yourself properly ... Cleaning systems have existed for a decade. ... Alternative facts à la Trump? Man, man, man.. so much simplicity is irritating...

I prefer to inform myself a bit before following the opinion of a single, highly controversial person.

Hello Grym, thank you for taking the time to respond again. If I follow your logic, everything that has existed on the market for over a decade is proven and error-free? Well, then I conclude that since there have been nuclear power plants for over 60 years, the increased cancer rate around the Krümmel nuclear power plant (for 25 years) is by no means attributable to nuclear power? So everything that was not identified as harmful within the first 10 years is not harmful at all? Grünenthal & Co. will be very pleased about that.

My suggestion: Enjoy your controlled residential ventilation and the fresh air in the house. I just wanted to give the other forum members who have not yet bought a controlled residential ventilation system for > 10,000 EUR a food for thought. They can consider it quite democratically or not. This was not meant badly towards those who chose it in the past and it is also not an exclusion criterion to install such a system.

Hm... Your words confuse me, but you are certainly right, in this sense, "Thy will be done, on earth as it is in heaven.", who could still doubt your truths???

It’s not definite, but the chances are drastically higher. And if with 2x airing you just barely don’t have any mold, that’s okay. Have you checked behind all the furniture etc. and inspected the corners?

No, not just barely, but not at all, not at all. Man, man, better check under your hat if you don’t find some mold there.

We were once in a private house of a home seller who also aired 2-3 times a day, always with the extractor hood and ventilation, and still had mold problems. It’s a bit of a gamble, everyone has to decide how they want to handle it..

Oh, the famous isolated case that has to serve as proof. Maybe he didn’t air at all or there was another source for the excess moisture? Who knows. Certainly not you.

And of course nowadays every expert basically advises you to have a controlled residential ventilation system. Architects, engineers, energy consultants. Controlled residential ventilation is only still often skipped for cost reasons.

Oh, ALL of them. So you know the opinion of all experts. Amazing. I’m getting tired of this. It’s like arguing with believers.. Don’t get me wrong, controlled residential ventilation is okay. Just not a must...

Your comments are on the level of "walls breathe" and I currently lack the time and inclination to enlighten you about this primal slime.

There are pros and cons, but what you write is rubbish. Definitely, a controlled residential ventilation system costs a lot of money, and building a house also involves compromises. You have to weigh that for yourself. The risk of mold in a tightly sealed house always exists. Cleaning, if even necessary, is easy with a controlled residential ventilation system. You can do it every 10 years for peace of mind. As long as the filter (also use exhaust air filters!) is changed quarterly and the system runs 24/7, the air in the ducts is practically cleanroom atmosphere. This also applies to kitchen exhaust air!

The load of CO2, formaldehyde, VOCs, etc. in unventilated rooms is already noticeable after 2 hours without ventilation. Likewise, the controlled residential ventilation system filters fine dust from the outdoor air.

What does this KFW 55 or 70 actually mean and is it a must?

(The "must" has already been explained)

The KFW is the "Kreditanstalt für Wiederaufbau" (referring to "after the Second World War," as the institution was created in connection with the "Marshall Plan"). "70," "55," and "40" are percentages (of a previous consumption value = index 100), and in these three levels, more savings are more heavily subsidized. KfW70 means an energy consumption reduction of 30 (so down to 70) percent of the reference value. As far as I know, this is no longer subsidized because the Energy Saving Ordinance (EnergieEinsparverordnung) must be met anyway at the same level. KfW40 saves 60% (so only 40 remain). The ratio between "effort to achieve the target" and "subsidies that make the dream home affordable for the builder" is probably most attractive for KfW55 to house providers, which is why significantly more products are tailored to KfW55 than to KfW40. As mentioned, KfW70 has become de facto unattractive or obsolete.

The KfW is - simply put - a federal central bank for subsidies.

The risk of mold in a sealed house is always there.

Aha, so at least there is some agreement on that.

The concentration of CO2, formaldehyde, VOCs, etc. in unventilated rooms is clearly noticeable after just 2 hours without airing. Likewise, the controlled residential ventilation filters fine dust from the outside air.

That is absolute overkill, but for some people this technicizing and automating is a hobby.

Blind control please without technical devilry, but when replacing analog window ventilation it is helpful. I don’t have to understand everything.

Cleaning, if necessary at all, is easy with controlled residential ventilation. You can do it every 10 years for peace of mind. Provided the filter (also use exhaust air filters!) is replaced quarterly and the system runs 24/7, the pipes have almost cleanroom atmosphere.

I clean my windows much more often than every ten years, and a fly screen in high summer is enough air filter for me.