KfW 55 - Ventilation system yes/no? - Experiences

Another point: If your GU installs Controlled Residential Ventilation in less than 10% of the houses, then I would probably also be somewhat suspicious of how well it is implemented. For the companies that have been installing Controlled Residential Ventilation as a standard for a long time, I have a bit more confidence that the overall system is mature.

The way you write, you have already made your decision for yourself. That's okay.

I had both for years and decided for myself never again without [Kontrollierte-Wohnraumlüftung]. It's still okay in summer, but not in winter.

Why shouldn't I build a KfW 55 house??? Again... I get a repayment grant of 18k with an additional cost of about 5k. WHY should I build a KfW 70 house????

It's not just that you are critical of the ventilation system, you are also not exactly convinced by heat pumps. And I wonder how you want to achieve the Efficiency House 55 standard. My personal recommendation for you would be a classic gas condensing boiler with solar thermal support, window rebate ventilation, and underfloor heating (which, however, is already designed to be heat pump compatible, i.e. low flow temperature). Whether you can build an Efficiency House 55 with this, I don't know. I would ask your general contractor about that. I would also be interested to know what is included in your "KFW 55" package for 4 - 7k or how the system technology looks there.

I would then waive the repayment grant or the profit you want to make; although 13k is a lot of money, over the lifetime of the house or the loan period it becomes negligible, and personally, it would not be worth it to me to give up my own conviction for that.

For the sake of formality, it should be said that my recommendation for you in no way represents my convictions about new construction in the current times.

Fortunately, values are measurable and figures verifiable. I don't need a contractor who writes in his contract that regular ventilation prevents mold.

Whether it's the CO2 level in the room or the heat loss due to ventilation.
Obviously, there isn't a huge leap between kfw55 and 70, but just compare the heating costs of houses from the 70s or 80s, where usually not all rooms are heated, or heating is supplemented with a fireplace.

We have 4-5 rooms per floor in the house. If I had to walk through the house every time to ventilate them, oh dear...
Of course, he would prefer to build without it.

I also don't know any general contractor who likes to install central systems. Too high potential for errors during shell construction installation and it squeezes their overall margin. But apartment buildings are nowadays equipped almost 100%, because landlords don't want trouble with mold.

There is no simpler decision in construction than controlled residential ventilation yes or no. There are clear decision parameters for that. It is also not a matter of belief, as my predecessor says, all of that is measurable.

With a controlled residential ventilation system, it is like with many things. If you never had it, you don't miss it and cannot explain the benefits. Once you have enjoyed the constantly fresh air, you don't want to go without it anymore (at least I don't know anyone with a controlled residential ventilation system who ever wants to be without it again...).