KFW70 with gas-solar heating

From ... to ... depending on the size of the house. When in doubt, for what is sold to you Our (decentralized), calculated for a small house maybe around 5.5 k€; with us 5 k€ material + installation and wiring - so about 7.5 k€ I would estimate, a central one rather about 8-12 k€ (?)

Not necessary, but only if the ventilation intervals can be maintained...

around 10,000, but jumps of 30% up and down are possible... depending on the system and how it is built, etc.

A controlled residential ventilation system is not strictly required for a single-family home, Kfw 70 can definitely be achieved in other ways, but would manual ventilation be an alternative, i.e., opening windows briefly to let warm air out and cold air in during winter?

And why not Kfw70? The year after next it will be standard. The house can hold its own better in the sales market, even after 20 years.

And why not Kfw70? In the year after next, it will be standard. The house can better assert itself on the sales market, even after 20 years.

mh, you hear that often, but I consider the argument untenable. What about the houses that were built 7 years ago according to KFW70 or 60 or similar? Today, they no longer comply with the Energy Saving Ordinance.

And in 20 years, no one will know what crazy ideas the government/EU will have come up with (the insulation craze will soon reach its natural end) – no one will care anymore that the house was built under an Energy Saving Ordinance 20 years ago.

Or how do you see it?

I happen to build according to KFW – we didn’t plan for it, don’t over-insulate either, still achieve KFW56 and also include the 50,000 euros at favorable conditions.

After subsidies, we pay about 5,800 euros total for our Helios central system with enthalpy exchanger including all materials and planning – installation is done by us. And that is already a rather high-quality and large ventilation system.

The first offer from the plumber for a significantly smaller and worse system amounted to almost 12,000 euros...

I think the insulation will rather increase... how do you come to the conclusion that it will stop soon?

Because you can't insulate infinitely - have you ever seen an insulation curve? It flattens out significantly at the end - you won't recoup the savings compared to the investments within 20 years.

For example, we insulate our sand-lime brick only with 14 cm - I think that with the anchors currently a bit more than 20 cm is possible. However, this means the house has to "grow" accordingly, the materials are much more expensive, and the effect - well, try calculating it with the U-value calculator. Also regarding WLG 035 and WLG 024 - the effect isn't as huge as one might initially suspect.

Next, in my opinion, the ecological effect of a construction project will come into play - then the solid house builders will have a problem and timber (frame) houses will be promoted/advertised.