KFW 40 (Energy Saving Ordinance 2014) without ventilation - Retrofit options

Hello everyone,

beforehand - I have dealt a lot with the topic, I know the pros and cons, etc. It's not about a fundamental discussion (I have certainly read about 40 pages on this topic here in the forum).

Fact:
1. We are very interested in a property that is offered by the developer as follows: construction according to Kfw Efficiency House 70 - standard (according to Energy Saving Ordinance 2014)
2. no ventilation
3. The construction is very far advanced (currently the underfloor heating is being installed)

Questions:
1. I always thought Kfw 70 and Energy Saving Ordinance 2014 are two different standards? Isn't Kfw 70 now according to Energy Saving Ordinance 2016? Or am I misunderstanding something.
2. If I were to plan new, I would probably install ventilation. Since there are pros & cons, it seems to me, however, that it is not a no-go that none is installed. It's just associated with more caution & effort. Is there anything based on this that I should definitely ask about (ventilation concept, air exchange rate, etc.)? / Does something have to be mandatorily calculated and designed, or does the architect do that to the best of their knowledge and belief?
3. Since the construction is so far advanced, I can no longer retrofit mechanical ventilation. Should I get problems after some time nevertheless. What options do I have without having to tear apart the whole (new) house? Of course, it's clear that it then costs a few thousand euros...

Regards Marco

1. As far as I know, kfw-70 no longer exists (but I could be wrong)

2. You would have to inquire about and adhere to the ventilation intervals

3. You can install a decentralized system at any time, even now... it's best to have the cables for it laid into the walls already now

1. I think construction started just before April 2016 (it's almost finished now) and that's why it is still advertised as KfW 70. Otherwise, I agree with you.

2. Ok, I will do that. Does that mean there has to be a calculation for it?

3. The house is already painted on the outside & the underfloor heating is being installed inside. I'm afraid it's too late to have anything additionally installed in the walls, isn't it?

Whether you can still get cables in now depends entirely on the construction method and the sequence of the trades...