Decentralized vs. Central Controlled Residential Ventilation? Points for KfW House Calculation

...but would I drop from a KfW 70 house to KfW 55 with a controlled residential ventilation system including heat recovery, or does that not play a role?

The efficiency status is defined by two parameters that must be met: HT´ (W/m²K) - indicates the permissible transmission heat losses (building envelope) and qp´´ (kWh/m²a) - permissible specific primary energy demand. Both values must be complied with! qp´´ is influenced by both heat losses and gains, as well as the system technology. The controlled residential ventilation/heat recovery has no effect on HT´, but it does affect qp´´. This value therefore improves. In each individual case, it must be checked which of the two values, or whether both, are not sufficient for KfW EH 55. In the present case, qp´´ is presumably not the stumbling block. Usually, depending on the chosen system technology, the HT´ value is the "problem child." Here, it is often only possible to meet the requirement with considerable effort. An efficiency status according to KfW requirements only characterizes qualitatively the primary energy condition of a building (building envelope and system technology). However, a statement/assessment regarding economic efficiency is by no means possible/given. A KfW EH 70 can overall be more economical than a certified PH. The pure chase after so-called "gifts" often leads to the wrong overall result.

v.g.

Ah,

all clear, thanks for your explanations. That helps me understand it a bit. My main concern is also that I don’t pay twice for the same thing.

By that I mean, paying around ~5,500EURO once for the Kfw 70 standard and then another ~9,000EURO for the [Kontrollierte-Wohnraumlüftung+Wärmerückgewinnung]. In hindsight, with the [Kontrollierte-Wohnraumlüftung + Wärmerückgewinnung] and e.g. triple glazing, I would have also met the KfW 70 standard and only paid "around" 11,500EURO instead of 14,500EURO.

Happy Easter to all.

Hello €uro,

Whether a PH makes sense is another matter.

We probably both see it this way, along with a handful of other people; from 2021 this question unfortunately will no longer arise. I am already curious today about what the individual solution approaches will look like, because a PH cannot be realized on every property.

This possibility basically exists, it is just not taken advantage of, presumably because it is not so convenient. It helps the builder less or even harms them, but sellers have no reason to complain.

This possibility certainly exists in principle; you – just like me – know, however, that it is hardly used, measured against the statistical new construction volume. For a layperson, a house seller is often equated with the aura of a white coat, especially when rhetorically well trained; accordingly, the houses are planned and sold. In my opinion, this is the first problem. The next would then be the Internet, which – as a reaction to trained sellers – turns a layperson into an unpleasant conversational partner. Not because they are enlightened – that would be desirable – but because half-knowledge mixes with hearsay. And ultimately every service costs money and the new kitchen is always more important to the builder than reasonable advice or TGA planning.

The majority of sellers will also not complain; I would bet that most of them would not even know what we are discussing here.

Happy Easter