Controlled residential ventilation with heat recovery instead of solar thermal energy?

Yes, I would be interested in that too

It's a pity that no feedback has come so far; the answers would also be highly interesting for many others, even if only as an indication.

My own amateur calculation using the Energy Saving Ordinance Excel tool from the University of Kassel showed that with gas + controlled residential ventilation without solar, even with better insulation (KfW55 level) and airtightness testing at the Ht-value (0.24), we are indeed more than 15% below the Energy Saving Ordinance 2016 requirement (0.35), but not in terms of the annual primary energy demand.


The Renewable Energy Heat Act requires, as a valid substitute measure, an annual primary energy demand 15% lower than the Energy Saving Ordinance 2016 and an insulation value 15% better than the Energy Saving Ordinance 2016.



According to the Energy Saving Ordinance 2016, we were allowed a maximum annual primary energy demand of 49.38 kWh/(m²a). However, the house only reached 52.85 kWh/(m²a). That means even the Energy Saving Ordinance 2016 would not be fulfilled.
The Energy Saving Ordinance 2014 with a maximum value of 65.84 kWh/(m²a) would have been achieved, but that no longer counts. Then it would even have been enough as a substitute measure (85% = 55.96 kWh/(m²a)) without solar.

If a detailed thermal bridge calculation is done, our house (depending on the result of this calculation!) would reach a speculative 48.40 kWh/(m²a), and only then would we just fall within the Energy Saving Ordinance 2016.


So I see absolutely no possibility based on my amateur inputs in the Excel calculator to dispense with solar since the Energy Saving Ordinance 2016 under the Renewable Energy Heat Act if you want to use gas.

Our energy consultant is currently calculating but has not really encouraged us for this.



All the more interesting would be the data/calculations of other builders or the contact details of their energy consultants

Wait and see what the energy consultant says. He will know one or the other trick. If I look at my thermal insulation certificate and see all the factors that count ... e.g. auxiliary energy (circulation present yes/no), night setback, solar gains ... The ventilation system also has a huge impact on the energy demand through heat recovery. A photovoltaic system also has a positive effect, if that would be an option.

Masonry:
17.5 cm aerated concrete/ Ytong
16 cm 2-layer mineral fiber mat
3 cm construction joint
11.5 cm facing brick

U value: 0.15

Roof or ceiling:
Mineral fiber - 20 cm and 10 cm - WLG 035

U value: 0.12

So from my point of view standard.

Masonry:
17.5 cm aerated concrete/ Ytong
16 cm 2-layer mineral fiber mat
3 cm working joint
11.5 cm facing bricks

U value: 0.15

Roof or ceiling:
Mineral fiber - 20 cm and 10 cm - WLG 035

U value: 0.12

So from my point of view, standard.

Our wall construction looks exactly the same.
In the roof or beam layer, we have 24 cm WLG 035.

Therefore, we can also do without the solar system and instead install a central ventilation system.

We wanted to combine a gas condensing boiler with a controlled residential ventilation system with heat recovery. Our architect says that is not sufficient to meet the requirements. So, there will be the unpopular photovoltaic system again, along with the issue of [EÜR] at the tax office. This time with a storage unit.

A photovoltaic system has absolutely no impact on the primary energy demand. You probably mean solar thermal. I would have this calculated in advance instead of blindly trusting the architect. In my opinion, this should very well be possible if you invest a bit more in insulation additionally. Overall, this results in a much more sensible package, since solar thermal regularly is not cost-effective and, unlike the controlled residential ventilation, does not bring any further advantages.