Gas heating without solar thermal?

You will only be allowed to build a house in Germany if you comply with the Energy Saving Ordinance and the Renewable Energy Heat Act (in addition to other requirements, for example, the static calculations must meet the requirements). You are not allowed to just build whatever you want.

That is of course clear to me – in case it came across differently. For example, we also have special requirements regarding sound insulation.

Of course, that’s clear to me – in case it came across differently.

No, no, I just thought the statement helps to more clearly define the requirements according to KfW.

For example, we have additional special requirements regarding sound insulation.

By the way, I find that very interesting! From my very limited experience, this is a difficult area for many contractors. They somehow don’t know it ... Have fun designing the controlled residential ventilation, if desired .

By the way, I find that very interesting! From my very limited experience, this is a difficult area for many construction companies. They somehow don’t know about it ... Have fun installing the controlled residential ventilation, if desired .

How do you get from soundproofing to controlled residential ventilation? Probably the same way I do. I don’t want to have to open anything and still ensure air exchange. A central controlled residential ventilation system with heat recovery is very high on our list.

How do you get from soundproofing to controlled residential ventilation?

Because of the flow noises, which need to be minimized.

In this context (waiver of solar thermal energy), I came across the following:

§ 7 Replacement Measures

(1) The obligation under § 3 paragraph 1 or 2 is considered fulfilled if obligated parties

1. cover at least 50 percent of the heat and cooling energy demand
a) from systems for the use of waste heat pursuant to number V of the annex to this law or
b) from combined heat and power plants (CHP plants) pursuant to number VI of the annex to this law; § 5 paragraph 5 sentence 3, § 6 paragraph 1 sentence 1 and § 6 paragraph 2 apply accordingly,


Annex Requirements for the Use of Renewable Energies and Replacement Measures
V. Waste Heat
1. If waste heat is used by heat pumps, numbers III.1 and III.2 apply accordingly.
2. If waste heat is used by room air handling systems with heat recovery, this use is only considered a replacement measure under § 7 paragraph 1 number 1 letter a if
a) the heat recovery rate of the system is at least 70 percent and
b) the performance number, which is calculated from the ratio of the heat recovered and used from heat recovery to the electricity consumption for operating the room air handling system, is at least 10


Does this mean in simple terms: If you install a controlled residential ventilation system with heat recovery with a heat recovery rate of at least 70%, you are allowed to waive solar thermal energy. Is that correct?

Then we would have 2 levers to waive solar: 15% better building envelope or install correspondingly efficient controlled residential ventilation/heat recovery. The latter is already planned anyway, which ultimately means that we can waive solar without incurring additional costs.

However, I do not understand the addition about the performance number; can someone explain that to me in more detail?

Many thanks!

I will throw the chimney into the mix depending on the federal state (for me BW):
Replacement measure for log wood combustion applies if

- chimney has an efficiency greater than 80%
- at least 30% of the living area is predominantly heated with it