Which heating system? Air heat pump / Gas / Geothermal

Hello,

I don’t understand the second part of the sentence :-(. Also in the sense of "additionally"? Isn’t it enough to reduce the primary energy demand to 85%?

I mean exactly what I wrote: "15% reduction of the primary energy demand and at the same time at least 15% better building envelope". The Renewable Energy Heat Act does not provide for either/or in this case, although there are many ways to Rome (can lead). By the way, the term primary energy refers to the type and amount of energy taken from the utilized natural sources.

Now I’m confused again. What is a better building envelope? How is "better" evaluated if not by the primary energy demand of the house? In other words: measures to reduce heat losses (e.g. at the envelope) reduce the primary energy demand to 85%: Done, the builder is allowed to install a gas condensing boiler without heat pump, without solar thermal, without photovoltaics.

You can – as an alternative to the use of renewable energies – increase the energy efficiency of your building by, for example, better insulating the building envelope, ventilating with heat recovery, or implementing other measures recognized by the Renewable Energy Heat Act (which mandates the use of renewable energies in new buildings). Specifically, this means: The building must undercut the requirements of the applicable Energy Saving Ordinance by at least 15%. Proof is provided by an energy performance certificate according to the Energy Saving Ordinance.

The building envelope does not consist "only" of stones; roof, insulation, façade, and windows also belong to it. When the 15% rule is applied, it always means that there must be a mix of different measures. These affect both the primary energy demand (which type and amount of energy), as well as the building envelope (filled stone, better insulation, better windows, etc.). As always, there are exceptions: simply connecting to a district heating network whose heat comes at least 50% from renewable energies or waste heat or CHP plants can be sufficient.

That is why I wrote that it always has to be calculated for the specific object!

Rhenish regards

I mean exactly what I wrote: "15% reduction of primary energy demand and at the same time at least 15% better building envelope".

Thank you, then the "correct" (first part of the sentence) was not quite right, I had understood it differently until now. Although I still have not understood what the improvement of the envelope is based on (it is clear to me that the envelope consists of walls, windows, doors, and roof as well as the floor slab or basement walls), I will accept it this way now. In any case, I am wiser than before! Many thanks for the patient answers!

Hello,

as a reminder: the building must undercut the requirements of the applicable energy saving ordinance by at least 15%

I still haven’t understood what the improvement of the building envelope is based on ...

3 examples out of many -

[*]While it is usually sufficient for the building envelope of a KfW 70 efficiency house to install a Poroton T10 - 36.5 - U-value: 0.254, the use of a Poroton T8 - 36.5 with U-value: 0.21 can already be a first building block on the way to the 15% rule.
[*]If the installation of double-glazed windows - along with other measures - is sufficient for the KfW 70 efficiency house status, the installation of triple-glazed windows is another building block.
[*]If 200 mm insulation in the attic usually achieves KfW 70, 240 mm can be the next building block.
[*]etc.

How many building blocks/which measures are necessary is calculated by the energy consultant

Best regards from the Rhineland

3 examples out of many

These are examples how an improvement is achieved. So far so clear. But how does the expert assess the improvement (14%, 15%, or maybe 16%)? One possibility would be the U-value: before 0.254 W/m²K (I added the unit, hopefully correct), after 0.21 W/m²K, difference 0.044 W/m²K or 17% less compared to "before". Of course, this is just the U-value of the stone given in the example. Now one might have to consider a (weighted?) U-value of the entire envelope (meaning: sum of all U*A for all parts of the envelope). Or maybe simply the resulting primary energy demand? Sorry if I am slow to catch on or if I simply cannot formulate my question clearly ...

This is calculated in the energy certificate. The 15% refers to the total of all measures.

The energy performance certificate lists all components with their respective areas and U-values, from which a total U-value of the house is derived. There are also calculated or flat-rate deductions for thermal bridges (a flat-rate deduction usually works better), which are then used to calculate the transmission heat loss (Ht). Therefore, there can also be constructive improvements. Here you have to be 15% better than what the energy saving ordinance requires.

The primary energy demand is a value that takes into account the energy consumption of your heating medium in its production and on its way to you. For each medium, there are predefined calculation factors. The heating demand of the house is then calculated with this factor. For example: heating demand of the house 100 x 1.1 (factor for gas) = primary energy 110. Here again, you must be 15% below the energy saving ordinance.

This is all strongly simplified now, but in my opinion it can only be explained more precisely with an example project. As already mentioned, there are numerous possible measures.