Hydrogeological Report - Geothermal Energy, Air-Water Heat Pump or Ice Storage?

The house was built in 1995. No energy refurbishment has been carried out so far, so almost 30 years have passed without anything really being done from an energy point of view. Is that a problem?

The problem is that the house has a certain energy demand. And that has to be met. Whether by gas, oil, or electricity (heat pump). A heat pump, however, is designed for as low supply temperatures as possible (in new buildings in the depths of winter only 30 degrees). Now your house probably needs 50-55 degrees in winter. Then you could also – to put it bluntly – warm up the heating water with an immersion heater or run several electric fan heaters. That is the big problem with you.

The current energy consumption (gas) is about 25,000 kWh per year. The living area is about 125 m². The house is detached. Temperatures in winter are at a maximum of -10 to -15 °C.

I also see reducing energy consumption as the very first priority. 200 kWh/sqm is very high. With a renovation, you can reduce it by well over half. And that will also have an effect on the heating.

The:

An energy renovation has not yet been carried out, so it is almost 30 years ...

is clearly shown here:

about 25,000 kWh per year. The living area is about 125 m².

For that area, that is quite a lot. There must be a significant draft somewhere, the roof is not or hardly insulated and the windows are worn out. In my opinion, you should first focus on reducing the required heating energy. (First the roof, basement ceiling, then windows and doors) Then recalculate or measure the demand again and only then switch to a heat pump.

: Whether your property is large enough for a ring trench collector or if it qualifies for funding, I unfortunately cannot answer. But I agree with the others here: first renovate energetically so that the heating output can be significantly reduced.

The problem is that the house has a certain energy demand. And that must be met. Whether by gas, oil, or electricity (heat pump).
However, a heat pump is designed for as low supply temperatures as possible (in new buildings in the coldest winter only 30 degrees). But now your house may need 50-55 degrees in winter. Then you might as well - exaggeratedly speaking - heat the heating water with an immersion heater or run several electric fan heaters.

That is the big problem with you.

Alright. I understand. It should be said that the house is currently still rented and we do not know how extensively or sparingly the tenants heat. But the tendency that something needs to be done energetically is definitely there, even if it is heated generously.

We would rather not clad the exterior facade (brick) with an ETICS. Which measures can you recommend?

- Insulation of the basement ceiling?
- Insulation of the upper floor? / attic?

The windows have double glazing (1995) and are actually still okay. Maybe we will check the seals.

Best to hire an energy consultant. For some subsidies, you need one anyway, and first they will make an assessment of which points bring how much savings.