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

Good evening everyone,

We want to replace our gas heating system, which is over 30 years old, with a new one. Additionally, we plan to remove the traditional radiators and install underfloor heating throughout the entire house. We were thinking of milling the pipes into the existing screed, unless a complete renovation with new screed, etc., would be more sensible?

1) Hydrogeological Expert Report: We had considered a geothermal heat pump (ground source heat pump) as the heating option. However, since the building is located in a water protection area, a hydrogeological expert report is required to assess whether geothermal energy is permitted and to what extent (depth, brine, number of boreholes). The water authority is very strict about this. I have attached the information sheet with the requirements for the report.

Have you ever heard of such a hydrogeological expert report, and do you know what the costs might be? We really have no idea how to estimate this and wanted to ask if anyone has had similar experiences.

2) Comparison of Air-to-Water Heat Pump and Geothermal Systems: These two systems are often compared. One person says one thing, another says something else. But I haven’t found or heard any clear facts yet. Geothermal is said to be more efficient, but air-to-water heat pumps have become very powerful and therefore potentially more cost-effective. The trend seems to be towards air-to-water heat pumps, which are somewhat cheaper to install than geothermal systems. Prices have increased significantly everywhere recently. Could someone provide us with more detailed information on this topic to help with our decision?

3) Ice Storage Heating: The heating/well installer even suggested an ice storage heating system as an alternative because it does not require a permit. However, I don’t know anyone who uses such a heating system. What do you think about this?

Thank you very much for your help and best regards!

FCBenne04 schrieb:

We want to replace our gas heating system (over 30 years old) with a new one. In addition, we plan to remove the traditional radiators and install underfloor heating throughout the entire house.

What about: external wall insulation, insulation of the basement ceiling / roof / upper floor ceiling, new windows, etc.?
Installing only underfloor heating plus a heat pump does not automatically mean low heating costs.
What does the room-by-room heating load calculation say?

FCBenne04 schrieb:

Unless a complete renovation with new screed, etc., makes more sense?

I always see that as more practical since you can be more flexible with installation (different (larger) pipe sizes and spacing – a heat pump needs flow, flow, and more flow) and it doesn’t really cost much more. Keep in mind that not only the heating system itself but also the related construction work is often subsidized.

FCBenne04 schrieb:

2) Comparison between air-to-water heat pumps and geothermal heat pumps: These two systems are always compared with each other. One person says this, another says that. But I haven’t really heard or found solid facts about it yet. Geothermal is supposed to be more efficient, but air-to-water heat pumps have become very powerful as well and therefore might be more cost-effective. The trend is rather towards air-to-water heat pumps, which are somewhat cheaper to purchase than geothermal systems. Prices have increased sharply everywhere recently. Can someone provide us with more information on this topic to help with our decision?

Both systems actually work very well. Just keep in mind that the additional investment for geothermal will likely never pay off over the system’s lifetime (thanks to the drilling, it can easily be thousands of euros more expensive than a “simple” air-to-water heat pump. Far from “somewhat cheaper.”). The higher efficiency means roughly €47 in heating costs instead of €50 per month with the air-to-water heat pump in a new build.

FCBenne04 schrieb:

The heating/well installer even suggested an ice storage heat pump as an alternative,

Unusual, but apparently it works. In over 20 years in the construction (and financing) industry, I have never seen it in real life. Combining geothermal and ice storage is by far the most expensive option (the ice storage alone likely costs five figures – in addition). As far as I know, it’s suitable for buildings with very high heating and cooling demands – so commercial properties.

Axolotl2022 schrieb:

The increased efficiency means heating costs of €47 instead of €50 per month with the air-to-water heat pump for a new building.

Could this potentially be relevant for an older house with a large living area? Just asking.

Unfortunately, I don’t have much to add, except that my parents are currently facing similar questions. (Water protection area but not the highest protection level—I would need to check exactly what that means. An old, large house where several insulation measures have already been carried out. Soon the oil heating system will need to be replaced, and nobody really knows what it should be switched to...)

mayglow schrieb:

Could this become relevant for an older house with a large living area? Just asking.

Yes, of course. The poorer the condition of the house, the more likely you are to recoup the additional cost of geothermal heating. Therefore, the current energy consumption as well as the expected consumption after renovation are important. It would also be relevant to consider the location of the house and the typical winter temperatures to be expected.

mayglow schrieb:

Could this possibly become relevant for an older house with a large living area? Just asking.

Yes, it can. In that case, the difference becomes smaller.

BUT: The additional effort for the old building can be better invested in other energy efficiency measures. Because then the house will probably consume less energy than with the efficient ground-source heat pump.

We are also building in a water protection area and planning to use a brine heat pump. Deep drilling is not allowed, but horizontal ground collectors are permitted. I spoke with the local water authority, and it was basically no problem... there are a few requirements regarding the installation depth (x meters above the groundwater level), pressure monitoring of the brine circuit to detect leaks (easy), and the brine itself (easy). Connection must be done by a certified professional, that’s about it as far as I remember.

We are planning a trench collector system.
A hydrogeological report usually refers to the groundwater level, but we don’t need one because the collector will only be installed at a maximum depth of 2m (6.5 feet) and our groundwater is much deeper.