ᐅ Is a brine-to-water heat pump still worthwhile for a KfW 40+ energy standard building?

Hello everyone,

We are planning a prefabricated house built to KfW 40+ standard, including two residential units of 95 m² (1,023 sq ft) each. One of these units will be rented out. Unfortunately, four different suppliers have given us four different opinions regarding the heating system. Some say that a ground-source heat pump (brine-to-water) is not worthwhile because of the drilling and costs, especially since we also have ventilation systems with heat recovery, so an air-to-water heat pump would be completely sufficient. Whether to choose a monoblock or split system is also debated among the suppliers. As a layperson, it’s quite confusing.

What is your opinion on this?

Best regards

009_frank schrieb:

Some say that a ground-source heat pump is not worth it (because of the drilling and the costs) since we also have ventilation systems with heat recovery, and therefore an air-source heat pump is completely sufficient.

If I were a complete beginner, I would conclude from this: The ground-source heat pump is more expensive but also better, while the air-source heat pump is just "enough" (grade: sufficient).

What do you want?

How much do you save annually on heating costs approximately with the ground-source heat pump? Then you can calculate when it will pay off.
However, as a landlord, you won’t get any additional rent for the ground-source heat pump in the rented part.

My personal opinion: Ground-source heat pumps are no longer worth it from KfW40 standard onwards. The additional cost will never be recovered through lower heating expenses.
Example for a 150m² (1,615 sq ft) house: heating costs with an air-source heat pump are €600, with a ground-source heat pump 20% better = €480.
The price difference between an air-source and a ground-source heat pump is about €6,000, resulting in a payback period of 50 years.
It’s easy to calculate this roughly.

For rental properties, an air-source heat pump is preferable anyway, see post by [USER=9254]@haydee

P.S. It’s not much different with KfW 55 standards either. Only a ground-source heat pump with a horizontal trench collector or similar system is a sensible alternative, as it eliminates the need for drilling. With drilling, see above.

6000 euros for a borehole would be affordable but it also depends on the region.

In the Rhine Plain, I would only use an air-to-water heat pump.

In the deep Black Forest at 800m (2600 feet) and above, I might consider it. If I were building 300m2 (3200 square feet) or more, I would consider a ground-source heat pump with an additional fireplace.

Better to have pipe spacing in the bathroom at 7cm (3 inches) and a proper heating load calculation.