Type of heating for a 400 sqm multi-family house with KfW 55

Since our previously planned heating system (brine heat pump) literally fell through (requirements from the environmental authority for the groundwater protection area IIIa), we are looking for alternatives but are still not clear about the ideas.

Here are a few frame data:

- The new building will have about 390sqm (14x14m, two apartments per full floor, two smaller apartments on the staggered floor).
- We have to build KfW55 (requirement from the city).
- Heating load estimated about 16,000W/a
- Controlled residential ventilation planned


We therefore see three alternatives:

- Gas & solar thermal: It will be very tricky to get this approved as a KfW55 house. Needs to be calculated more precisely. Otherwise, it seems very attractive to us.

- Air-water heat pump: The warm area at the Rhine speaks in favor of this, which promises only little electric supplementary heating in winter. Against it, for us, is the bulky unit in the (front) garden, especially with the above-mentioned amount of energy. Does anyone of you have experience with air-water heat pumps for this scale, possibly also for indoor installation?

- Well heat pump: Would be possible despite the groundwater protection area, but an expert wants 750€ for the test drilling to be able to make informed statements.

- Trench collector is out, as the plot is too small for it.


What would you advise us?

Pellets are also possible, but require storage.

Water-water heat pumps are super efficient if possible and approvable.

Google "Ringgrabenkollektor". It is a more economical (in terms of space and financially) installation alternative to the surface collector.

Pellets are also possible, but they require storage.

Water-water heat pump is super efficient if possible and approvable.

Pellets are exactly out for the reason you mentioned. Especially since prices are rather increasing here and we are building in an urban area.

Water-water just unfortunately wants 750€ upfront to find out if it would even work. Do you have any further experiences/ cost points here compared to the air-water heat pump?

Google "Ringgrabenkollektor." It is a more economical (in terms of area and financially) laying alternative to the surface collector.

I had already done that and with this tool I only came to 7-8KW/a for our property, since we will have already built on almost 200sqm of the 600sqm plot.

There are also geothermal baskets. For example, a Maxi-basket with 1.6-2.0 kW each. Requires 50m² in parallel arrangement. In theory, for 400m² that would be 8 baskets with a minimum of 12.8 kW.

There are also gas heat pumps. For example, with zeolite adsorption.