ᐅ Heating system for a 400 sqm multi-family house with KfW 55 energy standard

Since our originally planned heating system (ground-source heat pump) literally fell through due to environmental authority regulations for the groundwater protection zone IIIa, we are now looking for alternatives but are still uncertain about the options.

Here are some basic details:

- The new building will be around 390sqm (14x14m, two apartments per full floor, two smaller apartments on the top recessed floor).
- We must build to KfW55 standard (requirement from the city).
- Estimated heating load about 16,000W/year
- Planned controlled residential ventilation system

We therefore see three alternatives:

- Gas & solar thermal: This will be very challenging to achieve within a KfW55 standard building and would need a more detailed calculation. Otherwise, it seems very attractive to us.

- Air-to-water heat pump: The mild climate in the Rhine area speaks in favor, as only little electric supplementary heating should be needed in winter. Against it is the large unit in the (front) garden, especially with the above-mentioned heat demand. Does anyone have experience with air-to-water heat pumps at this scale, possibly also with indoor installation?

- Well heat pump: This would be possible despite the groundwater protection zone, but an expert wants €750 for a test drilling to provide a reliable assessment.

- Trench collector is not an option since the plot is too small for it.

What would you recommend?

Pellets are also an option but require a storage area.

A water-to-water heat pump is highly efficient if feasible and approved (building permit / planning permission).

Google “ring trench collector.” It is a more economical installation alternative to the horizontal collector in terms of both area and cost.

Alex85 schrieb:
Pellets are possible too, but you need storage space.

A water-to-water heat pump is very efficient if feasible and allowed by building regulations / planning permission.

Pellets are ruled out exactly for that reason you mentioned. Besides, prices here tend to rise, and we are building in an urban area.

Unfortunately, a water-to-water system requires an upfront cost of about €750 to determine if it’s even possible. Do you have any further experience or cost comparisons with air-to-water heat pumps?

Zaba12 schrieb:
Search for Ring trench collector. It’s a more economical installation alternative—in terms of area and cost—compared to a ground loop collector.

I already looked into it, and using that tool I also calculated around 7–8 kWh/year for our property, since we have already built nearly 200 square meters (2,150 square feet) on our 600 square meter (6,460 square feet) lot.

There are also geothermal baskets. For example, a maxi basket with 1.6-2.0 kW each. When arranged in parallel, it requires 50m² (540 ft²). Theoretically, for 400m² (4,300 ft²), you would need 8 baskets with a minimum of 12.8 kW.

There are also gas heat pumps available, for example, using zeolite adsorption.