Which heating system? Air heat pump / Gas / Geothermal

We have now been offered 2 options:

City villa with a normal gas system (Kfw 70) and ventilation system with heat recovery
Same city villa with air heat pump for an additional €9000 (Kfw 55 contractually guaranteed) with ventilation system with heat recovery

- Plot with south orientation, no large windows facing north/west and north

Calculations and forecasts were made:
- €2500 savings through Kfw55 loan
- ~€1000 savings from lower interest rates for 10 years
- €1500 savings on gas connection, which is no longer necessary

Effective additional cost €4000

To be honest, I am not particularly interested in the environmental aspect. The electricity needed has to come from somewhere, and electricity energy costs significantly more. Whether and when the €4000 will ever be recouped is also uncertain. And possibly heating with electricity is a really dumb idea. I am not really convinced, on the other hand, the underfloor heating is then prepared for later solar use (or suitable for lower supply temperatures) and also stays up to date with the latest technology for a few more years.
On the other hand, we are slowly reaching what is feasible; the savings are partly not really tangible (e.g. interest) and/or are offset by other costs (e.g. 2 electricity meters or the inspector for Kfw55, who wants €1000 for 1 signature...)

Hello,

In a kfw-55 house, the requirements are very high and the main issue is usually the HT’ (specific transmission heat loss). This depends on the building envelope and building geometry. Building geometry means that the thermal envelope (heat-transferring surface) should be as small as possible and very well insulated. Protrusions, bay windows, and the like should be avoided. The primary energy factor (QP) for a kfw55 house may be at most 55% of the reference building. This value is achieved by using as much renewable energy as possible. In a kfw55 house, it is essential to determine the thermal bridge correction factor (DUWB in W/m²K). With a low heating load and a well-designed heating system, I can imagine that the building can also be heated with a gas boiler. Of course, this must be calculated on a case-by-case basis.

Every heating system has its advantages and disadvantages. A gas boiler converts the energy used (gas) as efficiently as no other heating system.

When calculating the heating load, hot water consumption plays a subordinate role because the heating load is usually greater than the domestic hot water heating load (DHW heating load). If the heating system is a heat pump, a sufficiently large DHW storage tank must be provided.

If you ventilate a lot and like to do so, a ventilation system with heat recovery is recommended. In this, the ventilation system exchanges the air with outside air. Through heat recovery, you can reduce heat losses to a minimum.

If you plan the utility room next to the bedroom, the noise level can be ignored, as the utility room will not be in use while you are sleeping.

Best regards, Erik

Hello everyone,

a different question: have you thought about Zeolith gas heat pumps? And asking around: does anyone here have the device or know someone who knows someone... I would be very interested in any experiences.

Is it really such a big problem with the pellets? Can't you just stack them in front of the house like many generations before you and cover them?

Hello everyone,

a different question: have you thought about zeolite gas heat pumps? And asking around: does anyone here have the device or know someone who knows someone... I would be very interested in any experience.

Me too.

Sylvia