ᐅ KfW 40 standard, ground-source heat pump worthwhile or better air-to-water?

wiltshire schrieb:

Take a look at the funding options available for ground-source heat pumps. I’m not fully up to date, but different subsidies have significantly narrowed the cost gap in the past. The efficiency of a ground-source heat pump is independent of the weather. The annual performance factor remains consistent. I doubt that only €50 savings would result. If you build a 150 sqm (1615 sq ft) house to KfW55 standard, you have a calculated energy demand of 55 x 150 = 8,250 kWh per year. The ground-source heat pump achieves an annual performance factor of 4, and the air-to-water heat pump averages 2.8 (assuming the maximum declared figure is not maintained throughout the year). This means the ground-source heat pump consumes 8,250 / 4 = 2,062.5 kWh, and the air-to-water heat pump consumes 8,250 / 2.8 = 2,946.43 kWh, a difference of about 900 kWh. At €0.30 per kWh, that amounts to €270 per year.

From my point of view, another advantage of the ground-source heat pump is its cooling capability and notably quieter operation.

My preference – without having analyzed the actual expenses (cost minus subsidies) in detail – would be the ground-source heat pump.

Thank you very much for your assessment. I have also looked into funding options but have found nothing significant for NRW, so assuming additional costs of €12,000 (drilling, etc.), the payback period would be 44 years. I keep coming back to the thought that the house has such a good energy rating and we don’t experience winter temperatures below -10°C (14°F) here.

itizniti schrieb:

I keep coming back to the thought that the house has too good an energy rating and we don’t get -10 degrees in winter here anyway.

One thing is the payback period, another is what makes you comfortable.
I know a few homeowners who chose drilling instead of an air-to-air heat pump because they were concerned about problems with the outdoor unit. It’s certainly not common, but it does happen occasionally, as you can also read here from time to time.
Our Daikin air conditioning system, which I sometimes use for short-term heating upstairs, hums very softly and I don’t hear it indoors. Outside, there are no neighbors nearby, and even if there were, it wouldn’t be audible. It’s different at a house further up the street where I can actually hear the outdoor unit clearly when passing by. That kind of buzzing would be a nightmare for me, which is why I didn’t go that route—even if more than 90% of such concerns are unfounded; still, it can be an additional factor in your decision.
The “energy rating,” or what you probably mean by that, only partly depends on the heating method chosen. As the occupant of a very well-insulated house, I would advise aiming for a “good energy rating,” because then the heating demand is lower; the house loses much less heat than a less insulated one, and this already makes a noticeable difference at 10°C (50°F) and above, regardless of how harsh winters are in Duisburg.
At first, I had a strong wind noise here that has mostly been solved now, but it was bad enough that I considered selling the house. The neighbor with the buzzing heat pump was here recently and it doesn’t bother him at all—the lucky guy.

Honestly, if I were you, I would worry less about the type of walls unless you have specific or necessary reasons for choosing a particular building material. Instead, I would focus much more on the many small details in the house that will truly affect your daily life: the floor plan, window layout, type of heating system (underfloor heating, wall heating, wood stove, etc.), flooring, lighting, and so on. All these aspects can make your home cozy and beautiful regardless of which type of masonry you use.
Fundamentally, I would also choose the heating system not only based on payback but from a personal comfort perspective, whatever that means to me.

Many thanks, Auraki!

I think I may have been unclear in some parts when I said “good energy value.” What I actually mean is the high energy efficiency rating or the low final energy consumption of the house. Because of the good efficiency class, my energy consumption is so low that the costs are no longer proportional to the savings. If money were no object, I would choose a ground-source heat pump. However, I’d rather invest that money in the garage or the new kitchen.

Regarding the choice of masonry, I don’t fully agree with you because I want to make sure I won’t have to replace the external thermal insulation composite system (ETICS) panels in 30 years. But of course you’re right that other factors will have a much greater impact on my daily life. I’m already working on those issues, and both general contractors (GCs) are flexible with the floor plans, so that won’t be a problem.

itizniti schrieb:

I don’t fully agree with you on the choice of masonry, since I want to avoid having to replace the ETICS panels in 30 years as much as possible.

There are certainly different deal-breakers for many decisions, but if you want to avoid ETICS, whether everyone understands that or not, then that’s already clear. You can also build with thicker walls or use a different type of insulation. For example, we have 14cm (5.5 inches) of wood fiber insulation under the wooden cladding, but I could also have just built with a 50cm (20 inches) thick wall; in our case, this came up during construction due to somewhat unusual reasons with the general contractor.

Do you want to build a highly insulated house (with or without subsidies) or only meet the legally required standard? As I said, I would decide this myself based on my own parameters and background.

itizniti schrieb:

I keep coming back to the idea that the house has a very good energy rating and we don’t experience temperatures as low as -10°C (14°F) in winter here.

Well, then the decision is almost made.
When choosing, I would place the highest priority on noise levels, not just outside but also indoors.

itizniti schrieb:

I’m wondering if a ground-source heat pump really pays off. The drilling costs are around 12,000 - 13,000 euros. Basically, I’m questioning whether I would ever recover that money by installing such a ground-source heat pump.

Instead of deep drilling, you could also consider a radial collector (horizontal ground loop). If the property is suitable and you plan to do some of the work yourself, it might also be financially worthwhile to go for a ground-source heat pump.

I don’t have personal experience with this, but in other house technology forums, there are many interesting posts and reports with instructions on how to proceed.