Which heating system is currently the best?

It was a question purely out of interest without any concrete reference.
Regards

I have to "go back" a bit here – unfortunately, I wasn't around for a few weeks.

Air heat pumps are not uncritical in large parts of Germany (south, east, mountainous regions, etc.). Even if it can "work well" in a KfW40 house, the risk of too high operating costs is still high ... especially since it depends not only on the device but also on good planning and installation ... which is much harder to get than you might think.

If that doesn’t fit well, the difference to a gas heating system (at today’s still valid gas prices) can quickly become quite small.

What’s so bad about a heating system paying off compared to others only after 10 years?
Usually, you live in your own home for at least 5 x 10 years or even longer.
And a heating system is expected to last 15-20 years ... so if after 10 years it is already advantageous overall compared to others, it has paid off.
The question is also how strong the advantages are in the following years ... once the additional investment has been saved.

> "In an uninsulated old building, on the other hand, a heating system with high fixed costs and low consumption (e.g., geothermal heat pump) would be the better alternative."

Definitely not!
That is thinking too simply. There are many other factors involved here ... for example, that a heat pump generally has a significantly worse efficiency at the high flow temperatures usually required in old buildings. Heat pumps react quite differently to ambient conditions than gas, oil, pellets, etc.
(If you had taken a pellet heating system instead of geothermal as an example here, it would look different.)
See also the article from €uro dated 29.9.12.

What is exactly suitable results from the heating load and heat demand calculation.
And of course also from the individual consumer behavior.

You can also "calculate" the heating load yourself, at least as accurately as necessary for selecting the heating type. (No, I will not post a link now. Just google roughly "how to calculate heating load," you will find something.)

The "predominant solar thermal heat supply of the house" is certainly a great thing.
But it is the most expensive option, since you 1. need a very large solar thermal system (in the order of 50 sqm solar thermal + at least 5,000 L special storage) and 2. a second heat generator for the "sun-poor" weeks and months.

Photovoltaics only make you independent if you also install a storage (battery) ... which alone costs at least €10,000 in a reasonable size.

Basically – if the house fits – I would recommend geothermal + controlled residential ventilation/heat recovery.
For a house at KfW55 or better. Depends on the investment amount possible today ... and how you estimate future energy costs.

Leave out solar thermal in this case.
Not because the efficiency is poor, but because geothermal delivers heat so cheaply that the additional investment can no longer be saved.

Also basically: As much as necessary – but as little as possible.

So nothing with exclusive fancy stuff in the heating system, but for example a compact brine heat pump (heat pump, pumps, hot water preparation/storage, control ... all in a cabinet-like unit about 60x70x200 cm) and a well/individually dimensioned underfloor heating. Best a concept that works without room thermostats, so it "regulates itself."

Heating with wood or pellets is slowly becoming too expensive.
Unless you have your own wood and want + can do it.

I don’t like the idea of solar thermal + heat pump or log wood boiler.
I have already mentioned why ... roughly speaking.

And above all, don’t believe anything that doesn’t somehow make sense to you ... like e.g. achieving up to 23°C room temperature with 26°C flow temperature in wall heating ... that might work where it doesn’t get colder than +10°C (southern Italy, Africa ... where the Energiefuxx probably is) ... but not in large parts of Germany.

Wall heating in new buildings also has a mostly overlooked problem today:

Large areas are now mostly windows ... you want light and sun.
That leaves not many walls for the wall heating ... and even if there are enough, one should know that these "radiant walls" must not simply be "shaded" by cupboards, large pictures, etc. ... otherwise the principle no longer works. By the way, with wall heating you also have to do without warm floors.

So, that’s it for now.

Regards
-Martin-

....Air source heat pumps are not unproblematic in large parts of Germany (south, east, low mountain regions, etc.).

I am not aware of any system that is generally or unconditionally "unproblematic"!

...especially since it depends not only on the device but also on good planning and installation ...which is much harder to get than one might think.

An exact sizing and planning is required for every system, even for an allegedly trivial gas condensing boiler with radiators. Even in the latter, significant errors are made.

The upper curve in each case is what I have found in real installations. By the way, good planning/sizing is very easy and inexpensive to obtain.

...You can also "calculate" the heating load yourself, at least as accurately as is necessary for choosing the heating type. .....Just google approximately "how to calculate heating load," you will definitely find something.)...

Hardly, once estimated => remaining guessing game!
Without room heating loads, a comprehensive assessment is hardly possible or sensible. The standard heating load is virtually produced as a "by-product." Therefore, any "pre-estimation" can be omitted.

...Photovoltaics only make you independent, ....

It is not absolutely necessary to be independent; it is completely sufficient if a photovoltaic system delivers as many kWh in the annual balance as are required for heating, hot water, ventilation, and possibly household needs.

...Also fundamentally: As much as necessary - but as little as possible.

Correct!

...Wall heating in new buildings also has a usually overlooked problem today:...

Energetically worse at exterior walls than underfloor heating, unless improved insulation is present. On the other hand, significantly less inert!

...that these "radiant walls" must not simply be "shaded" by cabinets, large pictures, etc.... otherwise the principle no longer works.

The same applies to underfloor heating => inactive or non-active heating surfaces. This must be taken into account in the design. Additionally, the choice of floor covering plays a significant role. Thick "Persian" rugs or parquet can partly reduce energy efficiency significantly.
Comparable to a towel radiator in the bathroom that has been covered accordingly. If this is considered in the balance, achieving room temperature is likely difficult. Then usually only increasing supply temperature and/or mass flow helps. A weekend, especially a heat pump, is not at all pleased with this.

...By the way, you also have to forgo a warm floor with wall heating (.

With the suitable operating temperatures in heat pumps as heat generators, "warm feet" are hardly still a criterion.

Best regards

In general, I would always include solar. However, differentiation is also necessary. The most efficient and simplest system is the Drain-Back solar system with pressureless storage tanks, combined with wall heating. The design of the wall heating covers about 50% of the floor area. After all, not 100% of the walls are blocked by furniture. The Drain-Back system should be supported by a heat pump or pellet boiler. A large storage tank is mandatory so that all the heat can also be stored.

The problem is usually that the heating engineer or planner does not know the systems and is resistant to learning. This is not meant to sound derogatory, but it is also a societal problem and the same applies to other consumer goods. The customer is not allowed and should not think, but rather follow the words of the (consumer) industry and its advertising, which violates all norms, regulations, technical formulas that are not to be understood (mostly not even by the salespeople) and uses these as a pretext, because they were developed only for that purpose.

The question should be: How must a solar system be designed for the customer and why must it be executed as a pressurized system?

1. durable, long-term and reliable function

This can only be achieved if:

a) no overheating – or the collectors do not go into stagnation, as most damage arises from this.
b) frost-free – same situation as above
c) lime-free – because this reduces performance by up to 50%
d) guaranteed rust-free – because on average the storage tanks have to be replaced every 10 years
or are so corroded inside that an adequate performance is no longer possible.

2. avoid superfluous and repair-prone components.
A solar system is not a heating system and does not necessarily have to be built like a pressurized system. In self-draining Drain-Back systems with pressureless storage tanks, materials can be omitted that initially cost money in purchase and usually have to be replaced in case of overheating and frost, as well as after some years. The following components are not required in Drain-Back systems with pressureless storage tanks:
- expansion vessels
- flow regulators
- safety valves
- automatic air vents
- glycol heat transfer fluids (proper Drain-Back systems are operated with normal water)
- filling fittings
- sacrificial anodes

These devices usually add installation costs of 700-1000 €, thereby directly bringing the customer trouble, as these parts must be replaced at intervals of at least 5 to 10 years.
Going a step further, separation stations are needed in the combination of steel storage tanks and underfloor heating, which in turn cost 1000-2000 €. These separation stations must be installed because underfloor heating made of polypropylene is not oxygen-tight and transports oxygen without a separation station into the steel storage tank, which would immediately cause corrosion and sludge formation in the storage tank. If pressureless polypropylene storage tanks are used, they are made of the same material as the underfloor heating, and the underfloor heating can be operated directly with the storage water without a separation station. So no rust and no sludge in both underfloor heating and storage tank, usually for 40 years. Since most heating engineers have grown up with steel storage tanks and there are only very few suppliers who manufacture these robust, temperature-resistant, statically stable layered storage tanks (without repair-prone inner liners), it will take some time before this is established in the minds of the "experts". End customers, exhausted after numerous consultations and trade fair visits, have understood this and focus on a rational design with a Drain-Back system and pressureless storage tank, which really saves the customer money, energy, maintenance, and trouble.
Combined with efficient surface heating, the customer is then where they are more than satisfied.
That it also works on a "large" scale is proven by a system with a 130,000 liter layered storage tank and 200 VRKs in Germany.