ᐅ Hybrid heating system: Is combining a heat pump with a gas condensing boiler a practical solution for renovating older homes?

The heating load (calculated room by room) should be determined by a qualified energy consultant or, even better, an engineering firm. It will definitely not exceed 10 kW.
After that, you no longer need gas. You might not even be able to get gas contracts anymore, and possibly not receive gas next winter even with a contract.

Install a 10 kW monoblock heat pump, and that will be sufficient. Or even better, insulate first and then use a smaller heat pump.
If retrofitting underfloor heating is an option, I would recommend equipping all rooms with it if possible. This eliminates the need for a heating buffer tank and mixing valves, and it significantly lowers the supply temperature. If underfloor heating is not feasible everywhere, wall or ceiling heating is also possible. The main goal is to activate large surface areas.

Then install as much photovoltaic capacity as the roof area allows, and you are prepared for the future.

Deliverer schrieb:

The (room-by-room) heating load should be determined by a qualified energy consultant, or even better, an engineering firm. It will definitely not exceed 10 kW.
And then you stop using gas altogether. You probably won’t even get gas contracts anymore, and next winter, possibly no gas even with a contract.

Install a 10 kW monoblock heat pump, and that’s it. Or even better, insulate first and then use a smaller heat pump.
If retrofitting underfloor heating is an option, I would equip everything with it if possible. This eliminates the need for a heating buffer tank and mixing valves, and really lowers the supply temperature. If it’s not possible everywhere, wall or ceiling heating is also possible. The main thing is to activate large surface areas.

Then add as much photovoltaic as the roof space allows, and you’ll be ready for the future.

Okay, thanks. Yes, I just thought because the house is older, built in 1972, and the living area is 142 m² (1,527 ft²).
But I suspect the heating contractor wants to push gas because it will bring more long-term maintenance work for them.

However, I do have to consider the insulation measures already done by the previous owner, for example the 10 cm (4 inches) of wool insulation in the top floor ceiling.
The windows currently have double glazing, but they will be replaced with double-glazed units or possibly triple glazing if the façade is insulated after all.
I’ve just always heard that heat pumps only pay off in new builds or when the whole house is extremely well insulated—according to the latest standards and so on.

taskyyy schrieb:

I’ve just heard everywhere that heat pumps only make sense in new buildings or if the insulation is extremely thorough everywhere—according to the latest standards, etc.

That is definitely not true. Right here, next to me, you’ll find plenty of people who prove the opposite.
And regardless of whether it “makes sense” financially, virtually all houses will have to be converted to heat pumps within the next 20 years. Unfortunately, there won’t be other options to achieve the necessary CO2 neutrality by then. From an ecological perspective, it would be disastrous to install anything else now. Economically, it is very likely the same.

Deliverer schrieb:

From an ecological point of view, it would be disastrous to install anything else now. Probably economically as well.

I disagree with you on both points. With a high heating load and high supply temperature, the efficiency of a heat pump is simply poor. As a result, a lot of very expensive electricity is wasted, which even in 10-15 years will mainly come from coal and gas during winter. So it is neither ecological nor economical.

Although politicians are currently saying otherwise, they will come to grips with reality the hard way. Starting with the shortage of installers for heat pumps, tradespeople for the necessary major renovations, missing power lines, and so on.

WilderSueden schrieb:

... electricity that will still mainly come from coal and gas in winter even in 10-15 years. So neither ecological nor economical.

People with much more expertise than all of us combined see it very differently.
@TE I initially accepted the heating load as given, my mistake. Where does it come from? It seems very high considering that everything except the facade matches and the house is of average size. This is crucial for making a decision.

CC35BS38 schrieb:

People with much more knowledge than all of us combined see it very differently.

Predictions are difficult, especially when they concern the future 😉
So I simply approach the issue, following Taleb and Occam, with as few assumptions as possible. In winter, the sun shines little and stays low, so photovoltaic systems are out of the question. On top of that, here in the south we often have fog, and sometimes no sunlight is seen for up to two weeks in winter. There is sometimes wind, but often as storms and not very reliable. So the electricity would have to come from the windy north, but the power lines there face opposition from citizen groups in almost every second village. Wind turbines also face resistance. What else is left?
We are currently phasing out nuclear power; hydropower is considered "renewable," but nowadays you won’t get a permit / planning permission to flood an alpine valley in an environmentally friendly way. German geography doesn’t offer much anyway, even if one wanted to.
Basically, you also face the problem that unreliable energy generation like solar and wind must be massively oversized (expensive and not exactly ecological) to cover unfavorable conditions. Even with grid-scale storage (also expensive).

In the end, only coal, gas, and buying electricity from neighbors remain. Everything else relies on miracle technologies. Expert opinions are all well and good, but healthy skepticism is also important.