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

taskyyy schrieb:
Unfortunately, the current owner cannot provide exact information about the heating load. I can only estimate it based on the available data.

She still has the old radiator heating system. In January and February, the heating was set to level 3, and it was already quite warm. The heating system is a Bruderus Logana G 105 from 1988, energy rating D.

So, to summarize, it’s best to consult an energy advisor, insulate the facade and roof, install triple-glazed windows, add underfloor heating upstairs and downstairs, and then a heat pump definitely makes sense, right?

Are you installing the flooring yourself? If so, I would go for underfloor heating. If not, it’s quite a lot of work. As you describe it, that’s the absolute ideal situation.

CC35BS38 schrieb:

As long as it’s just the healthy skepticism of laypeople without expertise, that’s fine. There are whole institutes dedicated to this, so they must know what they’re doing.

There are many institutes whose main job is to deal with these issues, and yet they failed to foresee the crisis. Mortgage-backed securities and the financial crisis they triggered were an illusion of knowledge and control. Even as late as mid-February 2020, no expert seriously predicted what COVID-19 would mean. The supply chain disruptions caused by it were also completely off their radar. Central banks—which are supposed to be inflation experts—are now realizing that inflation is not as temporary as they claimed for nearly two years. And obviously, just a month ago, no one anticipated that the war in Ukraine would lead to shortages of nails, tiles, and roof shingles.
The vast majority of “experts” were completely clueless in all these cases. I’m sorry, but when it comes to the future, experts are just knowledgeable people who don’t really know what’s ahead. A look back at past predictions confirms this far too often. On top of that, many experts tend to go with the prevailing winds. The statements from the Leopoldina over the last two years are a perfect example. Neither independent expertise nor critical thinking was evident there.
And yes, @Deliverer is right, it’s important to get started. But it’s equally important to choose appropriate solutions rather than simply applying one-size-fits-all solutions like Procrustes. Only solutions that are moderate, sensible, targeted, and therefore economically viable will gain lasting acceptance. At least, that’s my liberal hope for society 😉
Well, that’s all I wanted to say on this topic. I’d rather not hijack the thread any further.

Deliverer schrieb:

It even makes sense with less extensive measures—as you describe, that would be perfect. (Maybe add photovoltaic panels on the roof since it will be replaced anyway.)

Yes, photovoltaics are planned, but the roof faces east, though with a 40-degree (40°) pitch.

CC35BS38 schrieb:

Are you installing the flooring yourself? Then I would go for underfloor heating. If not, it’s quite a lot of work. What you describe is the ideal situation.

Yes, there is carpet installed now, so it will naturally be replaced. Floating screed will be used. Then underfloor heating upstairs and downstairs.

However, if I want to get funding for new windows, they have to be triple-glazed. And if I install those, I would also have to insulate the facade. Or is it more worthwhile to install a heat pump with the existing facade and then only double-glazed windows?

Triple-glazed windows are not a problem, even with non-insulated facades. In 99% of cases, mold is caused by ventilation and heating issues.
If you are installing underfloor heating anyway, then consistently eliminate thermal bridges. Increase the insulation on the upper floor ceiling to 20cm (8 inches).
Then the heat pump will work fine.

You don’t necessarily have to renovate the facade and windows at the same time, right? What is the condition of the facade and windows? How old are they? And are they insulated at all?

CC35BS38 schrieb:

You don’t necessarily have to renovate the facade and windows at the same time, right? What is the condition of the facade and windows? Age? And are they insulated at all?

The facade actually still looks good, no cracks, all white. The roof overhang is about 1m (3.3 feet).
The building was constructed in 1973 but has been well maintained.

The U-value of the facade is 0.97 W/m²K (0.17 BTU/(ft²·°F)). It consists of:
Calcium silicate brick (115 mm (4.5 inches))
Polystyrene insulation (20 mm (0.8 inches))
Calcium silicate brick (175 mm (6.9 inches))

Additionally, there is partial slate cladding. However, it should be noted that there are very large window areas: the entire south-facing side is almost entirely windows, both top and bottom.

The windows are wooden with insulated glazing, so they probably should be replaced.

The top floor ceiling still has 10 cm (4 inches) of mineral wool insulation. The ceilings elsewhere are made of reinforced concrete.