ᐅ Cabinet with air-to-water heat pump and water storage tank. Does anyone know this system?

Lucrezia schrieb:

Why do ventilation and heating need to be separate?

Technically, there is no reason to combine a mechanical ventilation system with heat recovery and a hydronic heat pump: the mechanical ventilation already uses the house’s waste heat, which would not be sufficient for the heat pump anyway.

In case of replacement or maintenance, you are tied to one very expensive, specialized device from one or only a few manufacturers. Why would you want to do that?

A mechanical ventilation system with heat recovery can be replaced for around 3,000€ (approximately $3,200). Hydronic air-to-water heat pumps as monoblock units also start at about 3,000€ (approximately $3,200), with the hot water storage tank installed separately. Split heat pumps with integrated domestic hot water tanks are naturally more expensive. It is rare for everything to break down at the same time. Technology continues to evolve, and when replacement is needed, you want to have free choice on the open market.

Apparently, unsuitable combined units are sometimes installed by some general contractors; the worst cases are pure air heaters. Homeowners often return to forums after a few years, confused by very high electricity bills since these systems basically heat directly with electricity despite the expensive heating equipment.

For me, combined units are initially a sign that things will go wrong. With proper planning, you should be able to achieve an operating energy consumption close to that of a good separate heat pump.

fragg schrieb:

But call him and ask for the manufacturer and model designation, then we can take it from there.

And also the building’s thermal transmission loss as well as the heating load.

Lucrezia schrieb:

Regarding ventilation, we are open; as far as I’m concerned, it could also be without it, I have no problem with airing the rooms..

Then just leave it out. Central controlled mechanical ventilation systems cost from around 10,000 euros and are purely a comfort feature.

Could it be the Stiebel Eltron LWZ 604 Air or the Tecalor TCO 2.5?

Combination units for domestic hot water, controlled residential ventilation, and heating with an inverter air-to-water heat pump.

It’s a hybrid system. On one side, there is an air-to-water heat pump with a refrigerant circuit and compressor, similar to the LWZ 504. This eliminates the disadvantages of a purely air-based heat pump. On the other side, instead of underfloor heating, the ventilation system is connected.

As far as I know, it has been on the market since autumn 2018. In 2017, it was intended for passive houses. I heard in winter that it is also installed in somewhat less well-insulated homes.

Lucrezia schrieb:

The warm air is 'distributed' by the ventilation system, the entire unit costs about 20,000 € and requires very little maintenance.

To me, that sounds ideal. We could install our preferred wooden flooring without underfloor heating, save a lot of money, and expect less maintenance.

You really can't build anything much worse for heating, except for supply temperature. You basically have a proper passive house.
Why do you think you save a lot of money with 20,000 €? Why did you want to do without underfloor heating?
Underfloor heating is usually the best solution, and you’re not tied to any single heat source.

Thank you very much for your answers!!

@haydee you’re awesome, that’s exactly the device the consultant mentioned.

I don’t know much about heating and technology, which is why I asked this question.
So the conclusion is that water, as usual, is best suited as a heat storage medium.
Only if it’s a real passive house with minimal and very localized heating needs, could this hybrid system be worthwhile: it heats up quickly but would lose heat quickly as well.
Is that correct?

Underfloor heating
I love thick wooden floors. Of course, they can be combined with underfloor heating, but the heat conduction is poor.

As an alternative, I only know wall heating (with clay it would be perfect), but that is considerably more expensive than underfloor heating. That’s why I thought this “cabinet concept” might be interesting.

Lucrezia schrieb:

Only if it is a true passive house with minimal and very limited heating demand could this hybrid system be worthwhile: it heats up quickly but would lose heat just as fast.
Is that correct?

Basically correct. However, a heat pump cannot heat up quickly. Ideally, it runs continuously at a low or appropriate output and is not oversized.

The problem with air heating is that air transfers less heat compared to water. To warm a normally insulated house, the air temperature would have to be raised so much that the heat pump’s efficiency drops significantly. The issue with purely exhaust-air heat pumps is that the energy from the exhaust air is insufficient to heat the house. As a result, an electric heating element is switched on. In the worst case, it’s so inefficient that you might as well have heated directly with electricity.

From the manufacturer of the mentioned device, I get the impression that the planning is generally reasonable and not completely flawed. Still, I would clearly prefer a conventional solution.