Reversible Air-Water Heat Pump vs. Air Conditioner with Heating Function

What are the key data of your house, especially the insulation standard? This topic is very individual, also because everyone has a completely different perception regarding heat or temperatures. Some people are bothered by a slight draft, others by the noise of a controlled residential ventilation system, and still others by the too cool air from the air conditioning, and much more. A single opinion will not be able to help you here; there is always a lot that can be done and also lived with. However, every solution has its peculiarities and advantages and disadvantages, which you ultimately have to weigh up for yourself. Therefore, more input would be needed first about what is important to you, what you like and what not, or what your current thoughts for or against something are.

The insulation standard is between KFW 40 and 55. Timber frame construction. It is indeed very individual, but I am trying to fight my way a little through the jungle. The perception of cold/heat is one thing, but I can estimate that well. Therefore, I try to keep the questions as general as possible: Namely, whether you will feel a draft? I have meanwhile heard about so-called "wind free" systems. Maybe there is specific experience with that.

What is important to us:
- Air conditioning. Cooling by 2-4 degrees is not sufficient.
- Also, we do not want cold feet (e.g., through the cooling function of an LWW)
- warm air is generally perceived as pleasant, never had underfloor heating before, so it is not "missed" per se.

What we definitely do not want:
- Sitting on the sofa and feeling a draft (whether heating or cooling)

Possible issue:
- The living-dining area is about 50 sqm. Possibly a more powerful device will be needed for this, which logically will have a stronger airflow. (or for example, two devices could be used in the large room)

Cost issue:
We have two offers. One for classic underfloor heating + ventilation system = 62,000 EUR; One for LLW with ceiling cassettes = 40,000 EUR

Huge difference for - logically - the exact same building.

Big difference for - logically - the exact same building.

But completely different technology. A well-designed controlled residential ventilation system, which for example does not have the air outlet directly above the sofa, you will not feel or only when you have the party mode on.

Climate = draft. You will not be able to avoid that because this is simply the nature of the heating. Warm air (or cold) has to be blown into the room.
Underfloor heating and controlled residential ventilation = with correct design no noticeable effect (except fresh air and warm room), but no cooling function as you desire is possible.

What you want as an all-round solution can at best be achieved through a component activation = concrete core activation. Especially strong cooling will typically always result in a draft.

I would basically be interested in the topic as well.
I would appreciate the correction of my thoughts (or possibly also the approval – although I don't really believe in that):
- Ventilation systems are now almost a quasi-standard in new buildings. Can't I use an air-to-air heat pump here and additionally cool/heat and use the existing infrastructure (or, if the pipe cross-sections are too small, adapt the infrastructure cheaply if you are still in the planning phase)? Or am I so far away from practically usable infrastructure for cooling/heating that it simply isn't practical?
- I could even retrofit this air-to-air heat pump if I initially shy away from the investment and first want to see if it can work without it because the shading is well planned and enough thermal mass is built into the house to avoid strong overheating (+ slight cooling effect through ventilation and bypass at night)
- since I would need hot water generation anyway with an air-to-air heat pump, I thought of an air-to-water heat pump. I was thinking of a very minimally sized air-to-water heat pump with underfloor heating, which could even slightly support cooling in summer, take over hot water generation, and largely cover the heating function in winter

So basically, initially a normal system with a ventilation system and air-to-water heat pump (including underfloor heating) that I could possibly expand quickly and cheaply if needed with the air-to-air heat pump.

- Ventilation systems have become almost a quasi-standard in new buildings by now. Can't I use an air-to-air heat pump here to additionally cool/heat and use the existing infrastructure (or if the pipe cross-sections are too small, adjust the infrastructure cheaply if still in the planning phase), or am I so far from suitably usable infrastructure for cooling/heating that it just isn't practical?

Ventilation and heating are different techniques. Not every room in a controlled residential ventilation system gets exhaust and supply air simultaneously. So the directions don't match either. Also, the volume flows are different. What exists now are additions to controlled residential ventilation systems, such as, for example, one with 2.5 kW cooling capacity - but these also have their price and require a suitably designed controlled residential ventilation (insulated pipes, minimum volume flow, or similar).

- I could even retrofit this air-to-air heat pump if I initially shy away from the investment and first want to see if it can work without it, because the shading is planned well enough and there is enough thermal mass in the house to avoid strong overheating (+ slight cooling effect through ventilation and bypass at night)

See first answer.

- since with an air-to-air heat pump I would anyway still need hot water preparation, I thought about an air-to-water heat pump. I thought of a very minimally sized air-to-water heat pump with underfloor heating, which can even somewhat support cooling in summer, handle hot water preparation, and take over most of the heating function in winter

If you heat with an air-to-air heat pump, you need a hot water heat pump. I understand the second part of the quote as you basically want to install two heating systems. So basically a car with a gasoline and additionally a diesel engine, both able to work alternately.

Thanks in advance for the answer! That is more than a proud price :O
Yes, the question arises whether the rooms with supply air are also exactly the rooms I want to cool? I would say, mostly 'yes'.
Therefore, I see this more as a minor problem, because especially the living and common rooms are usually supplied with fresh air (I had even thought about that, just didn’t write it down – but definitely a valid point and maybe not as true for everyone as it is for me).
Insulated ducts is a very good point! Thanks
Then the question arises with which volumetric flow rates one can achieve how much cooling capacity, or in plain German 'how much cooling capacity can I achieve with the volumetric flows that I can use sensibly in the controlled residential ventilation'.

The last point is rather meant like 'I want the air-water heat pump because it is the base of the house, if I have the air-air heat pump I can use it additionally to relieve the air-water heat pump or move it into efficiency-optimized areas'
so more comparable to a hybrid – although I’m not a fan of hybrid cars at all.