Looking for a cooling solution. Underfloor cooling?

We already had a small discussion on the topic this week in the construction costs thread, but I want to take it on my own now. Originally, we weren’t sure if we even wanted cooling, but since we’re already having another "summer of the century"... I definitely want to have a plan for it. The following key data:
- northwestern hinterland of Lake Constance at 660m
- KfW40+ monolithic with brine-water heat pump, 2 full floors with attic, both floor ceilings made of concrete
- shading is planned, almost all rooms have windows with different exposure so you can shade without sitting completely in the dark
- I will mostly work from home (and home office in the garden is not an option).

How much cooling demand we will have is still unclear. Compared to the current situation it will certainly improve significantly, due to the altitude, distance from the lake and loose development it will be less hot and should also cool down much better at night. The aim of the whole thing would mainly be to eliminate the peaks, permanent air conditioning at 22 degrees is not the goal. 25-26 degrees during the day are also acceptable.
Basically, I also think that with appropriate shading we are not badly positioned at all, the roof should prevent heat from pressing into the living area.

We have had underfloor cooling in the office for a few years now and because of the brine-water heat pump that can actually be implemented quite efficiently, so that was our first approach. Unfortunately, the cooling cost has risen from 2k to a good 4k compared to the original offer. That’s a bit too expensive for me. Therefore, the next idea was to simply get one of the portable monoblock air conditioning units and somehow seal the hose at the window. You should be able to get a pretty good one for well under €1000. A split air conditioner would of course be smarter, but that would require a core drill (expensive) and I’m unsure where it could even go. Ideally, you would put it in the corridor upstairs, but there we have a large fixed glazing in the stairwell. If then, it would have to go in a corner of the study (child 2 in the plan), where the architect has drawn the bed. But then we would only have cooling in the study. And is that even that simple in an energy-efficient house or would I get problems with the KfW (keyword deterioration prohibition)?



Currently, I’m tending towards the mobile solution because it is cheap and flexible. Opinions or questions?

In a project with estimated total costs well over 500k, you want to install a "makeshift solution" due to a 3k difference. Just think about whether you wouldn't find that "crazy" as an outsider? My decision would clearly be either air conditioning with core drilling or PassiveCooling via the ground source heat pump.

That's why the next idea was simply to get one of those portable monoblock air conditioners and somehow seal the hose at the window.

Really bad idea. You wouldn't constantly drive around with a spare tire either. It's only meant for the way to the workshop.

A split air conditioner is the simplest, most effective, and efficient solution. A core drilling for it usually doesn't matter at all. It doesn't have to be a 200mm hole in the masonry.

In an object estimated to have total costs well over 500k, you want to install a "makeshift solution" because of a 3k difference. Think about whether you, as an outsider, wouldn't find that "crazy"? My decision would be clearly pro either air conditioning with core drilling or PassiveCooling via the ground-source heat pump

And above all, why only now, when the train has almost left the station? Why even ground source at 40+? An air-to-water heat pump would have done the job too. For the saved drilling costs, then "real air conditioning," if necessary.

So
You can definitely forget about mobile ... Super loud and inefficient ... that's really only for an absolute emergency.

You want to install a "makeshift solution" in a project with an estimated total cost well over 500k just because of a 3k difference. Just think about whether you wouldn't find that "crazy" as an outsider?

Probably yes. And of course, 3k more in a project with a total budget of 550k (all in with kitchen, land, additional costs...) is not huge. On the other hand, I have the feeling once again that the planning costs are running away. Something for the cooling here, more in the bathroom there, the garden is more elaborate (partly voluntary, partly because of the terrain) and more expensive than calculated. Heating the screed is currently still incalculable. Tiles and floors will arrive the Saturday after next; I certainly won't get them at the prices from 1.5 years ago anymore... and so a lot adds up... there is still some buffer left but I don't want to use it if I have the option not to.

And above all, why only now when the train has almost left the station?

Air conditioning was not really a priority for us and there was always the option of floor cooling if we decided to go for it. I would have taken that now as well, but I don’t like the price anymore.

Why even brine (ground loop) at 40+? An air-to-water heat pump would have done just as well. For the drilling costs saved then "real air conditioning," if needed.

The general contractor installs that as standard and I was happy to take it. Yes, financially it certainly wasn’t the ideal solution but back then there was also BAFA funding so the extra cost wouldn’t have been as high as now and I also found that much more appealing than the 40,000€ BAFA-eligible air-to-water heat pump that everyone else wanted to sell me. Today I would probably plan it differently. But in that regard, the train has also left the station, the drilling was done at the end of May. Back to the split air conditioning that you all vote for... what would be a realistic price under current conditions? And would there be problems with the KfW because of that? How much more expensive would it be if you postpone it and retrofit it later? We are currently in the rough installation phase between the electrician and heating/plumbing. The electrician is almost finished and said he will do the rest after plumbing. That is also a problem because the decision would have to be made quickly in case of doubt.