Costs for the heating & sanitary trade

Hello everyone,

I have finally received an offer from a very interested company (around the corner from the construction site) that is not an intermediary.
The total amount is actually quite interesting. There are only a few items that I don’t fully understand, especially a buffer, but for the water storage tank. On the one hand, people say buffers are always bad, but on the other hand, as far as I know, that refers to buffers for the underfloor heating. Here it is for the uniTower, so the domestic hot water tank. Maybe not so bad after all?
It is supposed to prevent the heat pump from switching on too often. So actually the opposite of what is usually criticized about buffering here. I am only skeptical because in the description of this buffer in the various shops where it could be purchased, only the Arotherm Split is mentioned as the compatible heat pump. There is nothing about the aroTherm Plus.
Well, I will definitely question the installer about this.
The descaling system is missing, but partly my fault because I wrote about it in the first email, but forgot it in the "tender".
Under insulation is missing – does anyone know what something like that costs? About 82m² 10cm on the ground floor and the same again 8cm on the upper floor.
Circulation could maybe be omitted...
He apparently wants to put ventilation valves partly into the floor now; I don’t know if the execution planning still allows that.
Question to the group: does that fit from your point of view?
I will also inquire whether he can shift the cost weighting more toward the heat pump and controlled residential ventilation since I still have some funding amount "available."

Below is the offer:

I can say little about the technology but don't you want to have the riser pipe installed IN the wall for the two showers so that only one outlet comes out at the top, where any showerhead or similar can then be attached. I don't like unnecessary rods. Just an idea...

I thought I was flexible especially with plaster because the different [Unterputz Systeme] are not necessarily compatible. And then there is also the cost issue. Sure, it would be nicer.

hm, for us here currently that was no problem and it actually shouldn't be much more expensive, as long as he only charges for the effort. Of course, it requires a built-in fitting but then it's just a piece of pipe going up built-in. Yes, not all systems fit everything but as long as you stick to the usual suspects that fits. We don't necessarily have fancy models here, but Grohe or Vigour or similar, something was just installed without asking. Nevertheless, all sorts of things fit, e.g. overhead showers from Grohe, cheaper and others as well. I would take a closer look at that. Maybe you can save something elsewhere too, e.g. taps or wherever, it's just as always a matter of preference.

I would keep circulation in, it is comfortable, possibly a second garden tap, such a house is quite large outside and the irrigation controller would have its fixed place. Check the datasheet of the outdoor unit of the heat pump for sound pressure less than 35dB and have it installed away from bedrooms.

Circulation is definitely good, however the distances are never particularly far for me. Both bathrooms and the kitchen border the utility room. I think the water from the storage tank arrives quite quickly everywhere. A second outdoor faucet, on the other hand, is certainly not cheap because on the side where it would make sense I don't have any other water supply, so I would probably have to have about 15 meters of piping installed just for the outdoor faucet... But I will inquire about it. The heat pump is the same as the one I would have with the GÜ user, so it has already been thoroughly tested. The installation location is also suitable.