Individual room control with air-water heat pump and underfloor heating

For the cooling function, however, it can be useful. However, I do not really consider the few degrees possible as real cooling but at most a slight tempering. Everyone has to decide for themselves whether it is worth it.

What would be the alternative? Is cooling (even if only by a few degrees) possible without ERR? Presumably yes, but too energy-intensive?

When cooling, you usually want all valves fully open. In our office, the building services are messed up and the thermostats block the cooling. Accordingly, we go through once in early summer and turn all valves manually on (=no control), then back to automatic in autumn. You obviously can't compare the effect with a proper air conditioning system, but especially overnight it does pull out a few degrees.

And you spoil your rooms with small dust catchers on the wall. I would leave them out and set myself free.

I would simply leave them out. Who wants to see this liberation...

What would the usage profile look like then? In winter, everything set to "manual off" as described by Michert, and in summer just regulating down the room to be cooled? With "manual off," the other rooms would also get the cool water?

With cooling, or better: tempering – because it is really only a few degrees – you have to make sure, for example, that it does not get too cold. Otherwise, you quickly get problems with moisture (condensation) and then mold. The keyword here is: dew point. Also, there are some people who find a too cold floor unpleasant. Therefore, control may make more sense here than with heating.

I would simply omit them. Who wants to see this exemption...

When we talk about a house networked via KNX, you can always refer to a central control system in case of doubt. I would definitely always avoid the ugly individual thermostats in the rooms.

I would definitely always do without the ugly individual thermostats in the rooms.

Since a KNX house usually implies a more or less well-thought-out plan or even a concept, this question does not even arise. The temperature sensors along with the thermostat are integrated into the touch sensors (room controllers), and thus with KNX you have the ERR included. Of course, you still need the counterpart with the actuator and the valve heads.

Additional individual room thermostats would make the whole project absurd with KNX and are normally not installed.

What would be the alternative? Is cooling (even if only by a few degrees) possible without ERR?
Probably yes, but too energy-intensive?

Yes, of course cooling is possible without ERR and is also not too energy-intensive. It’s just that there is little benefit both with and without ERR, because the capacity is low. Due to the mode of operation in the floor and not where cooling is actually needed or required.