Cooling via underfloor heating with brine heat pump

hhmm. And the people who notice a scratchy throat without an enthalpy exchanger because the air is too dry usually only have this in winter, when the air outside is also rather dry?

The costs for the pump are roughly about €10/month, it is just a drop in the ocean in every respect.

The cooling capacity of underfloor heating is about 20-30W/m2. To effectively cool an average house, about 100 Watts/m2 are needed.

Power Consumption
Power consumption with passive cooling for me: <40 watts. Runs on average ~12 h/day. At my current electricity price of 27 cents/kWh, that is less than €4 per month. In reality, as a previous poster already wrote, you mostly cool during periods with a surplus of photovoltaic electricity, meaning it only costs me the feed-in tariff of about 11 cents/kWh, which puts us at under €2 per month for electricity... for me, that is "practically free" to operate.

Cooling Capacity
Is somewhere around 2-2.5 kW for us (which roughly matches your lower range, 20W/m², if I subtract the areas I don’t cool). This cooling capacity is absolutely sufficient with reasonable shading to keep the house at a consistently low temperature, even during longer heat periods. Of course, you cannot quickly cool down from 29 degrees to 20 degrees with it, but that does not correspond to our house concept either. Energy efficiency/sustainability ranked quite high; I do not want an air conditioner, but rather a cool home in summer if possible (not 19 degrees at 35 outside, but cool enough to live and sleep comfortably). Unfortunately, I do not have concrete core activation, which annoys me a bit in retrospect, because that would have made the whole system even more efficient.

@Dew Point "Issue": I have a sensor that monitors the dew point. I have had no problems with this during summer so far. The supply temperature is simply adjusted accordingly; even in the very rare cases where the supply temperature may only be max 19-20 degrees, the cooling capacity is still sufficient (okay, the power consumption of the pumps might increase by about 20 watts then, as the flow rate has to be raised because the temperature delta is smaller). There is a nice thread about this in the purple forum with statistics; unfortunately, I’m not allowed to link it, but everyone can google it.

hhmm. And the people who notice a scratchy throat without an enthalpy exchanger because the air is too dry usually only have this in winter, when the air outside is also rather dry?

Yes, only in winter and mostly only when the temperatures are around 0° (+/-5°) and below. Anything above that has a more pleasant relative humidity.

Of course, there are exceptions, and for some people it is simply always too dry.

@Dew point "issue": I have a sensor that monitors the dew point. I haven't had any problems in the summer so far. The supply temperature is adjusted accordingly

Where is the sensor installed? In the heat pump itself? What temperatures does it use for the dew point calculation? The temperatures of the individual rooms?

Where is the sensor installed? In the heat pump itself? Which temperatures does it use for the dew point calculation? The temperatures of the individual rooms?

We have a central sensor in the living area (the warmest and most humid area in our house, as about 90% of our daily life takes place there). The sensor is integrated into the control unit of the heat pump (we have a Stiebel Eltron WPL 05 cool). I checked the values once with a local measuring device, and apart from minor inaccuracies, everything is within limits. The control system assumes a safety margin anyway, so you are on the very safe side.

Oh yes, the cooling effect can best be understood in a vacation scenario: The house heats up slowly during absence, despite shading, of course. If I then activate the passive cooling about 2-3 days before we return, the temperature drops easily by several degrees (cooling capacity is naturally a bit higher here than in normal operation because the house is heated up and therefore the temperature delta is larger).

Okay good. And you practically not only recommend the "cooling" via the underfloor heating pipes but would accept the effort and costs (possibly a thicker concrete layer due to the statics and pipes + accessories for the circuit) of the [BKA] to make it even more efficient?