Underfloor heating, room thermostats and cold tiles

Hello Stephan,

@ypg Yes, but according to my understanding there must be a heat flow to maintain the 20° as well, because the reaction time of the underfloor heating is quite slow, so "switching off" or for the room upon reaching the temperature is pointless. I am only surprised now that although there should actually be a flow, the floor is ice cold.

At first, I am puzzled that you expect it to be warmer inside than outside with an outdoor temperature-controlled heating system. And furthermore, that you have set the bathroom temperature similarly low as the living rooms; personally, that would be too cold for me – energy costs aside.

Only with falling outside temperatures will you feel the heating through your feet... but hardly at a set 20 degrees.

Rhenish regards

We set our thermostat to 14 degrees in the summer. Nothing happens with the heating, it stays cold. Also at the beginning of September, of course (outside temperature around 15 degrees?!)

Now we set it to 19 degrees, because in mid-September it was a bit cold in the evening, plus the tiles were cold and therefore "unpleasant."

Now it is around 17-18 degrees outside, and the heating stays cold - nicely economical. Because inside there are 19 degrees.
If it becomes uncomfortable in the evening, the thermostat is turned to 20/21 degrees so that the heating kicks in and floor heating is available.
Constantly in winter, we basically set it higher from 4 p.m., then the warmth is present throughout the whole day.

Thanks first of all for the answers. The main reason why I’m asking is not my personal comfort, but the fact that I don’t really trust these thermostats regarding their functionality. That’s why I phrased it somewhat neutrally at the beginning, I just wanted to hear opinions, it could be that I am completely wrong. Three of them have already been replaced because they caused unpleasant noises, and as for the rest... I have now turned the one in my bathroom to 30°, whether that makes sense or not, but I want to see if anything changes. As for the outside temperatures, here it hardly goes above 10° once the sun is gone, at night around 6-8°, so you might think that the heating kicks in. Well, it’s not cold in the rooms now, but as I wrote above, I’m testing it in the bathroom, turned it up last night, this morning there was still no difference to note, let’s see how it looks this evening. Regards Stephan

Hm... I have learned that it is best not to turn off the FB heating during the summer either. The system should actually regulate itself. Then you should also feel a slight warmth on your feet in the morning at lower temperatures during the night (especially in the transition period). At least, that is what I would expect.... I am curious to see how it turns out for you, Stephan.

A thermostat is meant to maintain the desired warmth in a room. Once the set temperature is reached (without considering hysteresis), the heating surface does not need to emit any heat. If the set temperature is undershot, your heating surface will emit heat. With today's insulation standards and the design of underfloor heating, you will hardly notice any difference in the borderline area. You also have to consider the transmission losses, which are no longer that high in modern houses (in your case with KfW70 already quite decent). Your argument that it is already cool at night would be relevant if it were consistently quite cool. Your house would have to be completely cooled down first. At the moment, however, it will still warm up during the day and release that heat at night.

If you don't trust the thermostat, then buy a thermometer and see if the 20°C is always maintained...

A thermostat is, after all, meant to maintain the desired warmth in a room. Once the set temperature is reached (without considering hysteresis), the heating surface does not need to emit any heat. If the set temperature is undershot, your heating surface will emit heat.

Correct! The target parameter is always the room temperature to be achieved/desire d. Not insignificant in terms of comfort and energy efficiency is comfortable control. Sensibly, there are several nested control loops (hierarchy) for this purpose. Usually:

- Outdoor temperature-controlled system flow temperature (heating curve, primary)
- Room temperature for underfloor heating (ERR), for radiators ThV
- System return temperature control (performance modulation of the heat generator, mass flow adjustment of the heating circuit pump)

as stated above.