Underfloor heating on the ground floor and upper floor, radiators in the basement?

Hi everyone,

no fighting please...

Bauexperte is certainly right when they recommend more insulation, it doesn't hurt at first. The real additional costs for 120 mm instead of 100 mm are almost unnoticeable if you look at the cost of the material. The work is basically the same, whether you stick 100 mm or 120 mm boards on the wall. But craftsmen always love to charge mercilessly for such things, the actual additional effort usually bears no relation to the calculated extra costs. In other words, they charge an arm and a leg...

I have also painfully learned that my negotiating position is now significantly worse than I’m used to from my job. Suppliers who try to play such games are allowed to finish their coffee with me and are then politely shown the door. There’s already someone waiting to do the job. However, I also award significantly different amounts of money there.

: If I understand correctly, you suggest running the heating itself at a higher flow temperature (e.g., 50°C) and then splitting the output – one part goes as 50 °C to the radiators in the basement and the other part I mix down with the return flow to say 35 °C for the underfloor heating on the ground and upper floors. That is this three-way mixer?

That would solve the problem quite elegantly and above all simply...

Best regards,

Andreas

Don't get that wrong - 20mm more would have cost us about 500 euros more (and that with self-installation without material through the contractor).

It doesn't sound like much, of course, but you first have to recoup that through lower heating costs with 100mm - you probably won't experience that. Therefore, a critical consideration of some insulation should definitely be allowed.

Hello Andreas,

: If I understand correctly, you suggest running the heating itself with a higher flow temperature (e.g. 50°C) and then split the output – part goes as 50°C to the radiators in the basement and the other part I mix down with the return flow to say 35°C for the underfloor heating on the ground floor and upper floor. Is this the three-way mixer?

That would solve the problem quite elegantly and above all simply….

I am an ambitious saleswoman; not a heating expert.

Since I don’t know the correct term for the "mixer" (for me it just has to work), I quickly googled (information can also be found at the popular general store Bosy here) and found the following on the topic:

**"Regardless of how the rotary slide of a heating mixer is adjusted, two mixer types are distinguished: the three-way mixer and the four-way mixer.

In the three-way mixer, cooler return water is mixed with the warm water from the heating boiler. This lowers the temperature in the heating flow to the desired value. The three-way mixer does not directly influence the boiler return temperature.

In the four-way mixer, the heating flow temperature is lowered and the boiler return temperature is raised simultaneously. The latter happens by mixing hot water from the boiler flow according to the position of the rotary slide. The four-way mixer creates two circuits in the system schematic: the boiler circuit and the heating circuit. The property of the four-way mixer to raise the boiler return temperature, however, is unfavorable in heating systems with condensing boilers. Condensing boilers achieve particularly high efficiencies when the return temperature of the heating water is below the dew point temperature of the water vapor contained in the flue gas (approximately 47 °C for oil firing, about 57 °C for gas firing). This allows a large part of the water vapor in the flue gas to condense and the latent heat released can be used as additional heat. When using a four-way mixer, the raised return temperature (depending on the boiler load) can be temporarily or even constantly above the dew point temperature of the flue gas. The condensing effect is prevented. For this reason, a three-way mixer should be used when a condensing boiler is employed."

Source: SBZ Monteur SHK Magazine

HTH

Best regards from the Rhineland

Uuuih, you're right, going from 100 to 120 mm is indeed a real jump, I hadn't even noticed that. Thanks for the tip! That amounts to a good 400 € for about 100 sqm of wall to be insulated. *Astonished* The guys will probably charge 1500 € for it. I think you then have to look at the building physics in detail (which wall thicknesses you have made of which material, where the dew points are, temperature gradients, etc.) to decide what makes sense. Economically, you probably won't get the 400 € back. But after all, house building is not about profitability.... Best regards, Andreas