Is underfloor heating in the basement useful??

There was an attempt somewhere here last year on the topic of heating the basement. The result was that you can save a significant amount of money on heating costs if you don’t heat.

It’s somewhat logical when you consider that warm air rises and lower temperatures settle in the basement without heating. The heating circuits on the ground floor then naturally need more flow to compensate for the missing output in the basement.

We heated half the basement, but with underfloor heating. Under no circumstances mix! Although I couldn’t see whether it was a heat pump, district heating, or gas, in all cases the flow temperature must then be lower since you don’t have to heat the radiators.

It is somewhat logical if you consider that warm air rises and lower temperatures settle in the basement without heating. The heating circuits on the ground floor then naturally need more flow to compensate for the missing output in the basement.

Warm air only rises if it is colder above. Basement 19, ground floor 21° --> Nothing rises there. And if you need higher flow rates and/or higher temperatures upstairs, it is simply not more economical than heating the basement right away. The goal of surface heating systems is ALWAYS to have the largest possible surface area in order to require as little temperature as possible. The unheated basement only works if it is not part of the thermal envelope. But for that, it must be properly insulated from the ground floor. Nowadays, that can no longer be desired.

Since radiators require completely different supply temperatures than underfloor heating, one should definitely not combine both.

I don't see any technical problems there. Of course, radiators (multi-layer flat convectors?) would have to be sized larger for the same heating output. But in the basement, a lower temperature level is usually sufficient.

Conversely, I see rather higher heat losses with underfloor heating in the basement, as very few basement screeds are well insulated downward. Furthermore, I have concerns about heated screed in the basement, as heavy components tend to be placed roughly on the floor there, which in my opinion increases the risk of cracks in the screed structure.

My impressions are based on problems in the family, who have already had to tear up their heated screed twice to renovate it.

If you have the space to install huge radiators in the basement, the temperatures are largely irrelevant (so you don’t just increase the temperature for the basement), and the plumber can calculate it properly so that the resistance in the radiators is similar to that of an underfloor heating circuit, you can do it. It would be too extreme for me and I would rather not sacrifice wall space in every "storage room".

On the other topics: Nowadays, properly insulating a basement should be a given. In a few years, there will only be heat pumps and you are building a new house, not an old one. And I can’t imagine what it would take to smash a proper 7cm heated screed with (probably) tiles in the basement...

Thank you for your help

so we have local heating and the regular radiators would be run at 60 degrees

For the underfloor heating, the basement floor will be specially insulated again according to the developer

How much can such a heated screed withstand?

If it is properly executed, anything a floor is subjected to. Here in the old building, due to the limited installation height and the load-bearing capacity of ceilings, I have a screed thickness of 3.5 to 4.5 cm. So much thinner than usual in new buildings. And even here we live completely normally...

Regarding the local heat supply: You should expect that this heat source will eventually run out, since no fossil fuels will be allowed to be burned anymore. At the latest then, you will be glad to have a heating system that does not require more than 30° supply temperature. Even now, local heat supply (usually) is one of the most expensive ways to heat a house. But probably you have no choice, right?