Gas heating new building - Is solar thermal necessary for hot water?

They know that they have to submit the energy calculation with the building application. They also roughly know: If the house is such and such, the heating must be such and such, otherwise it won't work.

Then you are forced to add solar thermal to the gas heating, although a more creative expert could manage without it. (At least that was the case before the last energy saving ordinance amendment, I am not up to date, but in borderline cases it can be worthwhile to have an expert do the calculation rather than have the general contractor do it roughly with "we've always done it that way.")

I specified gas condensing boiler, underfloor heating throughout the house. As manufacturer of the gas system, I favor Viessmann or Junkers. Nevertheless, the performance and equipment of the system is not described in the offer

I would also specify the flow temperature, from which the cost-relevant laying distance results (preferably as low as possible).

Unfortunately, as a layperson, I cannot estimate the supply temperature or the installation spacing. Nothing is described about this in the construction service description.

Wikipedia: For use in connection with heat pumps and/or solar heating support, surface heating systems are suitable, which only require flow temperatures of about 30-35 °C.

Just ask the GU what he has planned. Alternatively: consult an energy advisor.

You do not specify the installation spacing. You only say, build me a heating system (underfloor heating) that works with a maximum flow temperature of XX °C (e.g. 30 °C)*.

Just so that you don't get a "low temperature technology" with a flow temperature of 55 °C and could never ever use a heat pump.

* Under design conditions (depending on the region).

Hello,

Unfortunately, as a layperson, I cannot estimate the supply temperature or the installation spacing. Nothing is described about this in the construction performance specification.

As a rough rule of thumb, you can assume 15 cm installation spacing in normal living areas and 10 cm in bathrooms.

If in living areas the pipes are laid even closer, you can quickly run into problems with the maximum length of the heating circuits. And then suddenly you have several heating circuits in each room, which of course drives the costs considerably!

Best regards,

Andreas

My opinion. I would not invest more than technically necessary here. What matters is a well-insulated, airtight envelope without major heat losses. They all build that. Then the savings with a low-temperature heating system compared to a standard one will be so minimal, in euros and cents, that the extra effort is not worth it. Junkers/Viessmann, 5 or 6 sqm of solar on the roof for hot water and because politicians think it's great, bam, done. Better spend your money on a nice garden. Karsten

Junkers/Viessmann, 5 or 6 sqm solar on the roof for hot water and because politics think it's great, done

So far solar thermal is not planned, but the calculation has not yet been carried out. The general contractor wants to do this only during the building permit application. If not necessary, I would like to use the money for other purposes.