Insulated old building from 1921: Conversion from gas heating

This is a heat pump vs pellet topic where I would prefer the heat pump. Less maintenance, no chimney sweep. But first you have to consider the feasibility: Do you have a way to read the supply temperature and the volume flow on your heating system? Are the new radiators type 33?

I found in my invoices: type 22 (predominantly) and type 12 were installed, nothing is noted for the bathroom radiator (it's one of those towel radiators).

Of course, I can ask about a heat load calculation, but based on experience, you hardly ever get a craftsman,

For that, please also do NOT use a CRAFTSMAN, but an engineering office (e.g. Heckmann).

One often reads that they are rather good in connection with underfloor heating and usually difficult to retrofit in old buildings.

I am renovating an old building myself - KfW55 - one apartment with radiators (type 33) and one with underfloor heating. Works well.

with them, the gas heating is completely off during the warm half of the year, the solar thermal system takes over everything.

It’s no different with the heat pump. You only need hot water. That costs me about 8 cents per day with the heat pump. You don’t need to spend tens of thousands of euros on solar thermal for that.

The flow temperature seems to be set to 75° if I am not too stupid to read it. Regarding the volume flow, I only find in the manual "Under the diagnostic point d.29 in the 1st diagnostic level, the volume flow on the heating side can be read with the heating pump running." The gas boiler is a Vaillant VSC 196/3-5 150 ecco Compact, if that helps.

The flow temperature seems to be set at 75°,

That is actually a temperature for an old building without any energy-saving measures.

Then I am either too stupid to read it or the specialist company is too stupid to set it up correctly. I consider both equally possible :cool:. I need to take a closer look at it in peace. A heating load calculation easily costs around 300€... that's quite a lot of money when you're just thinking about a conversion.

A heating load calculation easily costs around €300

You have to die some kind of death ;-)