Heating replacement in old buildings - gas or air heat pump

???? What noise? From the heat pump? That's a rumor. Isolated cases yes – just as there are isolated cases where indoor units make noise (a gas heating system also makes noises).

As I said, I have only been dealing with the topic for a few days. I wouldn’t have thought before that underfloor heating in combination with an air-to-water heat pump makes sense in an old building. I just browsed the internet and came across the limit values.

Definitely keep the gas boiler. It will save you if the conditions are not 100% optimal for a heat pump. For example, on cold days or with sudden demand for hot water. Especially if additional insulation is not planned.

I would also keep the gas boiler. But not because the heat pump doesn't make sense (the house is insulated except for the façade insulation), but because I do not want to replace a nearly new gas heating system for cost reasons.

That makes it even more difficult.

I would also keep the gas boiler. But not because the heat pump doesn't make sense (the house is insulated except for the facade insulation), but because I don't want to replace a like-new gas heating system for cost reasons.

It may be that in this individual case it is still worth it due to the subsidy. May, so it does not have to be considered an argument. In this case, however, I would also keep it and design the underfloor heating so that the lowest possible supply temperature is sufficient. So have it designed according to the room-specific heating load calculation. Then you can still switch to a heat pump later. But you don't have to.

So if a heating engineer makes me such a proposal, I would expect him to be able to calculate exactly that it is also worthwhile for me. Otherwise, I would get an offer from a second heating technician and ask for his recommendation. The [Gastherme] is really still practically new, and personally, it would hurt me to dispose of it or sell it for little money.