Underfloor heating and air-to-water heat pump in new construction: am I going to have problems?

It is important in the return flow, meaning that the buffer is not heated first and then the underfloor heating is heated from the buffer, and that it is not too large.

I wouldn’t say it that generally. What’s important is the return flow, meaning that the buffer is not heated first and then the underfloor heating is heated from the buffer, and that it’s not too big. If the buffer is several hundred liters large and is on the supply flow, it’s really crap. Regarding not being able to change it: If the buffer is on the supply flow and you can’t convince the heating engineer to do it differently, you could try what I unintentionally managed: Ask so many questions and keep insisting until the heating engineer throws in the towel in frustration. Then it’s not your fault, you can find your own (or the general contractor has to find an alternative), but actually the general contractor can’t then demand that you also have to arrange all the subsequent trades yourself. But beware, this can mean significant cost increases and delays. So this is only a recommendation for an emergency brake...

The buffer is to be fed with 200l into the supply line. That is the specification from Viessmann.

I will agree with the general contractor that I will nail him down to - house gets warm - max. 4-5 cycles per day in winter - annual performance factor > 4.5 (calculated is 4.9)

Terrible :mad: You can understand the installers if the manufacturers make such requirements.

Sounds like a clause he probably won't accept, but good luck and please report back!