Air-to-water heat pump sizing in new construction

Wouldn't it be easier to contractually stipulate: "all rooms 10cm & bathroom 5cm"???

No. That's just run-of-the-mill again. It is properly calculated and designed. Anything else is virtually botched work or a "We've always done it that way." Who tells you that a) the desired temperatures will be achieved or b) the heating system will even get a reasonable hydraulics with that?

No. This is just the usual routine. It is properly calculated and designed. Everything else is basically botched or a "We've always done it this way". Who tells you that a) the desired temperatures are reached or b) the heating system even gets reasonable hydraulics with it?

So it's more complicated than expected after all. :(

Well, I also think highly of a good design of underfloor heating, but I am still not a fan of the partially made calculations. Often, too much emphasis is placed on some details (floor coverings, desired temperatures, ventilation systems, ...) and calculations are made down to the last decimal place, while other aspects (that floor coverings can also change or that there might be a carpet on top, furniture, waste heat from appliances, solar gains, and the fact that no significant differences can be achieved within the thermal envelope) are completely ignored. I have also dealt with this a lot myself and calculated to see which change has which effect.

With such basic rules, which can then simply be expressed as wishes and also checked, in my opinion one often fares better than with "over-optimizing":
- approximately equally long circuits (small rooms like guest toilets, corridors, and storage rooms often pose a problem. Here one can try to combine them)
- no circuit longer than 100m.
- manifolds not in places where it should not get warm, like the bedroom or pantry
- no more than 15cm spacing.
- smaller spacing in bathrooms
- ideally lay pipes on an exterior wall in bathrooms (often the warmest room with the smallest heating area due to often omitted bathtubs and showers) because more surface area brings much more than smaller spacing.

In my opinion, with such basic rules that you can simply state as wishes and also check, you often do better than trying to "over-optimize":
- approximately equally long loops (small spaces like guest toilets, hallways, and storage rooms are often the problem. Here you can try to combine them)
- no loop longer than 100m.
- distributor not in places where it should not get warm, like the bedroom or the pantry
- no more than 15cm spacing.
- smaller spacing in bathrooms
- ideally cover an exterior wall in bathrooms (often the warmest room with the smallest heating surface due to frequently omitted bathtubs and showers) because more surface area brings much more benefit than smaller spacing.

As a basic prerequisite not bad except for one point. The spacing should not exceed 10cm. 15 is no longer up to date.

So, since a window has now been omitted in our case, we need 45 watts less heating load in the living-dining room. Therefore, I had the design updated again and also worked on the large overlap. This is how it looks now.







I now see this as a concession to the heating installer so that he can install much more comfortably on the ground floor. Fewer heating circuits and significantly larger laying distances.

An impressive note from the engineering office was also that I should definitely pay attention to the compliance with the surface/laying distances on the upper floor. Especially the wall heating in the upper floor bathroom.

you really know your stuff and are currently supporting . You are also currently discussing the pressure losses and the flow rate of the pump. Does this look unusual here?

I hope that when it finally starts soon, and I can begin the thermal balancing, I will be as much of a pro as you. I already see myself optimizing the heating curve and flow rates for weeks in winter.

Would it be possible to get your Excel sheet as a template? That would be great :)

As a basic requirement, not bad except for one point. The distance should not exceed 10cm. 15 is no longer up to date.

Well, in my calculations, for example in "Living Dining Kitchen," it didn't make a difference, which already covers a large part of the house.
I simply already had more capacity than needed. Making it even tighter led rather to problems with long loops.

In the bedroom and storage rooms, 10 doesn't make a difference either.
Bathrooms were already called "tighter" anyway.
That leaves a few hallways and the children's rooms.
You can do 10 there, you can also leave it at 15, maybe I'll play around with that again tonight to specifically determine what it really makes. ;-)