ᐅ Who should you entrust with the room-by-room heating load calculation?

face26 schrieb:

You’re mixing things up. This isn’t about sizing the heat pump, but rather about designing the underfloor heating system.
For me, the calculation took two evenings.
People waste more time on less useful things during house construction. But now I can show the builder that, for example, 30/25 works well.

The goal is to have an efficient heating system. It starts with sizing the heat generator and continues with designing the underfloor heating.
Why do you want to show your builder anything? What’s the purpose, what does it achieve?
Install 5–10cm (2–4 inches) spacing and cover as much surface area as possible. Then you can adjust the heating curve however you like.
That’s exactly my point—the calculation doesn’t have any practical effect during implementation except confirming that you should lay the pipes tightly and with good coverage, and that the smallest heat pump is sufficient. I’d argue this applies generally to all single-family homes up to 200m² (2,150 sq ft) with controlled ventilation. It’s that simple.

Don’t get me wrong, I also insisted my builder perform a heat load calculation because otherwise, he would have oversized the heat pump. And he didn’t want to take responsibility for a smaller one. So proof was necessary.
He did install the underfloor heating with tight spacing anyway; in the bathroom, I actually pushed for 5cm (2 inches) spacing and to include the shower area. It was just a cost issue—the pipes have to be paid for—but he didn’t resist.

And 10cm (4 inches) is sufficient for normal rooms. The only place where it could get too cold is the bathroom, if significantly higher temperatures are desired there.

guckuck2 schrieb:

The goal is to have an efficient heating system. This starts with properly sizing the heat generator and continues with the design of the underfloor heating.

Why do you want to show your heating contractor (HB) anything? What is the purpose, what does it achieve?

I agree with you that it’s about an efficient heating system.

Why do I want to show him something? Because not every heating installer is that flexible to accommodate all customer requests. Sometimes you just hear “that’s not possible.” I feel more confident when I have something concrete in hand.

As I already mentioned above, if you’re satisfied with a supply/return temperature of 35/30, then “your system” is sufficient. If you want to go lower, it really depends on your insulation standard and the rooms. For example, in my case, the children’s rooms upstairs only work at 30/25 with additional heating surface on the walls (high ceilings, large window areas).

In some hallway areas, in the basement, and so on, I don’t need 10cm of pipe coverage; 10cm would be far too much. So why should I install that much piping there?

Could this have been estimated in advance? No idea.

As I said, it cost me two evenings to figure this out.

As mentioned before, precise calculations are certainly not necessary just to get warm. However, if I want consistently low heating costs, I need to optimize the entire system by considering the following parameters together:

Supply/return temperatures
Flow rate
Heating capacity

If I then save 100–200 € in heating costs per year, why not?

The optimization and adjustment of heat pumps is currently more of an issue. No one really pays attention to it, and often even the heating installer isn’t focused on it. As frequently mentioned here in the forum and on Rosanen, the bathroom is almost always the problem. Even in our case, we’re missing about 1.5 degrees because an auxiliary heater was planned for, which was an error by Schwörerhaus. At the time, we weren’t aware of the real impact this would have. I didn’t pay much attention to it during the first few years either. After a control board failure in December, but thanks to the Rosa forum, I believe we’ve managed to achieve pretty good figures. Previously, annual consumption was around 5,000 to 6,000 kWh.

Daily consumption is about 25 kWh for a KfW70 energy standard and approximately 240 m² (2,583 ft²) of heated floor area. Assuming that January accounts for 25% of the annual consumption, the total would be around 4,000 kWh, which works well for us.

If anyone needs a contact for heating load calculation, in our case, it was the company Schuetz, which also supplies distribution panels, switches, and related components.

I also had my underfloor heating design done by an engineering firm I found through Ebay Classifieds. It cost me €180 for the room-specific heating load calculation, and I was satisfied with the quality.

Our energy consultant is offering us a heat load calculation. However, I’m not sure yet how detailed it will be. We found him through the KfW website. However, we are renovating, not building new. I’m curious to see how the heating system will work for us. We are using an underfloor heating retrofit system, which only allows for pipe spacing of 5cm (2 inches) and 10cm (4 inches), with no options in between.