High costs for the heating phase due to incorrectly set heating device

Hello everyone,
I would like to describe my issue here and need your assessment.

We are currently building a single-family house with about 140 sqm of living space. The screed was poured in September last year. Afterwards, about 20 days passed during which the screed rested. Then the heating was started with a separate heating device. Unfortunately, the heat pump, which can also do this in our case, was not yet installed at that time.

The heating device, when properly set, has a heating program that starts at about 25 degrees, then increases by 5 degrees day by day and reaches its peak at 50 degrees. Afterwards, the temperature decreases again in 5-degree steps.

Our problem was that the heating device was set to manual instead of the automatic program. We noticed this relatively quickly because the temperature rose very quickly to 50 degrees and stayed there for three weeks. We reported this immediately to the construction manager and the responsible sanitary company. Unfortunately, nothing happened.

During the three weeks of heating up, we consumed about 5000 kWh of electricity. The heating up is the responsibility of the builder. That is clear to me. Comparative values from neighbors for the same house size are about 1700 kWh.

Now my question: Who knows of such cases and how did you handle them? Is it possible to hold the general contractor liable or withhold money from the final payment? How did you deal with this?

Our problem was that the heating device was set to manual instead of automatic program. We noticed this relatively quickly because the temperature reached 50 degrees very fast and stayed there for three weeks. We reported this immediately to the construction manager and the responsible plumbing company. Unfortunately, nothing happened.

What about your screed? Have you checked for cracks and similar issues?
Or is it now just about withholding money from the final payment?

In terms of content, action should have been taken directly in September...

Were your comparison values from the neighbor also achieved with "hotboy" or with their heat pump? That could explain the difference.

A colleague also heated via Hotboy, which would be 5,000 kWh for a similar house size. We had an external oil heating and used about 800 liters, which is similar cost-wise. If your kWh costs 25 cents, that's okay. At 40 cents/kWh, it looks a bit different, of course. But I also know stories of 14,000 kWh construction power for a major renovation, etc. If your screed hasn’t been damaged by continuous heating, I see little chance for you. Contractually, heating is hardly regulated, and it is therefore at the contractor’s discretion how they achieve the contract goal. That is why 98% of the time the costs for screed heating are passed on to the client—the contractor does not want any unpredictability.

A colleague also heated via Hotboy, which would also be 5,000kWh for a similar house size.

We had similar consumption for heating and construction dryers.

What does your screed say about it? Have you checked for cracks and the like? Or is it now just about withholding money from the final payment? Content-wise, one should have acted directly in September...

The screed is fine so far. Luckily, apart from the expected cracks, nothing has happened to it. Maybe that came across wrongly. Our heating device was set to "manual" instead of the automatic program. Due to the permanently high temperature of 50 degrees, we incurred higher costs than by using the automatic program. The neighbors had a similar device – no heat pump. In other words, the plumber set the device incorrectly, which caused me (higher) costs. We reported the incorrect setting immediately, as mentioned above. Unfortunately, nothing happened.