ᐅ Design of Underfloor Heating for a KfW 55 Energy-Efficient House with a Ventilation System

dream2023 schrieb:

We’ll go through everything again there. Downstairs, there’s still some flexibility with the pipe lengths, and in most rooms we could manage without additional heating circuits. Upstairs, it’s really tight aiming for the 100 m (330 feet).

I predict this will become the problem. Downstairs, in my opinion, it will always be warm enough. The ground floor alone, with TV, cooking, baking, and regular occupancy, heats itself “automatically.”

With this standard design, you will definitely get a bathroom that’s too cold. For example, I have three heating circuits there and it still remains too cold—especially if you’re already undersized at a 35°C (95°F) design temperature. This was our planning: https://www.hausbau-forum.de/threads/luft-wasser-waermepumpe-dimensionierung-im-neubau.36049/post-443195

The general contractor doesn’t care—it’s not a warranty issue. The building will get warm. However, you will then have to turn up the heating curve so that the bathroom or other critical rooms get warm. The consequence is that you have to throttle back the other heating circuits so you don’t end up with 25°C (77°F) in the living room. Then the heat pump runs inefficiently, like a “bag of nuts.” Even a new or more modern heat pump won’t fix this in 15–20 years. That is a permanent problem.

That’s why it’s worth the effort now to discuss this in detail down to the last point.

OWLer schrieb:

That’s why it’s worth the effort to discuss it thoroughly down to the last detail.

If the other party is even willing to go along with that. More likely with individual trades than with a general contractor. But you’re right, in my opinion this topic is too often given too little attention during planning, which cannot be significantly changed later on. That’s why I don’t understand how, for example, a general contractor can be so “indifferent” about it.
You don’t expect anything for free, you just want to make sure that the optimum efficiency and cost-effectiveness have been achieved. Having to dig around just to get any information is really frustrating…

Hello,
the first mistake is already in the contract setup with the general contractor. If it is not clearly defined what exactly the heating trade is responsible for, you will be in a weak negotiation position after signing.
I still wish everyone good luck with the negotiations. Maybe you can get the heating technician involved early and negotiate something directly. That’s what the technician did for me. He put the manufacturer’s calculation aside and implemented my own calculation. The site manager didn’t notice, as he was not present after the initial planning meeting.
Best regards

Hello everyone,

As the original poster, I wanted to share an update on the current status.

We managed to have the heating manifold on the upper floor replaced with a larger one, so now we have the option to install two radiators in every room upstairs.

Thank you for the tips.

I'm glad to hear that, well done! Were there any significant additional costs incurred?

Yes, there will indeed be additional costs because the heating contractor exceeds his portion within the general contractor’s scope. So, the extra materials (pipe meters, motors, etc.) will have to be charged to us.
At least the heating circuit valve was replaced free of charge by the general contractor.

But the extra cost is worth it to me.