Design of underfloor heating for KFW 55 house with ventilation system

We go through everything there again. Downstairs there is definitely still some leeway with the pipe lengths and we could get by in most rooms without additional heating circuits. Upstairs it actually gets tight aiming for the 100 m.

I predict that this will exactly become the problem. Downstairs, in my opinion, it will always get warm. Just the ground floor with TV, cooking, baking, and regular presence of people heats up "by itself."

With this standard 0815 design, you will definitely get a bathroom that is too cold. For example, I have 3 heating circuits there and it is still too cold – especially if you already have an undercoverage at a 35°C design temperature. This is what our planning looked like:

The general contractor does not care; it is not a warranty case. The place gets warm. However, then you have to turn up the heating curve so that the bathroom or other critical rooms get warm. The consequence is that you have to "choke" the other heating circuits so that the living room does not reach 25°C. Then such a heat pump runs like a sack of nuts. You will not fix that even with a new/modern heat pump in 15-20 years. That is a problem forever.

Therefore, it is worth the effort now to discuss it down to the last detail.

That is why it is now worth the effort to discuss it thoroughly.

If your counterpart even goes along with it. More likely with individual trades than a general contractor. But you are certainly right, in my opinion the topic is too often given too little attention during planning, which cannot be significantly changed afterward, and that’s why I don’t understand why, for example, a general contractor can be so "unconcerned" about it.
You don’t want anything handed to you for free, just want to be sure to have achieved the optimum in efficiency and cost-effectiveness. Having to dig around to get any information at all is really annoying…

Hello, the first mistake is already in the contract design with the general contractor. If it is not exactly defined here what services the heating trade owes, you have a poor negotiating position after signing. I still wish everyone much success in negotiations. Maybe you can get the heating technician journeyman on your side in time and negotiate something directly. The journeyman did that with me. He put aside the calculation from the manufacturer and implemented my calculation. The master did not notice that; he was no longer on site after the first planning inspection. Regards

Hello everyone,

I wanted to share the current status as the OP.

We have prevailed and had the HKV on the upper floor replaced with a larger one, so now we have the possibility to install 2 HK in all the rooms upstairs.

I thank you for the tips.

I'm glad, well done! Have any relevant additional costs arisen?

Yes, so there will actually be additional costs because the heating technician exceeds his amount with the general contractor. So the additional material (pipe meters, motors, etc.) must then be charged to us. At least the HKV was replaced free of charge by the general contractor. But the additional cost is worth it to me.