Screed in summer - Functional heating

Here is my brief experience report. Maybe you can also share your experiences with functional heating? Duration, temperature, power consumption, ...

Our cement screed was laid at the beginning of July. Exactly one week ago, the heating was started – 2 weeks later than planned because the customer service for commissioning the heat pump had no earlier appointments due to the holiday season. Not so bad, I think.

For us, there was absolutely no dripping from the walls/windows immediately after laying the screed. The humidity was sometimes at 80%, it was muggy and hot (outside temperature over 30⁰C), but you could not see the moisture. Do you have an explanation for that? We plastered the whole house with pure lime plaster, all walls made of Poroton bricks. Could this contribute to better moisture regulation? Even with these amounts of water? My two neighbors (Ytong and prefab house with gypsum plaster each) had water running down from the windows. They sometimes had to vacuum the water off the panes with Kärcher window vacuum cleaners every time they ventilated...

On the topic of functional heating: Yesterday, the underfloor heating reached 40⁰. Room temperature 34⁰C!!! Humidity before ventilation 54%, after ventilation 58%!!! I think I can slowly save myself the ventilation ;). It doesn’t make sense during the day after all. Today I was ventilating at 5 a.m. (!) I managed to lower the indoor temperature from 34.9⁰C to 27⁰C. Unfortunately, with the current weather, it does not work during the day. Power consumption in the first 7 days – 110 kWh, half of which was covered by the already connected photovoltaic system. The air-water heat pump cycles very often and runs with max 2200W (today from 5 a.m. until now without interruption). I’m curious about week 2.

Our functional heating started last week. Our windows are tilted open all the time, according to our general contractor, this is no problem during the summer at these temperatures. Water on the windows only occurs with a high temperature difference between inside and outside (so rather in winter).

1. Humidity condenses depending on the level of humidity at cool spots. You see mold on exterior walls of old buildings in winter. In summer, you have the problem that there simply are no cool surfaces. It's basic physics and not to be attributed to any miracle stones ;-)
2. Why 40 degrees with the underfloor heating? How is the heating system designed? I think you do it that way because it is specified by the heating installer/screed layer.
3. Cycling of the heat pump. That must not happen at all. There should be a special screed program for this, so that no cycling occurs.

1. Humidity condenses depending on the level of humidity on cool surfaces. You see mold on exterior walls of old buildings in winter. In summer, you have the problem that there are simply no cool surfaces. It's simple physics and not to be attributed to any miracle stones ;-) 2. Why 40 degrees with underfloor heating? How is the heating designed? I think you do it that way because it is specified by the heating installer/screed layer. 3. Cycling of the heat pump. That should not happen at all. There should be a special screed program to prevent cycling.

Thank you for your feedback. 1. Yes, I understand. "Beer-from-the-fridge principle." I just wonder why it did not condense at all, even during the cooler days at the end of July. 2. Yes, the screed layer specified that, so it is done that way (because of the warranty). 3. The cycling of the pump annoys me as well. The heating installer chose a screed heating program. He also said from the beginning that the pump would cycle. Here in this picture (app of the photovoltaic system) it is clearly visible.

Cooler means 20 degrees outside temperature and above. You have a well-insulated house, which then certainly still has the corresponding temperatures on the inside of the walls and the dew point is not undercut.

We heated in June. But with gas. We also had very little condensation. However, the air was noticeably humid. We did heat to a higher temperature, and it was incredibly warm in the house. Just muggy warm air. However, I still can't remember any water on the windows.