ᐅ Screed Installation in Summer – Functional Heating

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

Our cement screed was installed at the beginning of July. Exactly one week ago, the heating phase started – two weeks later than planned, because the customer service for commissioning the heat pump had no earlier appointments due to the holiday period. Not a big deal, in my opinion.

In our case, there was absolutely no dripping from the walls or windows immediately after laying the screed. The humidity was sometimes around 80%, it was muggy and hot (outside temperature over 30°C (86°F)), but you couldn’t see the moisture. Do you have an explanation for this? We plastered the whole house with pure lime plaster, and all walls are made of Poroton bricks. Could this contribute to better moisture regulation? Even with these amounts of water?
Both of my neighbors (one with Ytong blocks and the other a prefabricated house, each with gypsum plaster) had water running down their windows. They sometimes had to use Kärcher window vacuum cleaners to remove the water from the glass after every ventilation.

Regarding functional heating:
Yesterday, the underfloor heating reached 40°C (104°F). Room temperature 34°C (93°F)!!! Humidity before airing was 54%, after airing 58%!!! I think I can gradually skip airing 😉 . During the day, it doesn’t seem worthwhile. Today, I aired at 5 a.m. (!) and managed to lower the indoor temperature from 34.9°C (95°F) to 27°C (81°F). Unfortunately, with the current weather, airing during the day doesn’t work. Electricity consumption in the first seven days was 110 kWh, half of which was covered by the already connected photovoltaic system. The air-to-water heat pump cycles frequently and runs at a max of 2200 W (since 5 a.m. today without pause).
I’m curious about week two.

Last week, we started functional heating. Our windows are tilted open all the time, which our general contractor says is not a problem during the summer temperatures.
You only notice condensation on the windows when there is a large temperature difference between inside and outside (so rather in winter).

1. Humidity condenses depending on the level of moisture in the air at cool surfaces. You can see mold on the exterior walls of old buildings in winter. In summer, the problem is that there are simply no cool surfaces. This is basic physics and not due to any kind of miracle solution ;-)

2. Why 40 degrees Celsius (104°F) for the underfloor heating? How is the heating system designed? I assume you are doing this because it was specified by the heating engineer or screed installer.

3. Short cycling of the heat pump should not occur at all. There should be a specific screed program to prevent short cycling.

KarstenausNRW schrieb:

1. Humidity condenses depending on the level of humidity at cool surfaces. You see mold on the exterior walls of old buildings in winter. In summer, the problem is that there simply are no cool surfaces. This is basic physics, not due to any miracle products ;-)
2. Why 40 degrees Celsius (104°F) for the underfloor heating? How is the heating system designed? I guess you’re doing it because the heating installer or screed contractor specified it that way.
3. Cycling of the heat pump. That should not happen at all. There should be a special screed heating program to prevent cycling.

Thanks for your feedback.
1. Yes, I understand. The “beer-from-the-fridge principle.” I’m just wondering why there was no condensation at all, even during the cooler days at the end of July.
2. Yes, the screed contractor specified it, so it’s done that way (for warranty reasons).
3. The cycling of the pump annoys me as well. The heating installer selected a screed heating program. He also said from the start that the pump will cycle.
You can clearly see it here in the picture (app of the photovoltaic system).

Cooler means an outside temperature of 20°C (68°F) or higher. You have a well-insulated house, so the corresponding temperatures on the inside of the walls will certainly still be maintained, and the dew point will not be undershot.

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