Screed drying and humidity

Hello,

about 6 weeks ago the screed (anhydrite screed) was laid at our place and the screed heating program has been running at 45 degrees for 1 week. Before the screed was heated, we always had about 70% humidity before ventilating (the rooms were naturally cold), after ventilating hardly below 60%. Since the heating has been running, we have a room temperature of 27 degrees and a humidity of 24-30%. Why is the humidity so low now? I think there should be liters of water in the house because of the new building and the screed, and the air should still be very humid? Is it so dry because no one lives in the house yet or because it is so warm in the house? How was it for you?

Best regards
Sabine

A look at the Mollier diagram helps: assuming you had 18 degrees and about 60% humidity, then there were approximately 7g/kg of water in the house. At 27 degrees and 30% humidity, it is also about 7g/kg. Conclusion: the absolute humidity is roughly the same, even tending to be a bit drier, which is clear when you heat and ventilate. The water in the building does not flow out of the walls and floors in streams; it is a very slow process.

Thank you for the explanation, I had already read that it would get so humid in the house during the screed drying process that water would run down the window panes, and that is not the case with us, which is why I was surprised. So with falling temperature, it will also get more humid inside the house again, this morning it was only 24%.

Best regards
Sabine

The first seven days with cement screed produce water on water. To prevent it from cupping or cracking, the screed layers leave the house with completely closed windows and doors, also warning you not to change anything for seven days. Do not enter, do not ventilate, do nothing. When you open the house afterward, it is like a steam bath inside. It is hot and completely humid. The fresh cement released enormous heat and water during setting. But now open the shutters and let air in, otherwise the plaster will fall off the walls.