ᐅ Proper Ventilation and Dehumidification

Our construction started in autumn and has progressed well. The screed is in place, and both interior and exterior plastering are finished. Since yesterday, the screed has been heated using a portable heater connected to the underfloor heating system. As a result, the humidity inside the house is quite high. The windows are fogged up, and all external corners are damp. We have received various suggestions on how to properly handle the moisture issue.

- Construction company: "Dehumidifiers/building dryers are not necessary, just air out three times a day with full window opening, no permanently tilted windows."
- Painter: "Simply leave one window tilted open on each floor during the day for good cross-ventilation."
- Plumbing/heating company: "In winter, ventilate fully no more than twice a day and maybe use air dehumidifiers."
- Engineer friend: "Use heaters and two high-end building dryers, and tilt some windows."

Currently, we do the following: Depending on our work schedule, we ventilate fully two to three times a day. We have placed an air dehumidifier on each floor (basement, ground floor, upper floor), each rated by the manufacturer for rooms up to 72m² (780 sq ft), and run these dehumidifiers during the day. At night, we turn them off partly to save on electricity costs and partly because we prefer not to leave the devices running unattended for 12 hours. These devices can also be used later for improving indoor air quality and drying laundry.

Do you have any recommendations or corrections?

Instead of using a dehumidifier, use a construction dryer. You can rent one for 14 days and run it 24 hours a day. The electricity costs are irrelevant since it’s necessary and should be factored into the additional construction costs.

Dehumidifiers don’t really do much other than remove moisture from the air. Construction dryers actually draw moisture out of the walls.

By the way, one per floor is enough 😉

Avoid tilt ventilation; it’s better to use rapid airing (opening windows fully for a short time).

Ok, great, thanks. We will speak with the construction company again to see if they can provide something. That would probably be better 🙂

You can borrow them from a hardware store.
If the construction company has something like that, great, but why should they?!

The only real mistake you can make is tilting the windows – that says a lot about the painter and the "engineer." Using a drying dehumidifier or quickly airing out the room by fully opening the windows, depending on how much time you have, both are fine.

Thanks a lot for the feedback, that really helps!