A misted window is immediately noticeable. More useful is what happens before and afterwards: how the room is used, what ventilation is present and whether the humid air can escape.
Airing is an addition
Flemish guidance distinguishes between temporarily airing a room and ongoing ventilation. Briefly opening a window can help, but does not replace normal air renewal. Check grilles, extraction points and the operation of any existing ventilation system too. Flanders: airing and ventilation.
Make the pattern visible
For a few days, note when you see condensation. This does not need to be a complicated investigation: a short note for each room often provides a useful starting point for an assessment.
- Which windows or surfaces become damp?
- Does it return after sleeping, showering, cooking or drying laundry?
- Are grilles open and visible extraction points unobstructed?
- Which ventilation system setting is being used?
Discuss how the room is used
Include any recent changes, such as new windows or a different layout, in the discussion. Ask which air supply and extraction will be assessed, what maintenance is needed and how to use a proposed solution every day. If one area remains particularly wet, also have another possible moisture source investigated.
