Condensation forms when humid indoor air meets a surface below its dew point. In Dubai that is usually single-glazed or metal-framed windows chilled by the AC, or any window on a humid morning. Persistent condensation means indoor humidity is too high (above ~60%) and it points to where mold will appear next — the timber or gypsum reveal, the sealant, and the sill.
Key takeaways
- Interior condensation = indoor humidity too high for the coldest surface.
- Metal frames and single glazing are the usual cold bridge.
- The reveal, sill and sealant around the window grow mold first.
- Fix the humidity; wiping the glass is only damage control.
Why condensation forms on your windows
Air can only hold so much water vapour at a given temperature. Cool it and the excess condenses out onto the nearest cold surface. Glass — especially single glazing — and aluminium frames conduct heat well, so with the AC running they sit several degrees below room temperature. Add high indoor humidity (cooking, showers, drying laundry, many occupants, humid outside air coming in) and the glass drips.
Where the mold goes
Not usually on the glass itself, but on the porous materials around it that stay wet: the plaster or gypsum reveal, a timber sub-frame, the paint on the sill, and the silicone seal. You will see black speckling in the corners of the reveal and dark lines in the sealant.
Reducing condensation
- Get indoor humidity below 60% — measure it, improve extraction, run the AC longer at a moderate setpoint. See the right humidity level.
- Improve air movement past the windows — do not block them with heavy curtains that trap cold, damp air against the glass.
- Wipe and dry sills and reveals in the morning until the humidity is under control.
- Avoid drying laundry indoors without ventilation.
Frames and glazing
If a window condenses badly every day despite reasonable humidity, the frame is a strong cold bridge. Thermally-broken frames and double glazing greatly reduce it. Between the glass panes of a sealed unit, condensation means the seal has failed and the unit needs replacing.
Heavy curtains drawn tight against a cold window trap a pocket of cold, humid air — the reveal behind them is a classic hidden mold spot. Leave a gap for air to move.