A misted window is a clue. Start there.

Make a small room record

Note the room, the time and the weather. Take a dated photograph of the affected area and record whether the mark changes after rain, cooking, bathing or clothes drying. Keep the record factual; the location of a damp patch alone does not establish its cause.

Know how the air is meant to move

Find the extractor fans, background vents and any whole home ventilation controls. Read the instructions before adjusting them. Do not block intended ventilation. A fan that is broken, unusually noisy or ineffective needs attention.

Ask whether a kitchen hood extracts outside or recirculates. Those arrangements do different jobs, so the presence of a hood is not enough to tell you how moisture leaves the room.

Look beyond the window

Leaks, building defects, cold surfaces and insufficient ventilation can all need investigation. Ventilation and heating also need to be considered together. There is no universal window opening routine that fixes every building.

Know when to pass it on

Report persistent damp or mould to your landlord or a suitable building professional with your photographs and dates. Ask for the underlying cause to be assessed. Repeatedly wiping or painting an affected surface is not a substitute for resolving the problem.

This is a guide to observing and reporting a home issue. If you are concerned about symptoms, seek advice from an appropriate health professional.