Condensation or dirt? Locate the moisture first

The position matters more than the label

A cloudy-looking window is not automatically a dirty window. The first useful distinction is where the moisture or haze appears: on the room-side surface, on the weather-side surface or apparently within the glazing unit. If you cannot tell, keep that uncertainty in your description. A cleaning enquiry can begin with “the bedroom window looks misty in the morning” without you having to decide the technical cause.

Pilkington's explanation of window condensation distinguishes inside, outside and between-pane condensation. It associates persistent condensation between panes with an insulating-glass-unit seal problem. That does not mean a distant photograph provides a diagnosis. It means the location changes which question needs answering, and ordinary cleaning of accessible surfaces cannot promise to fix a problem inside the sealed unit.

Write a small observation record

You do not need to monitor the window continuously. Note the room, the pane, approximately when you notice the effect and whether it later disappears. If the room-side surface is within normal safe reach, you may already know from everyday use whether it is wet. Do not lean out of the window, climb or dismantle anything to establish the outside condition. Use observations you can make without creating a new task or hazard.

Keep cleaning and building questions separate

Internal cleaning may still be useful where fingerprints, everyday marks or other surface dirt need attention. State that request independently of the moisture concern. “Please clean the inside windows; one bedroom pane also appears misty within the unit” is a clearer brief than “please clean away the condensation problem”. The internal cleaning page describes the relevant service route.

If your question concerns recurring room-side moisture, use the window manufacturer's guidance and appropriate building advice rather than assuming more frequent cleaning resolves it. Do not block vents or alter a ventilation arrangement as an experiment prompted by a cleaning article. The cause and suitable response can depend on the room and building; a cleaning visit is not a substitute for that assessment.

Use a hypothetical comparison

Consider two households looking at apparently similar hazy panes. In the first home, the visible effect changes during the day and the homeowner can identify moisture on a surface. In the second, a patch appears persistently within a sealed unit and cannot be reached from either side. The useful next enquiries differ, even if both owners initially call the problem “dirty double glazing”. Neither household needs a promise that a stronger glass-cleaning product will solve it.

When asking the installer or a glazing specialist for help, retain any product details, installation information or warranty documents you already have. There is no need to search inaccessible labels or dismantle the frame. An ordinary room photograph and a description of the pattern may be enough to start the conversation; the specialist can explain what further information is needed.

Choose a service without mixing the expectations

For routine dirt on the inside face, use the internal collection. For external dirt, use the relevant exterior window-cleaning route. If both faces are wanted, make that explicit using the inside and outside service information. The four-clean minimum for a regular external arrangement does not turn an internal or repair enquiry into a recurring commitment.

Most importantly, record what you can actually observe. Locating the effect, identifying when it happens and preserving uncertainty where necessary gives both the cleaner and any glazing specialist a clearer starting point than treating every cloudy appearance as the same cleaning problem.

Choose your next step

View internal window cleaning options