Misting on your windows is usually caused by condensation, and where it appears tells you almost everything I need to know about what’s causing it. It can form on the inside of the glass, on the outside, or between the panes, and each one has a different cause and a different solution.
Inside condensation is the most common type, and in most cases the window itself isn’t the problem. Everyday activities such as cooking, showering, boiling the kettle, even just breathing, release a surprising amount of moisture into the air. When that warm, damp air meets a cold surface like glass, condensation forms.
This tends to be worst in winter, when homes are kept warm and windows stay closed for longer. Modern homes are also significantly more airtight than older properties, which is great for energy efficiency but can trap moisture indoors if ventilation isn’t adequate.
This type of condensation is usually manageable. Opening windows regularly, running extractor fans in kitchens and bathrooms, and avoiding drying washing indoors all help bring humidity levels down. If the condensation wipes away easily and only appears occasionally, your glazing is likely in good working order.
I find that condensation on the outside of windows tends to cause unnecessary alarm, although in reality it’s often a sign that your double glazing is doing its job well. Energy efficient double glazed units are designed to retain heat inside the property, which means the outer pane stays relatively cool overnight. When the temperature drops and humid outdoor air comes into contact with that cool surface, condensation forms on the exterior glass.
External condensation normally clears once the sun comes up or temperatures rise. It doesn’t indicate a fault, and homes with high-performing glazing are often the ones most likely to experience it.
Moisture trapped between the two panes of glass is a different matter. This happens when the sealed unit has failed, and unlike the other types, it can’t be wiped away from either side.
It tends to develop gradually, starting with a faint haze at first and becoming more persistent over time. You may also notice the window doesn’t feel as warm as it used to, or that there’s more of a draught near the glass than there used to be.
If you’re seeing this, it’s a sign the sealed unit has failed and needs replacing rather than something ventilation can fix. I’ve covered what causes this and how I go about fixing it on my Sealed Unit Replacements page, if you’d like more detail.
The good news is that this normally only affects the glass unit, and not the whole window. In most cases, your existing frame can stay exactly where it is and just the sealed double glazed unit needs replacing, which is a much smaller job than a full window replacement.
Call me and i will come and give you a free quote to get them replaced.