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The Truth About Condensation

Double Glazing Condensation | Window and Door Repairs | PVC Windows Carlisle

What causes external condensation on double and triple glazed windows and doors?

People are oftens surprised and worried to see external condensation on double or triple glazing, and the common misconception is that the sealed unit is faulty. Condensation on the outside of windows can be particularly noticeable during the cooler seasons - Autumn and Winter. External condensation is actually a sign that the window is working - incredibly well!

Many customers may be a little bit concerned at this natural phenomenon, however, what it's actually demonstrating is how well the window/door is keeping the heat inside your house. As the cold atmosphere to the outside hits the lovely warm double/triple glazed unit, the moisture beads become visible and the external face of the outer pane of glass will mist up. This is happening because of a low emissivity coating on the internal pane of glass, which is there to reduce heat loss through the sealed unit.

"But what if I have double glazing and the condensation is on the inside of my house?"

This could be happening for a couple of reasons. The most likely is that the double glazing is older than the modern equivalents and hasn't got the same thermal characteristics of it's modern counterparts. Nowadays, most sealed glazing units are argon gas filled and have a thermal coating (Low E, Ultra N, Planitherm to name a few). The sensible manufacturers and installers even use a 'warm edge spacer bar' which is a thermally coated spacer that creates the cavity between the two/three panes of glass.

If your windows are around ten years old or younger, it is likely that something else could be causing the problem - one common issue we come across is the unit has been installed back to front! Make sure the installers you use are competent and experienced in PVC windows and doors.

"Help! I've got condensation inside the panes of glass!"

This is a sign of the glazing unit no longer working. It has 'failed', to put it bluntly. Customers often refer to this as it's 'blown' or 'misted up'.

The reason for the condensation in this situation is that the dessicant beads (a bit like silica beads you find in new trainers!) inside the spacer bar are saturated and no longer drawing the excess moisture and heat from the cavity between the panes of glass. There are people who claim they can 'fix' failed double glazing, however, if we're brutally honest with you (as we always are), this is pretty much just wasting your time.

For the time and effort involved in splitting the units, deconstructing the spacer bars and then renewing the dessicant and outer seals, you will have racked up the same, if not greater, costs than just simply replacing it with new double glazed units. Once a unit has been split and resealed not by a seasoned professional, the unit is likely to never be the same again.

If you have any other questions or queries about condensation or windows and doors in general, give our experts a call on 01228 599777 or drop us an e-mail

Posted by: / 12 October 2016 at 09:23