Condensation on inside of double glazing

Hi - I had some bedroom windows replaced a few months ago.
In the mornings, there is condensation from the bottom, pretty much half way up the windows.
What could be the cause?
A defect in the installation?
It is still under warranty, so can get them back.

Or could it be something else?
Its not an overly-warm house, but liveable.
Heating is on in the evenings until about 9pm and then on again about 5am for a couple of hours. There is a radiator under the windowsill.
Loft above the bedroom recently insulated with 8 inches of roll insulation.
There is an adjustable wall vent with about 8 slots - I have moved the slider to expose about a third of the vents. It is on teh same wall as the window.
I keep the bedroom door shut over night because the hallway is cooler than the bedrooms, as there are no ratiators out there.

Any thoughts?
Cheers!

same here, we have vents on the windows themselves, which are suppose to be kept open at all times. if they are not kept open we have the same condensation as you described...

This a fairly common problem when old windows are replaced.

All sorts of normal activities cause moisture to be released into the air. Cooking, drying laundry, showering and bathing, ironing, breathing...

The warmer the air in the house the more moisture the air can hold.

The glazing, while argon filled etc etc... will experience a certain amount of thermal bridging which means the glass, especially around the edges, will be the coldest thing in the room.

The draughty... or at least well ventilated... windows you've had taken out have been replaced by sealed, airtight units. This simply doesn't allow for the moist air to be carried out naturally.

The only way to stop the condensation is to keep the trickle vents or other vents open. If trickle vents are not fitted go back to your supplier and enquire as to whether they can be retro fitted. You could argue that they should have advised you to have vents from the outset but you will probably end up having to pay for them.

If they cannot be fitted you may have to keep the windows open a crack overnight, find dessicant crystals or continue mopping up each morning.


Good luck...