Forgive my ignorance - but our flat was only built last year and yet we have condensation inside all the double glazing windows and patio doors. Is this normal? The water is beginning to cause mould on the window panes. Or does this mean something wasn't installed right? I have a 2 year new house build code time, but don't know if this is something I should expect the builders to sort out.

Jill "I wish I knew something about DIY" Webster, December 2009

ventilation is the key here, you say its a new build? these places are insulated very well sometimes a bit too much, you need some draughts to circulate air, double glazing insnt meant to be airtight, it could also be the concrete in the building sweating as it settles! if you dont give it air it will continue for ages!

carl, August 2010

Unless of course the condensation and mould growth is Between the panes - in which case - you have a case.

Continuing good luck...

Peccavi, December 2009

It's curtains for you...

There's very probably nothing wrong at all with your double glazing.

In the winter we run our houses warmer - warm air can carry more moisture than cold air - when the warm air meets a cold surface it cools and water is squeezed out - condensation,

Your solutions are:
Wipe up the damp as soon as you see it - stops mould growth
Insulate the windows with curtains or blinds to form a barrier if you can
Ventilate the house a little more
Reduce the heating if you can - even a bit - save money
Keep bathroom and kitchen windows open when creating steam - even in the coldest weather just a bit open - and keep the doors closed.
Consider a dehumidifier - mine cost £160 and can easily suck a litre of water from the air in a day!

What you describe is a modern curse brought about by the combination of Central Heating, Double Glazing and no natural ventilation - older houses tend to suffer less because they're more draughty.

Do a test - boil a kettle near a closed window when it's cold outside - see what happens. The do it again with the window open a bit.

Good luck...

Peccavi, December 2009