Mould in the corner of newish double glazed window and on wall?

The problem is due to humidity/water vapour that you put into the house by breathing and general living and your handling of the heating system.

Every time you turn the heating down or off, you unbalance the humidity/heat relationship.

For every temperature there is a specific amount of water vapour that is held in suspension.

You describe the effects of condensation.

Each time the temperature drops, its ability to hold water vapour diminishes - that water has to go somewhere, usually it will condense onto the nearest cold surface, a window. In your case its an already damp cold wall.

To quickly solve your problem, you need to buy and keep on a de-humidifier. Leave it on 24 hours a day remembering to empty the tank.

Within a few weeks the problem will go away.

Perry525
February 2008