Recently we had to have a double glazed unit in our porch removed to allow a settee in through the window into the house. Since the double glazed unit has been replaced there seems to be some corrosion in between the glass on the aluminium, why? and will this cause a problem with the unit?

Susan, Edinburgh, December 2013

Sounds as if unit has Brocken down. Look for misting or water between glass, if so you need a new unit.

Len, December 2013