One of the panes in my double glazing has gone misty and has condensation on the glass inside the unit. How has this happened and can it be repaired?
A. It cannot be repaired but must be replaced. If your windows are still under guarantee contact the installation company to come and replace it. If not, your local glass shop will probably be your cheapest and best option for a replacement. The sealed units used in double glazing are manufactured using two sheets of glass with an inset spacer bar between them. The spacer bar has tiny holes (only on the surface that is facing towards the inside of the sealed unit) and is filled with a desiccant material that absorbs moisture. The spacer bar should first be sealed on both sides against the glass and then the perimeter of the unit is filled and sealed with a liquid butyl or poly-sulphide compound which quickly sets to a rubber like consistency. You now have a ‘hermetically sealed unit,’ i.e., the air is trapped inside forming its own ‘mini-atmosphere.’ As the outside temperature reduces, water vapour in the air trapped within the unit tries to condense on the cold inner surface of the ou
