Failed double glazing Velux unit

[dannat]

Hello Fellow DIYers,

I've recently noticed that condensation is building up on the inside of my Velux double glazing unit in my loft conversion. I'm aware that the unit has failed and probably needs replacing.

Does anyone have any experiences of how easy it is to replace the unit of a velux window (it can tilt 180degrees so is easily accessible - ie no roof access necessary)?

Roughly how much does it cost to replace a unit approx 740mm X 600mm?

Finally how do I go about accurately measuring the unit in situ (it obviously recesses into the frame slightly and I don't want to remove it until I have a new unit to replace it with) and what allowances should there be?

Many thanks in advance,

D

[eddiecleaner]

We replace the pane of glass (i.e. both panes as they are double glazed and sealed) in East Anglia and charge around £100. It takes about 1 hour. :)