Velux Clearances

[Moosewain]

Hello. New to this forum so please bear with me.

I have read through some past threads but can't find an answer to my question. I have 2 new GGL Velux windows to fit. Just had a confusing hour or so with the installation manual and am none the wiser as to the function of the insulation collar (code BDX). Is this a mandatory item as none of the merchants I have visited supply this part. If it is not mandatory do I reduce the size of the trimmed opening to the frame size only? Of course if it is mandatory, I will have to go shopping again!

Thanks in advance.

 

[^woody^]

The BDX seems to be some sort of flashing collar and not insulation?

Either way it seems optional as the roof felt is dressed up to the velux with strips of felt/membrane (ie similar to the BDX function) and then the standard flashing kit is installed above this prior to tiling

 

[Alastairreid]

//www.diynot.com/forums/viewtopic.php?t=71012

 

[Moosewain]

Thanks a lot for the help. It would seem that the little shopping trolley in the instruction manual is therefore code for "optional". cryptography at it's best! I will reduce the size of the suggested opening to take just the window frame, allowing enough "play" for the flashing kit.