Double glazing oddity

[Simpo Two]

Just taken delivery of a new d/g window unit, and was told that the cill is not fixed to the frame - apparently I just put it in the bottom of the aperture, then sit the window unit on top. I was expecting some kind of snap-fit arrangement.

It just seemd odd that whilst the glass is super-dooper low-emission K-wotist, there's no need to fix the unit to the cill! How can that be thermally efficient?

[V12Les]

The cill should sit below the height of the inner cill so dosen't require any u value. You can also fit the cill prior to fitting the frame but make sure you run a thin bead of silicone along the rear of the cill where the frame will sit and return the bead at both edges. The cill also needs to be screwed to the frame.

Edited by V12Les on Friday 4th December 18:34

[darronwall]

dont screw the cill to the frame,just silicone it together,if its a wide window and you feel you need to,fix it up through the cill towards the rear of the cill

[Simpo Two]

Thanks folks, it's only 1200mm wide so I'll just sit them together with a sealant bead.