Trimming glazing bead seals to reduce air leaks

[seanblee]

I recently bought myself a thermal imaging camera, which I've started using to try and find issues with cold bridging and inadequate insulation. I've already fixed one issue with the back door cams missing their receivers so not pulling the door onto its seals properly, but I've found another issue with almost all of my (2007) double glazed windows - they leak air from the seals on the beads at the corners. My newer windows have beads that are mitred at the corners, so the seals meet neatly, but it looks like the shorter beads here are scribed around the longer beads and the longer seal is holding the shorter one away from the glass. Any thoughts on the best way to trim them to resolve this, please? Thanks!

[Russell griffiths]

Take all the beads out and do a re test. 

I bet this draft is coming around the glass unit and the bead is pushing it to the corner gap. 

You could remove a bead and seal the unit into the frame using  illbruck airtight foam, then re install the beads. 

 

I would remove one or two beads carefully, to make sure the glass is secure on packers and that it stays in place. 

[seanblee]

11 minutes ago, Russell griffiths said:

I bet this draft is coming around the glass unit and the bead is pushing it to the corner gap. 

You could remove a bead and seal the unit into the frame using  illbruck airtight foam, then re install the beads.

Thanks, I'll take a look. My only concern with foam would be blocking drainage holes in the profile - I'm assuming there would be some to drain any water that got past the external frame-to-glass seals? I saw another thread where someone wedged foam backer rod between the glazing unit and frame, perhaps that's a safer option?

[Russell griffiths]

Yep backer rod would work, maybe a dab of silicone on the corners as when you fold it around it will naturally have a bit of a gap, or mitre them ???

[seanblee]

Given the state of the rest of the installation, I was unsurprised to find the glazed unit wasn't packed in correctly on my test window - it was sitting on a couple of packers at the bottom but otherwise free to move. I've packed it on all four sides and inserted some backer rod around the unit, so I'll see what happens - only another 16 units to sort if it's successful...!