Triple glazed window - sound insulation

[Jupiter01]

It looks to me like the rubber meets well at the top? Perhaps it also meets well at the bottom, but that is out of shot.. But it looks like the opening window frame has bowed away from the part it's supposed to meet with in the middle

Exactly right. This is the issue.

Here are some more pictures, as requested.

From the inside, the bowing can be seen too (along with the air dust) in the middle section of the window.

Please let me know if you require any additional images.

I will await further advice. Thanks again.

 

[Notch7]

Your top hung windows might not compress the seal around the middle- clips that pull in can be fitted if that's true

 

[crank39]

This always a problem with oversize casements, they look like 1200mm to me and in my experience anything over 1000mm you run the risk

 

[robinbanks]

To what extent are you willing to go to resolve this?

Fitting something like crescent locks (the ones you see on sash windows that rotate and tighten up as they turn) would be a quick-to-fit albeit visible solution to pulling the sides in

Removing the opening light, routering a hole in the bottom of the frame and installing a reinforcing bar that bends the frame slightly inwards in the centre would take a lot longer but be an invisible solution

 

[Jupiter01]

clips that pull in can be fitted if that's true

Which type of clip should I use in this instance? Thanks

 

[Jupiter01]

To what extent are you willing to go to resolve this?

Fitting something like crescent locks (the ones you see on sash windows that rotate and tighten up as they turn) would be a quick-to-fit albeit visible solution to pulling the sides in

Removing the opening light, routering a hole in the bottom of the frame and installing a reinforcing bar that bends the frame slightly inwards in the centre would take a lot longer but be an invisible solution

I would definitely prefer an invisible solution please.
I need to solve this as it's letting the cold and noise through.
Couple of thoughts based on what I have understood here:
1. Can I use some sort of catch in the middle section which comes into play when the window is closed?
2. Can I use thicker rubber seal in the middle section to close the gap?

 

[Notch7]

Which type of clip should I use in this instance? Thanks

this sort of thing

White Upvc Window Sash Cavity Closing Wedge Draught Sealing 5 X Pairs

This is a white Upvc Window Sash Cavity Closing Wedge Draught Sealing pack of 5 pairs. Pulls the sash and outer frame parts together on the hinge side of opening out windows and help prevent them bowing and creating draughts.

upvcspares4repairs.co.uk

 

[crank39]

The closing wedges are only effective in between the hinges so in this case along the top of the casement but that isn't where the gaps are, now if it was a side hung casement then you'd fit them on the side and they would pull the gap in

 

[robinbanks]

I would definitely prefer an invisible solution please.
I need to solve this as it's letting the cold and noise through.
Couple of thoughts based on what I have understood here:
1. Can I use some sort of catch in the middle section which comes into play when the window is closed?
2. Can I use thicker rubber seal in the middle section to close the gap?

For the invisible solution you really need to mount something inside the frame of the window. As you have it there the opening light is bent, or the frame it closes against is bent. It's quite typical for PVC to suffer this; it's plastic and doesn't have a great deal of structural integrity over long lengths. All it needs to do is bow by a few millimeters in the middle and the sealing gaskets won't meet the frame any more. Quite expected for a long opener secured top and bottom, to bow at the sides. It's possible to get reinforced profile, where there is a metal box section inside the PVC from factory. If you're DIY competent you could fit something after market to achieve the same. Suffice to say, it would be along the lines of finding a metal bar suitable to mount inside the frame, drilling a hole in the bottom so the bar could be inserted, bending the opener so its bulge matches the curve of the frame it seals against, and then securing the metal bar. Not impossible, but not a job for a DIY novice

For the visible solution, look up crescent locks or sash locks:

There is a ramped section that can be arranged to pull the frame and opener together where they currently bow apart (this is your query #1)

2. Can I use thicker rubber seal in the middle section to close the gap?

You can try, but then you have something pushing the frame and opener apart in the same way the existing seal has and over the time it'll likely just bend the opener more, bringing you back to where you are now, with an even more bowed frame