Duplex Spacerbars - Georgian style Windows

4 Nov 2019
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United Kingdom
Hi All,

I recently replaced the glazing in my house, with Georgian effect panes which are made with horizonal and vertical duplex glazing bars, to give the Georgian small pane effect. The problem I am faced with is that the horizonal and vertical spacer bars make up the smaller panes, are a few millimetres smaller than the glazing par which surrounds and seals the window, therefore there is a small gap at each side of the spacer bars. When I push on the centre of the window pane, the spacer bar inside the window moves, hitting off both panes, causing a rattling sound.

I spoke to the glazing company who advised as their manufacturer has made the panes in this way, based on the dimensions of the frame, so it must be right. I feel like the glazing company is not moving on their stance regarding the windows.

Can anyone please give advice if they have experience of this, is this known to be the way spacer bars are made within Georgian effect panes or how I can have this resolved? The older panes which were replaced did not move...

Thanks in advance....
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duplex bars are deliberately thinner than the air gap -as far as I know it is to avoid thermal bridging.
Only the outer most bars i.e both sides, top and bottom are the correct width to give you the correct cavity, everything inside of that i.e the duplex bars are 2mm thinner, maybe Ronnie our resident double glazed unit manufacturer can elaborate but I think it's do with expansion of the bars causing the glass to break, your glass man isn't pulling your leg, think it's industry standard but I don't mind being corrected
Many thanks for the quick replies. Should there be some sort of anti-rattle system to limit the spacer bars from moving within the glazing?

All new to me, but I'm hoping this is standard to avoid confrontation...
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Notch7 is spot on, the duplex bar is normally 2mm thinner than the outer ' spacer bars ' to eliminate thermal bridging. As Crank says it is an industry thing, so completely normal. Must admit don't normally hear too much ' rattling' of duplex bars, but if doors or windows are closed 'hard' then they will rattle , never had a need for any ' anti rattle' before , unlike Georgian bar inserts!
I've noticed in the original windows which I did not need replaced, the internal glazing bars are the same size of the outer most bars. However, as described in my original post, the newer panes have smaller bars in the centre of the window. Would you be aware of the reason for the difference?

The newer duplex bars vibrate when a car engine is running outside of the window....

Yes, I have astragal bars stuck onto the outside of the window with black foam tape.
Ok, I just wondered if it was those rattling , as some uPVC manufacturers only put tape on at varying intervals. I can only make an assumption that the original sealed units were made before Astragal bars were widely used , as some of the earlier ones did have the duplex bar the same size as the main spacer bar. Once energy ratings were introduced and the issues of heat transference recognised and needing minimising the duplex bars were made to no longer touch the glass. I do wonder what type of ' crucifix '/joining piece you have, as more I think about this , the more I remember it is the crucifix that normally stops them rattling , and is made out of plastic so heat transferrence is at a Minimum. As far as I am aware there is no reason for the duplex to be rattling... Certainly not just in response to a car idling
I've attached a photo of the type of glazing bars which were in the older glass which were replaced (approx 10yrs old), due to issues with the original installation. Does this provide any indication of what the older type of bars which were used?

The new bars are definitely duplex, which when the astragal bars are removed, you can see the two invidiual bars running parallel with each other to the centre piece.

Could the issue be with the method of how the galzing units were actually installed and not actually with the unit themselves? As I do notice some panes rattle worse than others of similar size.

I really appreciate your help!


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Well the old one is one solid piece so I can see why it doesn't rattle. The newer ones will be two separate bars, back to back, I find it hard to believe that the way they are glazed would cause the problem. Honestly I am at a loss as to why yours are rattling'
Happy new year...

Would the number of nails along the external slips of the windows make the glazing anymore stable and less prone to vibration?

I have two windows of the same size in two different rooms, one with four nails down the vertical slips holding the glazing in place (attached), which does not rattle as much as the one with only two nails (top and bottom).
In theory it should make no difference to the glass unit as the sealant will hold the pane of glass to the spacer bar. I would get more nails ( sheradised pins ) on though, as unless that is a very short bead then that would not be enough to glaze with. As a rough guide, I'd say a 600mm bead should have 4 pins...stops the bead from contracting and expanding too much. It does make me wonder whether maybe its the actual bead making the noise, would all depend on how it's glazed

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