Triple Glazing Install Issues

[EinTopaz]

Hi all,

 

We've recently had all the glass upgraded in a rear extension from standard double glazed (1.3 U value) to high thermal performant triple glazed acoustic (0.675 U value) in a hope to improve the room's ability to retain heat. 

It's been in a good few days now and frustratingly the room seems to be retaining heat worse than before!... i.e - It's dropping by more degrees over night than it did with the standard double glaze in previous.

Due to the huge difference in U value I started to think perhaps this could be down to a poor install? I'm not technical but took a closer look and found some things I wonder whether anyone on here would be able to confirm are a problem or not? list with images below.

 

 

 

 

• The units appear to sit very low in the frames, much lower than the units previous did.
  • I'm wondering if they're not sat on packers?  If they're sat so low could there be a massive gap at the top allowing coldness?... and could this damage the units and frames too?

 

 

 

 

 

 

 

 

 

 

• Some of the black unit framing is very visible on some of the windows.
  • If the unit is either fitted off-centre or if they've measured it wrong and made a unit too small, could this cause an issue?
  • The thermal cam did pick this up.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

• On one of the windows I can see they've put vertical packers between the glass and exterior frame
  • Again, could this be an issue letting draughts in? never seen this before, or is it fine to do this?

 

 

 

 

 

 

 

 

 

 

 

 

 

• Lastly, The beading has some play in it in certain parts of some of the windows.
  • previous double glaze had a thicker bead and was absolutely rock-solid, should there be this much play?

 

 

 

 

 

 

 

 

 

 

 

 

Is there anything in the above that looks like a no-no to anyone in here with an experienced eye? Not sure what I need to say to the fitter, if anything at all?

 

 

 

thanks

 

Ged

 

 

 

Edited Sunday at 21:17 by EinTopaz

[DamonHD]

For at least one of my 3G units the nominally-expert third-party fitters left a ~1cm gap down one side of the unit, which I only discovered sometime much later, so basic errors can happen...

[dpmiller]

blue square thing looks like a transit foam that hasn't been removed from the unit?

[Nick Laslett]

@EinTopaz, @craig is the forum member with a lot expertise on this topic. 

 

A 3G window will perform similar to a 2G unit if the gap between panes is too small, e.g. a 28mm unit will perform the same, whether 3G or 2G due to these gap sizes. For a good performing 3G unit the gap size needs to be 16mm as a minimum. 
 

*Apologies if my understanding on this topic has been superceded with more recent developments, very happy to be corrected by those better informed. 
 

Good discussion in this thread.

Edited Monday at 08:04 by Nick Laslett

[craig]

@EinTopaz

 

There's a couple of issues here tbh.

 

1. It appears the glass is too big by about 3/5mm in width and height, when measuring, it would appear the have measured from bead to bead and not deducted anything and not said anything, take a bead off, and if the glass is to the frame, with no packers, that's exactly what they have done and I would be requesting they correct their mistake. Any movement and with the glass not being correctly packed, could cause the glass unit to fail.
2. A double glazed unit will be 24, 26 or 28mm thickness, which consists usually of 2 x 4mm glass panes and 16, 18, 20mm spacer between the glass.  A triple glazed unit at 28mm thickness, isn't going to be much better than a modern 2g unit in all honesty. 
3. Blue packer / glazing foam transport as @dpmiller suggested, the size of packers are defined in colour coding as standard, blue is 5mm, if they have used a packer here but I would have preferred to see some glazing tape. The glass can be up directly against the frame without a packer or glazing tape but as long as the gasket meets the glass externally. Whether it is a packer or foam glazing protector, I suspect the gasket isn't meeting the frame. 
   1. green shims 1mm
   2. black shims 2mm
   3. white shims 3mm
   4. grey shims 4mm
   5. blue shims 5mm
   6. red shims 6mm
4. Movement in spacer, this ties into point 3, this packer of 5mm appears to be an attemp to pack the glass, so that internally you wouldn't see any difference but just a suspicion, is there a gap between the frame and glass externally? If yes, then it explains the movement in the glazing bead imho.
5. On the small angle, they have cut the bead to short and filled with silicone. 

Edited Monday at 08:43 by craig

[Redbeard]

16 hours ago, EinTopaz said:

(0.675 U value)

 

Really?

 

I realise that's glazing only but even that seems low if it's a 28mm unit. Is it, or have they used a smaller bead to give you a bigger rebate? (I know you can do that with Rehau 'double glazing' frames, up to as wide as 44mm - although someone from GBF who has done so said the tiny bead is a real bu**er to get in and out).

[EinTopaz]

10 hours ago, Nick Laslett said:

@EinTopaz, @craig is the forum member with a lot expertise on this topic. 

 

A 3G window will perform similar to a 2G unit if the gap between panes is too small, e.g. a 28mm unit will perform the same, whether 3G or 2G due to these gap sizes. For a good performing 3G unit the gap size needs to be 16mm as a minimum. 
 

*Apologies if my understanding on this topic has been superceded with more recent developments, very happy to be corrected by those better informed. 
 

Good discussion in this thread.

 

 

Thanks, I should've mentioned at the top of the thread. These are 38.8mm units. The older double glazed were 28mm. They used lower profile triple glazed beading to accomodate.  

make up of the triple glaze unit is 6.8mm lami at the front, 12mm cavity, 4mm planitherm one, 12mm cavity, 4mm planitherm one

 

[EinTopaz]

4 hours ago, Redbeard said:

 

Really?

 

I realise that's glazing only but even that seems low if it's a 28mm unit. Is it, or have they used a smaller bead to give you a bigger rebate? (I know you can do that with Rehau 'double glazing' frames, up to as wide as 44mm - although someone from GBF who has done so said the tiny bead is a real bu**er to get in and out).

Yeah, sorry I should've said in the thread at the top, these triple are 38.8mm thickness. Lower profile beads were used to accomodate the thicker units..... that's why im really shocked im not seeing an improvement here, original double glazed units were 28mm.

6.8/12/4/12/4 

Spec sheet attached.

 

[EinTopaz]

On 19/05/2025 at 09:41, craig said:

@EinTopaz

 

There's a couple of issues here tbh.

 

1. It appears the glass is too big by about 3/5mm in width and height, when measuring, it would appear the have measured from bead to bead and not deducted anything and not said anything, take a bead off, and if the glass is to the frame, with no packers, that's exactly what they have done and I would be requesting they correct their mistake. Any movement and with the glass not being correctly packed, could cause the glass unit to fail.
2. A double glazed unit will be 24, 26 or 28mm thickness, which consists usually of 2 x 4mm glass panes and 16, 18, 20mm spacer between the glass.  A triple glazed unit at 28mm thickness, isn't going to be much better than a modern 2g unit in all honesty. 
3. Blue packer / glazing foam transport as @dpmiller suggested, the size of packers are defined in colour coding as standard, blue is 5mm, if they have used a packer here but I would have preferred to see some glazing tape. The glass can be up directly against the frame without a packer or glazing tape but as long as the gasket meets the glass externally. Whether it is a packer or foam glazing protector, I suspect the gasket isn't meeting the frame. 
   1. green shims 1mm
   2. black shims 2mm
   3. white shims 3mm
   4. grey shims 4mm
   5. blue shims 5mm
   6. red shims 6mm
4. Movement in spacer, this ties into point 3, this packer of 5mm appears to be an attemp to pack the glass, so that internally you wouldn't see any difference but just a suspicion, is there a gap between the frame and glass externally? If yes, then it explains the movement in the glazing bead imho.
5. On the small angle, they have cut the bead to short and filled with silicone. 

Thanks for the in-depth reply Craig, appreciate that.

1. I hope not, I seem to recall the fitters on the day saying "there's a 20mm gap at the top" on one of the windows" which to my untrained ear sounded alot. I assumed they should overlap with the gaskets by 8-10mm?   i'm going to enlist someone independent and experienced with triple glazing to cast their eye over this.

2. Apologies, I should've laid this out in the thread. Original double glaze was 28mm. This acoustic triple is 38.8mm (6.8/12/4/12/4) The acoustic lami is on the outer and the two other pieces are planitherm one. Frames are deckeuninck 2500 type. We used a lower profile deceuninck bead to accomodate the thicker units. As recommended by deceuninck.

3. Not sure if gasket is meeting the frame, i'll need someone to confirm that. I think it is glazing foam as i found some of it on my drive that was identical in colour. Maybe it's been squished down loads.

4. same, not sure if gasket is meeting. But most of the beads are nice and tight, it's only a handful that have this much play in them, so confused at the inconsistency. Unless the glass hasn't gone in straight. I.e meets the top gasket but not the bottom one, etc. 

5. Yeah so on this, I suspected as much, however I have noticed that shaped piece of glass has been either fitted off centre, or wonky. The shape is a triangle, but i can see the tip of the tringle of the unit is about 4-5mm offset to the left. So looks like maybe this piece is too small. I'll need someone to confirm this too.