Following our "Debate on Laminate Glass" virtual event. We have compiled the below questions and provided answers from the panel.
1. Are there any alternative products in development that will comply?
We are not aware of any, as there seems to be little appetite from the laminate providers as it is most likely seen as an impossibility.
2. What testing has been completed on laminate glass to see if it meets the required classification? Is any data available?
Several laminate glass tests have been carried out to establish the reaction to radiant heat. Not surprisingly, when a leaf breaks, the interlayer burns for a very short time until it is consumed with a standard 1.5mm thick interlayer. This is no different from the waterproof building membrane - which is not banned. Our argument is that the interlayer does not present a likely ignition source and that it is not a significant fire load contributor.
3. Does laminate glass contribute to fire spread
During a Sapphire internal test to attempt the ignition of the interlayer, whilst it did ignite with a linear gas burner beneath it and centred on the laminate, the glass did not crack, there was some minor flame and some bubbling of the interlayer between the two leaves of glass but the flame died away with the burner removed. More severe radiant testing has shown that the gasses produced when a leaf shatters produces sustained flame but due to the very limited thickness it lasted a very short time in the intense heat. Therefore, we do not feel that laminate glass contributes a significant fire load.
4. Is there a clear fire-retardant interlayer that will resolve this issue, though it might drive up costs?
Unfortunately, not. Even interlayers which perform well in fire partitioning internally do not meet the criteria of being Class A, and most are also not UV stable.
5. Will a bottom channel bonded onto the panel prevent burning droplets and satisfy concerns assuming a fire-retardant adhesive can be sourced?
If a floor or wall mounted channel is used for balustrade purposes and the panel is wedge fitted using aluminium wedges, this would be a reasonable solution. In most balcony situations, the bottom portion of the panel is often somewhat shielded in any case. Unfortunately, although it may seem practical to suggest adding a channel may avoid fire damage, unfortunately, it does not make the laminate class A.
6. Is the issue that if the interlayer is compromised the outer layer of the laminated glass unit falls away? If so, has a through fixing to clamp the layers of glass together been researched?
The issue is principally combustibility. Using a mechanical connection passing through the bottom of the glass and having a handrail/capping at the top are both things which help reduce this risk.
7. Should we focus more on fire prevention?
Yes. We agree that stopping this initially is key and education is probably the first part which needs addressing. See our article on combustible items to avoid using on your balcony which was produced in conjunction with the Manchester Fire Brigade.
8. What are other credible research is being completed on laminate?
The London Underground has taken a position on laminate glass which is key to the construction industry. Titled ““G085 Code of practice - Fire Safety of Materials and Fire Safety of Specific Items and Materials Used in the Underground”” See below:
9. Is there a modern version of Georgian Wire that can be applied to 19mm thick monolithic glass so will be structural?
Structural monolithic glass needs to be toughened to withstand the forces which it will be subject to. The normal loading requirement is 0.74kN at 1100mm height from deck level. We are not aware that it is possible to wire toughened glass. Glass companies do not like to float, process, or toughen and it is actually very tricky to get hold of now, regardless of being wired or not.
10. Is the ban on laminated glass applied retrospectively as rain screen cladding is, & will have to be replaced with toughened glass balustrading?
No. Even buildings which were given permission prior to December 2018 (check date) can continue its use for that development and there is no requirement for retrospective remedy. It does not seem like it is considered a risk enough for the government to enforce like cladding was.
11. In the laminate whitepaper it shows the monolithic glass smashing. What could residents do to ensure fire safety on their balcony?
There are two choices for the resident. Firstly, what they put on their balcony and secondly what they do on their balcony.
If users have metal furniture and do not smoke etc. then the fire risk is very low, if however, they have bamboo screens and wooden furniture whilst having a BBQ they are probably likely to have a high fire risk/probability.
Try and ensure that combustible furniture and other items do not stay out on the balcony. Use an electric BBQ if you want to use your balcony for this purpose. Have a fire extinguisher to hand in case of trouble. Be vigilant. Cases of balconies catching fire are small and it mostly comes down to some careless event if a fire is started.
Many building owners are looking at replacing such things as timber decking, combustible cladding adjacent to the balcony etc. this would clearly make a big difference. It is more difficult if the joisting is timber but not impossible to replace this.
12. A fire-resistant interlayer exists, why can’t we use that?
It needs to be understood that there are plenty of products with reduced combustibility, but the building regulation require class A1 or A2 - a stringent requirement. Any fire-resistant product would need to be tested and certified to this standard to conform in the UK.
There are various interlayers we have tested like this which help the fire resistance however none we are aware of have been non-combustible.
13. Are there any types of laminate glass that should remain banned?
One area which would merit investigation is the instance sometimes of multilayer interlayers. It is very common for up to 4 very thin interlayers to be bonded together to form a 1.5mm thick standard thickness and this essentially presents no problem in our view. However, it would be feasible to have a much thicker interlayer too and it is likely that a point may be reached where the interlayer does indeed present more of a fire load if not an ignition risk.
There is a minimum thickness of interlayer needed to make it work effectively with the natural 'roller wave' of glass panels (toughening process distortion), there is also a maximum where too much interlayer would mean that the panels aren't providing so much synergistic strength. Perhaps there should be a max limit, e.g. 4/5mm max interlayer thickness.
In terms of interlayer types, all those tested in our research, showed little difference to fire load, all were minor because of oxygen starvation.
14. Is there existing physical fire test data available to MHCLG that demonstrates laminated glass does not contribute to fire spread?
Our position is that laminate glass does not contribute significantly to the fire load. Spread of flame is obviously an important issue but a different one, and our tests on this front indicated that the likelihood of fire spread from laminate glass is very unlikely due to the interlayer being largely shielded by the glass leaves. However, it should be bourn in mind that allowable items to facades such as the waterproof membrane, and cavity trays would be a far greater contributor to spread of flame than laminated glass could possibly be.
It should also be remembered that with all balconies and facades now requiring a class A1 or A2 rating, the instance of a raging inferno up the side of a building which we witnessed at Grenfell is almost entirely removed. A fire instance now would need to be furniture placed on the balcony or a breakout of fire from within the property. Neither of these are as likely to produce a whole facade inferno.
The whitepaper we produced for laminate glass was created for the MHCLG and the tests were done to show each element and scenario so that there was a holistic view of fire spread in both unlikely scenarios, worst-case scenarios and in actual incidents.