The newspapers have had their say, the politicians have spoken, and now it is time for a judge to make some sense of what happened that terrible night at Grenfell Tower. The building industry eagerly awaits the report and its implications for the future.
In the meantime, knees are understandably jerking out of control as cladding and insulation are stripped from our high-rise edifices across the nation.
Many experts in the industry had predicted the consequences of wrapping buildings with highly inflammable materials, but it appears that regulations may have allowed them to be used under the flimsy guise of Class O flame spread certification.
All we can say is that what we thought was safe clearly was not. Perhaps adhering to fire regulations has slipped. Looking back though, we should not have been too surprised. Towering infernos are nothing new, there have been several in recent years, and the finger of blame has been pointed to the cladding on many occasions, most significantly in The Address hotel in Dubai 2016. There have also been incidents at The Lacrosse Building in Melbourne 2014, Mermoz Tower, Roubaix, in 2013, and Al-Tayer Building in Sharjah, 2011.
In spite of the arguments about cladding and insulation, there is an elephant in the room that no-one has so far tackled. What was the real cause of the fire spreading to cladding? The answer is a known to firefighters as ‘Autoexposure’ or ‘External Fire Spread’.
These are terms used to describe the spreading of external vertical fires. Primarily, it is about how heat and flame spread from a lower window to the one above it. A fire usually begins in the content of the room, and then spreads from window to window. The heat of the fire causes the glass to shatter, and the window frames to melt, enabling the fire to lick up the side of a building at increased speed. This then becomes known as a ‘structural fire’, which is significantly more difficult to tackle than a contained internal fire.
The principle of ‘flashover’ can then occur where heated cladding or insulation material gives off flammable gases spreading the fire continuously upwards. The ‘Coanda’ effect draws the hot gases and smoke closely against the side building. The upward action is relentless and extremely fast. The result at Grenfell is scorched in our minds, forever.
Cladding and insulation can only ignite if the fire surges out of a window, leading to a rapid conflagration, leading to catastrophe. Therefore, the problem it is clear, begins at the window. If we can stop the fire getting out of the window, then we may have a solution. If we can provide an effective fire-resistant window, then the fire will be contained in the apartment or flat.
The philosophy of Compartmentalisation has been proselytized throughout the industry for many years, but it seems that on high rise design, the outside wall is always ignored as they are typically designed with standard commercial non-fire rated windows. How can a plastic or aluminium window with regular glass create a fire compartment? It simply can’t. Internal fire compartments, such as internal atria or partitions, make use of steel framed window or façade systems with fire rated glass, and this should be the same for external windows and glass.
An issue that needs to be addressed is the problem of windows being left open, which render them useless in the event of a fire, even if they are fire-resistant. It is the same issue that we have with fire doors. The solution is simple, closing mechanisms can be fitted which operate on a signal from a fire alarm.
Following the well-known New Year’s Eve fire in Dubai in 2016, Pensher Skytech developed a sliding fire-resistant window which does exactly that, it closes automatically when the fire alarm is sounded. The window has been fire tested to EN1634 and to UL standards and is fire rated for 1 hour for integrity and insulation.
In these types of windows, ventilation can often be seen as an issue, however, we have ensured that the window can be mechanically or electrically operated for general use, allowing access to fresh air when it is needed.
Although it has not been common in the building industry to fit fire glazing externally, it is becoming an increasing requirement, particularly overseas. Many of our projects have been petrochemical sites, where the fire can be a threat to the external of the building. The windows are designed to prevent the fire spreading by ensuring it does not become external, which would enable the fire to climb quicker up the building. By keeping the fire contained, it will protect more lives inside.
It has always seemed strange to a company like ours that fire-resistant windows are not a requirement in high-rise buildings, as it seems obvious that, though they are more of an expense than commercial windows, they offer much more protection and are more likely to save lives and infrastructure from the threat of a fire. Perhaps there needs to be more knowledge on this made generally available to the public. Unfortunately, it sometimes needs a ‘Titanic’ moment to happen to make people think differently about what can be done to prevent the tragic loss of life.
For any queries on fire safety, fire protection, or for more information on Pensher Skytech’s fire-resistant windows, please don’t hesitate to get in touch.
This article was written by our Technical Manager, Derek Quinn. Derek is responsible for designing and developing our high specification doors, windows and glazing systems to protect against physical threat. This threat can be ballistic, blast pressure, physical attack, or fire. His knowledge and experience from working for over twenty years in the sector enables him to direct our product development, particularly in the fields of blast and fire protection.