Abhishek Chhabra is an Engineer and a Post Graduate Diploma holder in Finance. He has been advocating the need for compliance to standards for improved Safety and Quality across industries for most of the last two decades. He has vast experience of promoting conformity assessment in several industries. He has worked on several Standards and Codes development initiatives, specifically with Bureau of Indian Standards (BIS), ASTM, UAE Fire & Life Safety Code of Practice and Saudi Standards, Metrology and Quality Organization (SASO).
He joined Thomas Bell-Wright International Consultants in 2013 and has been the driving force behind the expansion of the Fire Compliance activities.
He also owns and drives a blog and a LinkedIn group called Gurus of Testing, Inspection and Certification (www.tic.guru) aimed at expanding the understanding of conformity across the world.
What is the critical factor in determining the fire-safety of a glass façade?
The starting point to answer this question is the occupancy type of the building which has a glass façade. The type of building (mall / school / hospital / residential tower / office complex, etc.) is what dictates the readiness of the people whose lives in would be in danger in case of a fire and what else might be at risk of the fire. These are among the several key factors that form the basis of Fire-Safety strategy or plan. They help formulate building regulations or guideline documents (Building codes) which are used in more evolved regions in the world.
A glass façade like most of the facades have replaced what used to be traditional load-bearing walls more than 50 years ago. They used to undertake several functions as in the image 01 here. These functions as often undertaken by several components. The key fire safety strategy (of passive fire protection) is implemented by compartmentalizing a fire within the place where it originates. When the building has a glass façade the most important considerations in ensuring fire safety is compartmentation. This has to be mainly realized at the floor to wall joint (spandrel section) to ensure that the fire can be contained within the floor and does not break into the floors above or below. Fire propagation across the fascia of a pure glass façade is only a matter of concern when there are other elements across the glass façade that could carry a flame or a fire. In certain occupancy types the glass façade also needs to act as the fire containment wall and here these is a fire rated glazing system. We know that the permutations and combinations of raw materials or components that build up a glass façade can be really large. So it becomes critical that assurance mechanisms of the supply of raw materials and components as well as workmanship of installers are very stringent!
What is the individual rating of the components of a typical glass façade, i.e. glass, aluminium, silicone etc.?
The individual response of components like Glass, Aluminium (Grade), Silicone, etc. in a fire or a scenario that could create a fire is very important (For Glass facades and not for other cladding types).
But these individual (reaction to fire or resistance to fire) ratings are meaningless without the assessment of a system behavior. This has been part of the steep learning curve that industry and governments have been imbibing in recent times.
Reading further from the initial question’s answer then, the real proof of performance of these components for Fire Safety lies only in how they behaved when they are part of a system. The tests would typically be Fire Resistance test used for evaluating compartmentation (ASTM E2307, ASTM 2874, EN 1364-3, EN 1364-4, etc.).
The small-scale reaction to fire classifications like as per EN 13501-1 or ASTM E84 then are only indicative of how they could contribute or react to a fire or fire like environment.
Does the paint on aluminium contribute on fire? And what about anodization?
Pure solid metals when used a façade material are very harmless from a Fire Safety perspective as they are non-combustible. But coatings and paints take these into a different direction. Any organic compound used would have a propensity to contribute to a fire due to its chemical composition. Hence Solid Metal Façade Materials initially thought to be very safe started being reconsidered as they were getting tested for reaction to Fire Classifications.
I can share that just because of the what is on a Solid Metal Cladding Sheet, the Reaction to Fire properties could be class B or C or worse even. Refer to Image 02 for better understanding of these Classifications. As for anodization the answer is straight: as long as no organic compound is coming on-to a metal; we are ok.
We see that countries have many different fire regulations. Does it happen that a particular assembly / product achieves the highest rating in one country but is rejected in another?
Unfortunately, the answer is no. And that is mainly because there is not world-wide agreement on what is highest rating!
Can you tell us a few things on full scale fire tests? What is the difference between e.g. NFPA 285 and BS 8414?
This is a tough to try in a small post as they are completely different approaches to evaluate fire propagation performance.
To start with the geometry and mock-up configuration are completely different. The list continues on mock-up methodology, type of ignition source; measurement methodologies as well as assessment of pass or fail. But this is the case with 20 plus test methods that have been evolving around the world. And unfortunately, more are evolving and getting published.
While both these methods have been revised recently, I must share that the BS 8414 Test Methods are only Test Methods. They utilize another published document BR 135 to assess the results of the test method to give an opinion on weather the mock-up system should be considered safe or not.
This document, the BR 135 (Fire performance of External Thermal Insulation for Walls of Multi-storey buildings) has not yet been revised since the test methods of BS 8414 where a level 3 was added among other changes.
In comparison the American method is very crisp and clear about pass and fail criteria. From a commercial lab’s point of view, the American test method uses gas fired sources of ignition and allow mock-ups to be built on movable test frames. This makes it easier to conduct larger number of tests. That said, both tests lead to great insights into the fire propagation response of mock-up systems and both are extremely invaluable for Façade Fire Consultants as well as regulators and other stakeholders wanting to create boundaries of what is acceptable and what is not.
Anyone looking to select one of the two should read through what all these two methods capture and consider drawing upon the observations and results of both to arrive at specific requirements for their projects or jurisdictions.