Façade is one of the most vulnerable elements of a building, especially in case of a fire incident. With more attention to aesthetics, cost factor, energy efficiency, eye-catching materials, green concept, etc., considerations of fire safety measures have been slipped under the radar. The scenario has become more complex with the unstoppable mushrooming of high-rise buildings which pose a greater fire hazard. In India, there are numerous fire safety related codes and standards, however, they are scarcely followed. Worse is the case when it comes to facades, it is mostly influenced by the pure considerations of alluring appearance and pricing, and is yet to hit the nail on the head in terms of fire safety norms and testing methods.
The majority of the population is still ignorant of the performance of the material and design of the façade play a decisive role in controlling or propagating the spread of fire. There is an acute lack of awareness about the characteristics of the façade materials, such as combustibility, smoke release, toxicity, ignitability, etc. that contribute to massive fire proliferation. Therefore, an active involvement of fire experts from design through to construction is very significant to help in deciding the right material for façade and correct use of these materials. Besides, all stakeholders should be thoughtful of the fact that combat against potential fire hazards can only be effective when façade systems/ testings are given due importance. This article will focus on the holistic analysis of the performance of façade materials, aspects of façade design for fire safety, fire testing of façade materials, the importance of compartmentalisation and more.
There are two main methods to prepare buildings for fire. One is to detect and act (passive fire protection) which uses detectors, annunciators, sprinklers etc., and the second method is to contain and restrict fire in a given location. Here reaction to fire properties and resistance to fire properties are used to contain or create a compartment. This helps in minimizing damage and evacuation to save lives.
Correct material selection and system design are the two key elements that form the basis of fire safety of a façade system. Abhishek Chhabra, Market Development Manager, Thomas Bell-Wright International Consultants, says, “Façade engineers designing fire safe cladding system need to know the fire properties of the material being used and their key reaction to fire like ignitability, combustibility, flame spread, and reactions of droplets and smoke. This basic knowledge is used to design a system, keeping in mind the net fire properties when given materials are adjacent to each other.
Emphasizing on the importance of fire resistant materials, Harish Gupta, Façade Consultant, Habitat n Skins, says that façade is the exterior wall of a structure or simply put a layer over a structural skeleton framework of a building. Its primary aim is to protect the interiors from wind, heat, cold, water and intrusion. Having defined this, fire resistance is very much a part of the principal functions of the building skin. “So a facade must not propagate fire, it must also not let the fire or heat travel from one area to another and it should not disintegrate in the presence of fire for a reasonable amount of time”. He highlights, “It is seen from many building fires that the spread of fire is spontaneous if facades have combustible materials and so every material that goes into a façade must comply with the minimum fire resistance required for an exterior envelope”.
Echoing the same view, Rahul Tyagi, Managing Director, RT & Associates (P) Ltd, adds that the major parameters for facade design against fire safety are that the material should be fire retardant. “In case of fire, it should be a deterrent for fire propagation and even if it gets burnt then it should not release toxic gases. It should be able to resist fire for at least 1 to 2 hours so that firefighting measures and human evacuation is possible”.
Sreenivas Narayanan, Façade Specification and Compliance Officer, Siderise Insulation Limited -The Middle East and India says, “The compartmentation based on fire and life strategy of the building will need to be followed for façade design. Separation of floors and two different occupants are primary and compartmentation within external façade assemblies like (cladding, stone, grc, hpl) with fire breaks to limit the chimney is also important.” Facades are not merely for an aesthetic consumption, they are also a sheath of protection from external stigma. The advent of modern contemporary materials has put forth a barrage of innovative technologies that propound a utilitarian approach without compromising the aesthetics of the fascia.
Badrinath Kaleru, Founder, Studio Ardete, puts in, “While designing a facade, it becomes imperative that we meticulously consider the inherent properties of these materials for a safe and efficient facade, considering the properties like thermal movements, the extent of smoke emission, etc”.
Physical behaviours of types of facade differ since their components, materials, and construction methods are different. Facade design can act as a passive measure to enhance the fire safety standard of any built form, for example – a facade can schematically incorporate rescue lobbies aiding firefighting, says Kaleru. “The challenge is to determine a facade design that trades off both the goals of efficiency and safety whilst allowing room for creative aesthetic decisions”, he adds. The key idea is to think of efficient infrastructure, not as a technology that is distinct from architecture, but rather as a new set of materials with which architecture can be made. Chhabra too opines that correct design and its proper installation are as important as specifying the right materials.
The fire safety of the building is dependent on the choice of each and every material that is selected and constructed to be part of the building structure. Any material that is in the direct line of fire and unprotected can propagate fire to other parts of the structure. Facade design needs to be done in a manner that it does not allow the fire to spread from one compartment to another. Gupta, stresses, “Facade as a complete system must not fail when a fire occurs. Even if the material selected is all fire proof or fire retardant, it’s the construction method or the assembly that needs greater attention. Easier said than done, as facade envelopes a building like a skin, in most cases with walls and beams touching it from the inside and the gaps between the skin and the structure are often given less attention, which is where the failure occurs even if the facade itself may be fire proof. A chain is weak only as its weak link and the gaps are the weak points in the facade design”.
As per the new regulations and awareness on safety in case of fire inside the building, says Varghese PV, CEO, Glazing and Metal Works, SOBHA Ltd., the following aspects are very important: • A sufficient number of openable panels to be provided (about 10 percent of total vision glasses) to avoid hazard due to smoke in case of fire. This is to help to ventilate the area. • Fire stops between the floors on the periphery in order to check the fire in the floor itself. • Enough ventilated staircase or pressurised staircase is a must to provide safe movement in case of fire. • Discourage the use of toxic materials inside, like normal aluminium composite panel • Provide the sufficient refuge areas as per requirement to facilitate the rescue.
There is an endless launch of new materials and façade systems in the market, however, it underlines the reliability, quality and safety of these products. It calls for proper testing and regulation methods to enable the evaluation of a façade’s fire-spread capacity. Giving the bleak picture in the hands of the manufactures, Chhabra explains that the most unique aspect of (fire) testing of (façade) materials is that the manufacturers can fool anyone easily by providing test reports for their material. This can be done by making a “Golden Sample” pass all the tests with flying colours. And then in the factory, raw materials, recipes and processes could change due to errors or price constraints. Certification and listing introduce surveillance and traceability of supply chains and processes to add many layers of checks.
Fire testing of the building facade material critically determines the viability of the facade in accordance with the context, safety standards, efficiency and the overall environmental impact including smoke emissions and weather resistance. A large scale testing of varied components may decrease the extent of these catastrophes, puts in Kaleru.
A variety of innovative and unique technologies and materials call the necessity of different test methods to gauge the performance of various façade systems/elements. Chhabra, elaborates, “Properties of ignitability, combustibility, flame spread and other reactions of droplets and smoke are measured using different test methods. One of the comprehensive methods is the Euro-classes classification that uses EN 13501-1. This captures and tabulates the properties of combustibility, smoke and droplet release. Many other test methods like ASTM D1929 for capturing ignition temperature of plastic, ASTM E84 for capturing flame spread and smoke developed are useful for analysing certain types of materials”.
The certification is generally provided a third party accreditation providers. Eg. Intertek, Certifire, UL etc. These bodies, inspect the materials under production, witness the test and compliance to the standard set and issue certification for the suitability of the application. The certifying bodies also carry out a periodic audit of the certified products, says Narayanan.
The performance expected out of most building materials from fire point is its resistance to fire and not combustibility alone. According to Gupta, “The resistance time that a material offers counts towards the disintegration of the material, the rate of spread of fire and the valuable escape time it gives the occupant before it is out of control. The facade material should surely not propagate fire. Further, it should be able to offer a minimum of 30 minutes to two hour fire resistance, depending on the distance from the source of fire calculated or resistance required. Since it is the outer skin, fire can easily spread to multiple floors very quickly as there is no scarcity of oxygen in the outside environment. When we choose the facade material, we must keep in mind that they are non-combustible and should not propagate fire like aluminium composite panels, PU foam metal panels, insulation that is petrochemical based, etc.” He further adds, facade material can be classified based on certain lab tests as ‘B’ class or ‘A’ class and their sub classes. ‘A’ class being the highest for a non-combustible material and assembly with such material is not easy to achieve in a facade. It comes at a huge cost which the promoters can hardly afford on a large scale. However, where fireproof enclosure is absolutely essential, the specification needs to adhere to ‘A’ class.
All material used in the construction has to be fire proof and the structure must retain its integrity for a min of 30 min as per NFPA 285 code for fire resistance of facades. Having said that aluminium has a very poor fire resistance as it melts at 660 0C and anything held by aluminum frames, whether fire proof or not, will disintegrate within a short time. “So while specifying fire rated material, one needs to keep the entire assembly in mind and every material that goes into the making of a fire rated facade must have fire resistance as desired,” points out Gupta.
“Physical and mechanical properties like thermal conductivity, thermal movements, etc. give an astute sense of the performance of facade materials during the fire. Rigorous fire safety tests need to be employed to determine those properties accurately. The surface spread of fire with regards to the combustion of the facade material, the fire spread within the facade material, melting of the internal insulation, etc. are some of the parameters that guide both the design and the performance of a façade,” explains Kaleru.
Giving an interesting view of the performance parameters, Narayanan points out, “Different products will have different parameters for performance requirements. External façade materials like cladding will need to have the classification through an EN 13501 test, e.g. non-combustible, limited combustibility, combustible, etc. Combustible materials should not be used on facades. Both Narayanan and Chhabra agree that the net sum property relation to fire needs to be validated using one or more large scale fire propagation tests of the mock-up of a cladding system like the NFPA 285 or the BS 8414 or others.
The fire properties of a material are an important aspect which can prevent the spread of fire. Materials with low thermal transference and higher fire ratings shall be used to enhance fire safety. “Additionally, a facade can act as a buffer to stop the fire from entering inside the structure while facilitating firefighting,” says Kaleru.
Chhabra explains, “One, correct material needs to be selected, and certification and listing are used to ensure that the correct material is reaching the site. Two, one or more large scale mock-up tests need to be conducted to validate the design of the system which will be implemented at the site”. Lastly, he emphasizes on thorough installation inspection to keep a check on the quality and replicability of the installation. Use of combustible materials is the primary cause of fire spread. Floor to floor compartmentation at the perimeter edge of slab and curtain wall (which is also mandated on the India NBC 2016) is important to stop the spread of fire internally. The chimney within the cavity walls should have a fire break or a barrier to reduce the fire spread, says Narayanan.
Fire rated glass system is needed only if compartmentalization is needed as a part of the fire strategy of a building, says Chhabra. Fire propagation on the surface of the building depends on fire resistance property of the material used. According to Gupta, fire rated glass is expensive. “But we don’t have to design the entire facade with it. Depending upon where it is used we can choose between a different rated glass,” says Gupta. Fire rated glass come from 30 to 120 minutes and more. One may think that 120 minutes is the best, but it is very expensive and one can avoid it with intelligent use. 120 minute glass should be used for escape routes or assembly area segregation, which is rarely a part of the facade
For façade, a 30 minute fire rated glass with a fire rated assembly may prove just the solution. But it’s up to the designer and the client to take a call on the extent of use of such glass on the facade. Also, it makes more sense to see what other elements are used in the facade with glass. If you have consciously avoided any combustible material in the facade than even a 30 minute fire rated glass may give a very good fire resistance to the exterior envelope and also keep the costs from getting ridiculous. It’s worthwhile and high time that developers spend that money on tests like NFPA 285 to understand what they are constructing before its too late. There is no substitute for a fire rated glass as yet. When you need to see through function and you need it fire rated than glass is the only material that fits the description.
However, Varghese holds a different perception about fire rated glass. Using fire rated glass for the outer facade is not practical as it will cost a huge amount. The difference is like 8 to 10 times, so is the delivery time. “Fire rated glass for exteriors is not important as the inside fire make causalities more by smoke than the fire. We need to have a smart facade which can ventilate in case of fire and smoke inside,” he adds. However, he emphasizes that in case of lift lobbies where peoples movement are restricted during fire and smoke, fire rated glass should be used for partitions which will serve the purpose. This will be affordable too, since the area of each lift lobby partition is very less compared to the facade area. According to Narayanan, if the curtain wall framing is not fire rated, the glass, even if it is fire rated, will not have any effect. I do not think it will be economical to have a fire rated system as a curtain wall for highrise, as per Narayanan.
Talking about the pricing of the fire rated glass, Tyagi says that affordability depends on the importance of building versus fire safety. However, fire rated glass is becoming more and more affordable now due to increase in production and usage, he adds. According to Kaleru, fire rated glass can protect an area for several hours as compared to the non-rated counterparts, reducing the spread of fire. It prevents an imminent threat to life and other assets. The affordability depends on the type of fire rated glass product and the degree of fire resistance. A wide variety of specially tempered glazing and wired products are available, but they all have a certain limitation. So it becomes really important to understand and conform to building codes that elucidate the use of fire rated products.
A fire stop is a sublime fire protection measure which seals openings and joints in a fire rated wall, minimising fire escalation. They hinder the transference of smoke and fire through cracks and crevices in walls and floor assembly. These are available in varied forms and materials like cementitious mortar, silicone, rubber, etc. Fire stops materials and systems are used to ensure the fire is contained within the compartment created as part of the fire resistance strategy. Any areas like through penetrations and parts of cladding system create gaps and openings in the compartments designed to contain the fire. “Fire stopping systems are tested and listed for specific material combinations and designs. They are needed to be selected and used with extreme caution. A fire stopping system tested in a given combination being installed wrongly or in a different combination can be ineffective,” says Chhabra.
According to Varghese, fire stops play a very important role in fire safety to check the fire and smoke
in confined area/floor of the fire. Usually, they are in 3 major areas: • Between the floor edge and façade, which will help the fire and smoke to confine to the floor of the fire avoiding spreading vertically upwards to the next floors; • Between facade and cabin partitions, which is vertically. between the column and facade or partition and facade which will check the fire and smoke from spreading on the same floor; • In service shafts which helps in isolating each floor and restrict the smoke spreading through the shaft vertically up to the other floors. This is applicable to all service shafts like fire shaft, AC duct shaft, electrical shaft and air vents if any. The space left after the service pipes should be treated with appropriate fire proof sealing materials.
As part of the construction of One and Two Island City Center (ICC) towers in Dadar (EAST), Mumbai – reaching 64 floors and 72 floors respectively – the specification of a slab edge perimeter fire barrier will seal the void between the floor slab and the external curtain wall and vertical compartmentation between two different occupants.
With both vertical and horizontal fire compartmentation requirements of this fast-track project, the specification of SIDERISE CW-FS 120 firestops has provided the façade contractor Alumayer India Pvt Ltd and Alufit (India) Private Ltd with a solution that could maintain a fire and smoke seal in one product preventing the passage of flames and noxious gases passing from one floor to the next and also for vertical compartmentation.
For the two residential towers, the façade contractors installed circa 5000 LM of SIDERISE CW-FS 120 firestops including horizontal (floor slab) and vertical compartmentation. With the timeline on the project critical, the use of this dry fix system enabled the work to be completed quickly and efficiently, ready for handover to other subcontractors.
There is a common misconception between the smoke stop and fire stop. Both are different. The fire stops are an expensive product and are essentially put in electrical shafts to seal at floor levels or are between compartments above the false ceiling level where services cross. But when it comes to facades, it’s actually used only on very few projects and a lesser alternative called a smoke stop is used. The smoke stop is much cheaper and only stops the smoke. A fire stop for facade makes sense only if the facade is also fire rated to some extent. So when we do provide a fire rated façade, then we have to use a fire stop to make the whole assembly fire retardant. Fire stop or smoke stop is the filler material or construction between the façade and the structure. Vertical or horizontal, all facades will have gaps at interface junctions and this is where the smoke and fire stop needs to be used. It acts as the barrier for fire or smoke to travel from one compartment to the other adjacent or vertical compartment.
Compartmentalisation in the structure is incredibly crucial for the containment of a fire hazard and allowing for a safe egress to the nearest exit point or a rescue lobby. It is the measure that will stop the fire from travelling from one zone to the other thereby preventing the spread of fire. Kaleru, says that the basic idea is the subdivision of a large internal space into multiple microcosms by fire rated partitions to impede the spread of fire, flue gases, heat, etc., limiting the damage caused to a building and its contents. “Compartmentalization depends on various factors, including the fire load of a building, availability of the sprinkler systems, the height of the building, etc.”
As per Gupta, “Compartmentalisation is absolutely essential. Fires must be contained in the original compartment it started as far as possible, preferably for minimum 30 min if not 2 hours in an ideal condition which allows enough time for occupants to escape and the fire authorities to extinguish the fire. If not contained, fire can destroy the entire building within minutes as has been seen in many building fires, especially the ones with ACP cladding.” Compartmentalization helps in restricting the spread of fire in the building, it localizes the fire and helps in early detection and firefighting. It also ensures that people are evacuated safely from other areas, says Tyagi.
Globally, the awareness of fire and life safety has multiplied in recent time. The stakeholders have been very cautious in choosing the right products with tested systems and accreditation. The installation of the tested systems has to be installed rightly on projects which are also monitored closely by the stakeholders, says Narayanan. In India, awareness of the dangers of fire is there, but the approach to prevent it is absent. There are strict fire prevention and firefighting norms like sprinklers, fire doors, wet risers, fire alarm system, smoke detectors, fire escapes, etc. Fire rating for facades has remained fairly absent from building regulations even though there are codes and tests as per BS 8414 part A and B and NFPA 285 and that is the reason no one following it. Gupta gives an interesting insight that when it comes to façade, the fire regulations are virtually silent about being strict and gives a free hand to developers and architects to design as per their wish with no authority pinning them down on the fire safety aspect. But it’s high time all stakeholders give it a serious thought as no amount of passive firefighting can ensure a 100 percent fire proof building if its facade is still vulnerable.
Highlighting on the positive development, Tyagi chips in that prominent builders/developers/ architects are very much conscious about fire safety. No building is approved/constructed without adherence to fire safety norms and fire department NOC. The stake holders do realise the importance of human life and the importance of fire safety and invest in it.
But, according to Varghese, many new norms specified in the latest edition of NBC are very difficult to follow word by word. The builders and architects are very conscious in their approach. They are finding ways and means to adhere since all are agreeing that the enforcement will be stringent in future. “We are finding these norms strictly applied in commercial buildings and bigger residential projects. Even norms on refugee area requirements are getting high importance unlike earlier”, he adds.
Taking into account the high profile fire incidents around the world, architects, contractors, developers, façade engineers, fire-testing laboratories, etc., are becoming more aware of the need of unified building fire safety codes and standards and hazards of combustible substandard materials. However, the industry has to be more vigorous by organizing more awareness seminars/conferences to address the issues at the highest level and educate the stakeholders of the dos/don’ts to curb the potential Façade of a Project by Studio Ardete fire risks.