Cladding Choices

Over the years cladding industry has been going through a sea change. Along with a flood of innovative materials and designs introduced in the market, we see the advancement in technologies in application as well. As per a research report Grand View Research, Inc.’, the global cladding market is expected to reach USD 111.1 billion by 2025 and is projected to grow at a CAGR of 2.6 per cent from 2017 to 2025.

The increasing construction spending and the development of more efficient building technologies using automated production and installation processes are expected to foster industry growth. Stringent green building regulations and codes such as the LEED certification, and growing demand for energy efficiency in project exteriors, especially for key construction industry participants, including architects and designers, are encouraging investments in lightweight and energy-efficient exterior panels in commercial as well as residential buildings. The choice of cladding has a significant effect on the environmental performance of a building.

We spoke to several experts in the construction sector, including architects, façade consultants, manufacturers of cladding materials and builders on the advancement in the cladding sector, the newest in cladding technologies & materials, fire tests and fire performance of external cladding systems. Here is what experts have to say about the latest in the industry.

PURPOSE OF CLADDING

Cladding serves many purposes, including creating a controlled internal environment, protecting the building from external conditions, preventing the transmission of sound, for providing thermal insulation and improving the appearance of buildings, among other things, says Amit Shah, Managing Director, of Classic Marble Company.

Cladding maintains privacy and security of exteriors, provides access to ventilation and a hygienic environment and prevents the spread of fire. Basically, its properties like termite resistance, waterproofing nature, environmental friendliness, and wide range of colours & designs make cladding a trend, notes Rachhpal Kanwar, General Manager – Exterior Cladding and Cubicles, Stylam Industries.

The main functions of any cladding are to provide an enclosed area that will provide protection from an all-weather condition like rain, wind, or cyclone; also the safety of inhabitants is the major concern while designing a cladding system. According to Upendra Walinjkar, Director, Aluvision Façade Solutions Pvt Ltd., all these can only be achieved with very good structural and system design.

Alhad Patil, Technical Director, Diamond Metal Screens, observes that exterior cladding, especially perforated metal façades, plays an important role on the structural aspects of the building. Being generally lightweight in nature – due to perforations, they add minimal weight/sq m to the building, while adding a host of advantages such as ventilation, sun screening and more importantly dissipating heat absorbed structurally through the aluminium second skin.

According to Akash Saini, Director, Notion Flooring, cladding not only provides protection but also enhances the architectural concept and appearance of the building. Its impermeable and porous material helps to absorb water during rainfall and completely keeps out rain infiltration and keeps buildings secure and safe.

Importance of External Cladding in Buildings :

• Create a controlled centralised environment
• Protect the architecture from alien conditions
• Prevent the transmission of sound
• Provide thermal insulation
• Create an external façade
• Prevent the spread of fire
• Generate an ‘airtight’ architecture envelope for the building
• Provide openings for access, lights and ventilation

Structural Role of Cladding for Buildings

Cladding, even though essentially the non-structural secondary surface attached to the primary structural surface of the building, has a fitting effect structurally on the building, points out Prof. Charanjit S Shah, Founding Principal, Creative Group. Though it is merged with the primary face of the structure, it does not contribute to the stability on the whole. Regardless, it does play a structural role in transferring wind loads, impact loads and its own weight back to the structure which implies that an ample amount of strength is required both within the cladding system and its joiners for the primary face to ensure that it does not crumble under wind load pressures. Walinjkar too agrees with this statement.

According to Rohan Keswani, Director, Aluplex India Pvt Ltd, curtain walls and cladding materials are designed and engineered to withstand wind loads based on the topography and geometry of the building, the dead loads of the curtain wall, the live loads imposed, seismic loads and thermal loads, whilst also accounting for loads imposed on the cladding due to building movements such as column shortening and creep movement.

The cladding is designed to limit the deflections of the cladding framework and infill panels within serviceability limits, as desired. More importantly, design and engineering checks are carried out to ensure that the stresses within the façade elements are limited to the yield stress to ensure that there is no permanent deformation of the materials. Further, the framing members of the cladding are designed, engineered and checked to ensure that there is no buckling caused by the compression loads imposed in the axial direction (Euler Buckling), as well as, the compression loads imposed due to bending (by lateral torsional bending).

In explicit, wind causes positive and negative pressure on the surface of buildings and cladding should have ample strength and stiffness to resist this load, each in terms of the types of cladding chosen and its connections back to the structure, explains Rajendra Shah, General Manager – New Age Products, Century Ply. Cladding can help to reduce mechanical and electrical energy needs, and so enhance electricity efficiency and lower the running costs, he adds.

Choosing the Right Cladding Material: Key Factors to Consider

Cladding of any building requires engineering characteristics, should be aesthetically appealing, and should comply with visuals, says Rajan Govind, Director & Façade Specialist, BES Consultants Pvt Ltd.

Selection of material depends on factors like the architectural intent of the designer, types & properties of the product, and the loading factors at the desired location and elevation angles, adds Shabbir Kanchwala, Senior Vice President, K Raheja Corp.

In today’s context, choosing the right cladding system is essential to bringing the environmental impact of the building down in a future context as façade construction accounts for almost 35 per cent of the building costs, adds Ar. Gurpreet Shah, Principal Architect, Creative Group.  A few other factors that might be essential to the selection of materials for the cladding system should be – usage type of the building, internal and external conditions, durability, local context, planning requirements, accessibility and build ability, appearance, availability, budget, maintenance requirements as well as the structural requirements.

According to Devesh Kumar, Sr. Manager – GICS & Technical Support, Aludecor Lamination Pvt. Ltd., in addition to the above points, the key factors for selecting the material for cladding are its ability to withstand wind load and fire ratings of the product.

Factors like building height, seismic conditions and required product size to decide the type of cladding, adds Julie Etavard, Business Development Manager (in charge of the India market), Terreal.

Consideration of wind factor is important for selecting the thickness of the cladding, says Patil. Open areas decide the ventilation factor. The structural framing design of the panel is imperative for withstanding static and other dynamic structural loads. The material grade and coating decides its life span, preventing corrosion. According to Patil, the best choices are aluminium (marine grade – 5xxx series) considering the saline environment, and Stainless steel 304 grade, though they are expensive but long-lasting.

According to Keswani, the key factors to be considered while designing and selecting materials for cladding are structural performance, corrosion resistance, water tightness, air permeability, thermal resistance (by conduction/convection/ radiation), aesthetic intent and artistic finish, and reduction in carbon footprint.

Application of Cladding – Points to consider while designing and material selection:

• External and internal conditions
• Use of the building
• Resilience, strength and durability
• Fire resistance
• Planning and requirements
• Building regulation requirements
• Accessibility and buildability
• Aesthetics
• Availability & budget
• Maintenance requirements
• Structural requirements
• Control of air leakage
• Integrity and continuity of Insulation
• Prevention of water penetration or provision of drainage
• Control of thermal movement • Ease of installation
• External attachments and fixings

(Inputs by Rajendra Shah, General Manager – New Age Products, Century Ply)

Best Exterior Cladding Materials as per Indian Climatic Conditions

The Indian weather ranges from tropical in the south to temperate in the centre to Alpine climates in the North. So depending on the region, the choice of cladding materials could vary. Indian climatic conditions require any façade materials to be of external grade that could withstand harsh conditions like hot and humid weather, and also highly durable in wet and dry climates, observes Rajan Govind. The market is flooded with traditional materials (brick, stones, wood) to the most innovative ones like Corian, Hi-Macs (an acrylic solid surface), Cor-Ten steel, etc., the most common products used being wood, metal, brick, vinyl, and laminates.

According to Keswani, the most suited cladding materials are those with low emissivity which reduces heat losses by radiation. He adds that in temperate climates, the primary heat transfer method is conduction and thus, the most suited cladding materials are those with low thermal conductivity, thus we use materials such as thermally broken aluminium profiles as well as double-glazed units.

Considering Indian climatic conditions, Walinjkar explains that one needs to choose cladding having the following properties:

• Resistance to corrosion: Materials shall be having high corrosion resistance like aluminium, and steel and they should be properly treated with hot dip galvanizing and epoxy or PU paint.
• Cleaning and maintenance: We must know the cleaning cycle of the external building envelope while selecting cladding. (If cleaning cycles are not regular then we need to select material that will attract less dust and with minimum horizontal surfaces as architectural features, flush seal systems must be avoided, non-bleeding sealants need to be used for weatherproofing of system, etc.)

Walinjkar suggests glass, aluminium solid sheet, aluminium composite panels (FR grade A2), natural stones, terracotta, pressure laminates (HPL), copper cladding, zinc cladding, fibre cement board cladding, Corian cladding, GFRC etc. as best suited cladding materials.

There are varieties of cladding materials/systems used these days. It’s quite difficult to distinguish them from one another and numerous methods for installation too, says Rajendra Shah. The most suitable products are those which do not contain any hazardous substances like ash or asbestos. According to him, the best suited are fibre cement board (FCB) & fibre cement panels. However, the all-weather cladding material popularly opted in the country are engineered marble and porcelain tiles, points out Amit Shah.

Saini chooses wooden cladding and waterproof aluminium cladding as the best-suited products. Unlike traditional cladding, they both can be easily fixed in the least amount of time, is exceptionally durable, lightweight and maintenance free, and weather, moisture, and UV resistant as well as eco-friendly cladding. These materials do not rot, warp, peel or fade and are even impervious to insects, adds Saini. It is also one of the pleasant materials that neither gets too hot nor too cold, maintaining stability regardless of the external conditions. Further, stone and ceramic materials are also used in the cladding that provides an earthy effect and is also eco-friendly, helping the overall performance of the building.

Architects from Creative Group suggest terracotta cladding panels as the most suitable cladding material since they are durable, resistant, require minimal maintenance, are thermally insulated and aesthetically provide another dimension to the building. “Our highly intensive tropical climate calls for more measures towards ‘green cladding’ that will be able to add more years to the life of the building,” adds Charanjit Shah.

Julie Etavard too emphasises that terracotta cladding is compatible and excellent for Indian climate conditions. Terracotta panels have low-thermal diffusivity; it contributes to a stable and comfortable indoor temperature during the day and night. Its ventilated system allows air to circulate throughout the panels (joints are not sealed) and cool down the whole facade. Also, they are fired over 1000 degrees Celsius resulting to have fixed colours that will not fade over time and which are UV resistant. Pollution and acid rain are not damaging the products and they are maintenance-free. Clay is a natural and inert material; meaning through its natural property, it keeps the heat received during the day and releases it when it’s cooler during the night, helping to control the temperature inside, she adds.

To ensure the cladding accustoms itself to the geographical climate, products like Mangalore roofing tiles or exterior stone finish that can be sourced from the local region and is abundantly available, are the best bet, suggests Kanchwala.

HPL (High-Pressure Laminate) is the best for exterior cladding, says Kanwar, as it can be exposed to the combined action of sunlight and atmospheric agents including rain, hail or wind deposits. These are not affected by thermal shocks and have the ability to withstand extreme climate changes. Further, it reduces the amount of water that is absorbed and provides protection against chemical or air pollution.

How Cladding helps in controlling the internal environment?

The primary function of cladding is to split the indoor environment of a building from the outside in such a way that the outdoor environment will not affect the indoors. It is also best for regulating light penetration and controlling the radiation and conduction of heat from the sun and prevents interiors from getting faded and dull. Additionally, sunshades and louvred panels allow for reflected light to enter the building which enhances the comfort, rather than direct sunlight.

Gurpreet Shah emphasises that the cladding is like a thermal layer to minimise heat gain/winter frost gain. If installed correctly with proper vapour cavities and ideally using climate favouring cladding materials with adequate insulation, the thermal mass can be rightly reduced, which in turn would make the internal environment of a structure very pleasant with little or no requirement for mechanical measures to regulate the temperatures inside. Adding to this, Kanchwala points out that designs like filler slabs, double roofs, cavity walls, composite walls, and shadings also help insulate buildings.

Contrary to the above comment of Gurpreet Shah, Rajan Govind observes that for Indian climatic conditions, insulations do not necessarily add significant benefits (except in very hot regions). Insulated cladding will benefit in reducing heat loads only for very hot climates, notes Govind. Furthermore, such cladding is majorly used on walls in front of shear walls or beam/column locations. He also points out that any cladding system should be equipped with ventilated rain screen principle so that the cladding system will have an extended life and lesser risk of corrosion and damage.

A façade that is ventilated and insulated can save up to 70 per cent on energy costs for heating or cooling the building. Cladding of a building ensures that the internal temperatures are maintained at ideal levels, reducing both the cost burden of HVAC and the impact on the ecology, states Amit Shah. Another point mentioned by him is the protection from water permeation. Many parts of the country experience heavy rains and cladding serves as a coat that reduces the infiltration of water into the primary structure.

Acoustic Performance of Cladding

The acoustic performance of the cladding depends upon the substrate behind the cladding which may vary as per the thickness of the wall and constructions, says Amit Shah. Devesh Kumar adds that an insulated façade provides better sound absorption.

According to Rajendra Shah, the isolation of noise is excellently achieved with partitions that are airtight, large and resilient. The use of the resilient pad prevents the transfer of sound originating inside the structure to outdoors, vertically through the cladding members, he adds.

Deviating from the above views on the acoustical properties, Gurpreet Shah points out that cladding necessarily does not provide adequate sound insulation with the exception of brick (a high mass, high thickness system).

The level of acoustic attenuation of the cladding material is decided based on the type of external and internal environment, with respect to the frequencies and amplitude of the ambient noise and sounds. Laminated double-glazed units having varying glass thicknesses, with acoustic PVB is the best choice for acoustics, states Keswani.

Exterior Wall Cladding for better Thermal Insulation and Effective Ventilation

Facades are designed with passive and active ventilation, such as double-skinned facades that allow the warm air to rise, and exhaust from the void between the two skins, explains Keswani. Additionally, for high-rise buildings where windows cannot be opened due to high wind pressures, passive ventilators are the solution, which can be opened and closed. This allows for air circulation through the façade without the need to open the window.

The rear ventilated facade concept is quite popular and helps save energy costs while increasing the lifespan of building sustainability, spots Kanwar. He warns that poor design, detailing or installation may compromise cladding’s performance and can result in safety problems like cladding collapse or cladding panels pulling away from the structure. One should pay particular attention towards control of air leakage, thermal movement, condensation, integrity and continuity of insulation, prevention of water penetration, maintenance, resilience, etc. while selecting or designing cladding to gain effective results in both thermal insulation and effective ventilation.

The cladding assembly can control the radiation and conduction of heat. Cladding is made from a low-conductive material to stop localised condensation on interior surfaces. It eliminates thermal bridges and controls/stabilises the desired degree of the conduction of heat into and out of the building.

Prof. Charanjit Shah too states that the integration of thermal insulation with the cladding system (the most common insulation materials being mineral wood and polystyrene), forms a closed insulation envelope which helps to eliminate thermal bridges. The ventilated air gap between the primary face and the cladding face is responsible for draining the heat and moisture from outside the building and preventing it from reaching the interiors which regulates thermal insulation to the greatest extent.

Composite claddings having insulation with higher R-values (the measure of a material’s resistance to heat flow) can eliminate the need for bulk insulation between the frames in many climates. With effectively designed and efficiently mounted vapour cavities, condensation risk can be reduced or eliminated. Tensile fabric can alternatively be considered as a second cladding layer which provides a facade as well as shading to a structure.

With a selection of a better cladding system, says Walinjkar, we can achieve the desired value of thermal insulation. A wide range of products is available with low thermal conductivity (U-value). Widely used curtain wall systems can control the heat transfer from a hot external ambient temperature of 300C – 450C to an internal ambient temperature of 200C -240C by introducing the barrier of EPDM gaskets for better thermal insulation. Polyamide strips are used to cut the heat flow from either side and provide the best thermal values.

How to Achieve Desired U-Value:

• With the use of Rock wool and mineral glass wool, we can achieve very good thermal insulation on a spandrel area of the facade by increasing the overall system U-value.
• Curtain wall claddings support effective ventilation through the use of an openable vent. With advanced technology we can use active or passive ventilation in the facade, there is development in accessories for the openable vent to maintain micro ventilation. Micro ventilation keeps the room well-ventilated.
• The double skin facade provides great flexibility for the best combination of U-value and effective ventilation to remove hot air by natural or forced ventilation. The skins may be single or double kept 20cm – 100cm.

In the application, considering the cross-section of a Trombe wall, says Rajendra Shah, both the insulation values and transparency of the cladding material are of critical consideration, particularly in cooler climates where nighttime heat loss can offset the daytime heat gain. Trombe walls rely on the combined action of thermal lag of the mass and insulation from the air gap. Unwanted convection is controlled with open-able vents at the top and bottom of the wall. Additional insulation can also be gained in cooler climates through the use of double glazing (higher SHGC, lower R-value) or multi-celled polycarbonate (lower SHGC, higher R-value).

In India, one of the biggest energy consumption for buildings is its HVAC. Cladding structures ensure a significant reduction in HVAC costs while reducing the carbon footprint. A marble-clad façade can be made opaque with a set degree of opaqueness that is suited to a given environment. According to Amit Shah, this ensures that the building receives sufficient light while cutting off external noise and air pollution.

Role of Cladding in Buildings for Fire Safety

Fire safety is the set of practices intended to reduce the destruction caused by fire. Local regulations for safety norms should be followed to achieve the desired level of fire safety by the use of appropriate materials.

Cladding materials play a key role in fire safety, hence it is important to choose the right materials. In lieu of the recent fires that have devastated many buildings around the world (Grenfell Tower Fire) a shocking revelation has emerged, the use of substandard cladding panels or an improper installation of the cladding system can undermine the safety of an entire building.

Fire safety of cladding needs to be addressed at the selection stage itself and any cladding material should comply with fire retardant characteristics and relevant international standards/local standards if exists.

Sometimes, what’s meant to protect the building from external environmental discomfort might turn out to be the cause that facilitates fire, warns Ar. Gurpreet Shah. It, in turn, dissolves other firefighting measures such as fire compartmentation and phased evacuation strategies. We can avoid the loathe of such hazards by ensuring that the cladding systems that have undergone proper fire safety tests and have the highest level of insulation magnitude. Another important point on the checklist is ensuring that the cladding systems are installed properly with proper joineries and fixing details.

Fire safety strategies of curtain walling include the use of fire stops and smoke seals to limit the spread of the fire and smoke from floor to floor, points out Keswani. Conventionally, the use of GI sheets with Rockwool Insulation and fire sealants have provided a two-hour resistance. However, today, there are tested assemblies available from companies (such as Siderise and Hilti) that provide a warranty and certification for the same.

Additionally, it is also important that the cladding material should not propagate and are non-combustible so as to limit the spread of fire along the external façade. There is a risk in fire conditions that composite panels are attacked at the joints or the panels suddenly delaminate and the metal facing falls away, thus exposing the combustible core which then intensifies and spreads the fire, observes Rajendra Shah. The sudden increase in fire severity can accelerate the failure of the adjacent panels, so that if a fire does take hold, it can race up or through an entire facade of a building, causing a major hazard to occupants and a major property loss.

There is a lot of ambiguity in choosing the right materials due to consideration of inappropriate or inadequate information during procurement. Yes, overall in the industry, there is a significant shift from conventional materials to fire retardant (FR) materials, agrees Kanwar. HPL, even in the standard grade, does not burn very well, or rather, does not ignite easily when exposed to flames and contributes relatively low in the event of a full-scale fire. Flame retardant HPL is manufactured with special halogen-free additives that make it flame resistant, complying with Standard EDF-(EN 438-6 Fire Retardant). “More technically, fire resistance is the ability to retain the load bearing capacity (R), integrity (E) and insulation (I) properties for a defined period of time and it is useful to use REI properties while constructing buildings,” explains Kanwar.

The small-scale reaction test can also be done for cladding materials which provides better knowledge of the reaction of materials. It’s also very important to check the products that are used in multi-storied buildings (18m or above) and they must be of limited combustibility. Cladding  material that is rated for fire safety and fire performance, and those which normally incorporate an insulated core (such as sandwich panels), are apt for containing fire spread in a building, stress Akash Saini

Fire strategies can play a major role in the case of any fire hazards.

• Surface propagation: The reaction to fire characteristics of the materials used within the external cladding system will affect the rate of fire spread up the building envelope by way of the surface of the external cladding system. By using fire retardant materials in cladding, we can avoid huge fire hazards.
• Cavities: Cavities may be incorporated within an external cladding system, or may be formed by the delamination or differential movement of the system in a fire. And this cavity may act as an insulation chamber between the internal and external environment.
• Fire breakout: Following the initiation of a fire inside the building, if no intervention occurs, the fire may develop into a flashover and break out from the room of origin through a window opening or doorway.
• Fire re-entry: Cladding system in window and door stops fire re-entry.
• Fire service intervention

Fire Testing of External Cladding Systems

The overall fire performance of the system is reliant on the interaction of all the elements used within the cladding system, i.e., rendered insulation, ventilated cavity cladding and built-up systems.

There were various tests conducted to check the performance of cladding materials. Talking about the building codes for fire and life safety, Devesh Kumar points out that in India we have National Building Code 2016 in Chapter 4 ‘Fire and Life Safety,’ where it is mentioned to use façade with a fire rating of Class 1 in accordance to IS12777 and the material along with assembly to be tested for 2 hours. Kanchwala too agrees that, as per the Indian Standard code, the materials shall comply with the requirement of IS 1642 & IS 12777 having a flame spread index matching the requirements.

Devesh Kumar further adds that for the fire performance test for resistance to fire, first we should have a 2-hour test from ASTM E119 and then the assembly should also pass either NFPA285 or BS8414. For resistance to fire, EN13501-1 can test flame, smoke, molten droplets and heat released. The material to be used up to 15m building height should be Class B S1 D0 and above 15 m should be Class A2 S1 D0 in accordance to EN135011.

BS8414 is one particular test method that was specially developed to demonstrate under a simulated fire in a compartment breaking out of any opening in the external wall, the cladding system will not permit excessive fire spread up the building. Accordingly, each cladding material is rated for fire resistance, elaborates Keswani. However, there are certain suppliers, who provide samples for the test that differ from the material that is actually supplied to the project. Hence, one should ensure that random samples are sent to the test laboratory from each batch of material delivered to the project site.

If the materials in an external cladding cannot meet limited combustibility requirements, then it is very important to demonstrate compliance with AD B by testing the cladding as a whole and satisfying the performance criteria in BR 135 (As per the guidelines mentioned in the requirements of Building Regulations in the UK, Part B Fire Safety). It is also very important to check the installation and testing of a complete cladding system, which allows materials themselves to be combustible with meeting the requirement of BR 135 which helps in maintaining the appropriate safety standards (BR 135 Fire performance of external thermal insulation for walls of multi-storey buildings. 3rd edition BRE (2013).

There are several tests being used globally for cladding materials depending upon the regions and building regulations:

• ISO 9705 room test: Products are tested to simulate their end-use application, so products that have different end-use applications can achieve different classifications.
• The single burning item test (EN 13823) measures the spread of flame, heat release, smoke production and the extent of flaming, burning droplets.
• The small flame test EN ISO 11925-2 evaluates the ignitability of a product exposed to a small flame ignition source and measures flame distances, the burning time and any flaming droplets or particles generated.
• Large scale test
• BS 8414 -1: 2002 is the test method for non-load-bearing external cladding systems applied to the face of a building. The test determines the comparative burning characteristics of exterior wall assemblies by evaluating the characteristics:

– Fire spread over the external surface

-Fire spreads internally within the system being tested

– Mechanical response, i.e. the degree of distortion.

Source: Rajendra Shah, General Manager – New Age Products, Century Ply

Two available tests for HPL cladding materials:

• BS 476: Part 7: 1997 – Class 1 results in this test means the HPL exterior cladding used is of good quality. According to the Class 1 test result, the spreading time and extent of fire over the tested panels are very slow. While Class 4 means quick flame spreading. So HPL with class 1 results is safe to use at our homes and buildings.
• REI Property – Fire resistance is the ability to retain the load-bearing capacity (R), integrity (E) and insulation (I) properties for a defined period of time. In the construction of buildings, this is assessed for finished elements with structural functions (e.g. doors or walls) in which the HPL laminates are just one component. REI 30 or REI 60, here numbers show the time in minutes for which the HPL panels will retain their properties. So higher the numbers in REI properties, good and safer will be the HPL panels.  Stylam Industrie

Application of Cladding to Prevent Fire Spread

The new concepts, materials and ways that have emerged in the millennial world tend to put aesthetics above safety quite many times but fail to realise that aesthetics will follow the lead of safety in the long run. A properly tested, installed and maintained cladding can not only provide shelter from external factors but can also be the reason that the fire never spread to the entire structure and was uprooted at its cause itself. Therefore, the cladding material should not facilitate catching fire at the surface and in worst-case scenarios, when it does, it should phase away from the building to prevent fire from spreading to the vicinity thus, successfully preventing a disaster.

To decrease the risk of spread of fire through building facades, two options of passive fire protection could be considered, points out Kanwar – by using flame retardant treatments to improve the reaction to fire performance of the cladding material in the entire design and geometry of the façade; and by using construction elements capable to avoid the contact between the fire plume and the combustible cladding.

The first axis of the so-called passive fire protection consists of slowing down the development of a fire and its rapid spread by using construction materials with low flammability and combustibility, explains Rajendra Shah. This measure is related to the reaction to fire of materials such as wall, floor, ceiling and facade claddings as well as materials that are in the vicinity of the exposed surface.

Passive fire protection relates to the building’s structure as well as to the building’s finishing and relies on the following principles:

• 

  The use of cladding materials with good reaction-to-fire characteristics, in order to delay the development of an incipient fire.

• The realisation of compartmentation to confine the fire, for a defined period of time, to the compartment in which it started. A high fire-resistant cladding material can achieve this to an extent.
• To preserve the load-bearing function of structural elements (columns, beams, walls) during the fire, appropriate cladding material selection is important. The key points regarding fire safety are to prevent the spreading of smoke and fire in the building. Suitable fire stops and smoke seals play a crucial role in preventing the spreading of fire. Additionally, fire retardant materials are used for external cladding. There is provision for necessary openings for safe evacuation & passage of smoke. The framing which holds the cladding makes it robust and prevents the structure from collapsing during a fire spread.

How can apt cladding prevent the spread of fire in building facades?

• 

  Passive fire protection: It consists of slowing down the development of a fire and its rapid spread by using construction material with low flammability and combustibility.

• Fire and smoke stop: To stop the spreading of fire between floors, the gap between the building and the cladding system must be treated with 2hrs fire rating and sealant to stop the smoke.
• Vertical fire separation: Top stop the spread of fire between two rooms vertical fire separation is a must. The separation shall be done using fire-rated material with 2 hours fire rating.
• Cladding material: The selection of the right material plays a major role in fire safety, there are many projects where lives are lost and lots of destruction happens due to the use of wrong cladding materials. Cladding material must have Fr grade A2 class (No significant contribution to fire at any stage of the fire)

Consider the case of ETFE (ethylene tetrafluoroethylene) panels at The Water Cube Stadium in Beijing, China. In the said case, the cladding material possesses this amazing property of “self-shrinking” or melting away from the structure, thus letting the smoke out and in turn facilitating ventilation during a fire hazard. It is necessary in today’s scenario to consider materials with a low carbon footprint as well as recyclable materials. Always remember the performance in testing relates directly to real fire performance, reminds Saini. So to know how to prevent the spread of fire in building facades, do the test under the simulated whole-room fire in a compartment being emitted from an opening in the external wall, the cladding system will not permit excessive fire spread up the outside of the building.