Cover Story

Look out for the materials and methods to make Façades more efficient, safe, useful and aesthetic

October 2017
Between the environment exterior to a building and the interior environment lies the Façade. 'The first and most important function of the Façade is to act as a filter between the inside and outside environment,' says Manit Rastogi, Founder Partner, Morphogenesis. 'The Façade modulates daylight, heat gain, glare and solar control. Also, it is expected to fulfil structural performance expectations, in terms of wind load, structural integrity, etc.'

Performance over aesthetics
Performance is the buzzword in Façades nowadays. 'Functionality, utility and longevity are our clients' top priority although they want a material that is simultaneously strong on aesthetics,' says Ankit Mohata, Managing Director, Straton Group.

'From a functional point of view, owing to poor civil construction, cladding is becoming a necessity. Also, in terms of energy-efficient Façades, cladding is here to stay,' says Dr Prashanth Reddy, Managing Director, FunderMax India (Read his full interview on Pg 50).

Typically, the energy load of a Façade should not exceed 1 W per sq ft, reckons Rastogi. However, he opines that most Façades are very inefficient, presenting a load of 4-5 W per sq ft.

Fatade performance is critical in a hot and dry climate or composite climate. While performance also matters in a hot and humid climate like Kolkata, the intensity there decreases slightly, says Rastogi, decreasing further in a city with a more temperate climate like Bengaluru. Having said that, climate change has increased the overall temperatures that the latter city experiences.

To enhance the performance of a Façade, control the window-to-wall ratio and use high-performance glass, suggests Rastogi. Essentially, think of optimising the entire building envelope, not just the Façade. After all, the elevation or the Façade is not separate to a building but an integral building element.

'Fatade performance depends on the kind of building you make and the context you are designing in,' says Sanjay Puri, Founder, Sanjay Puri Architects. 'A Façade is not designed in isolation and stuck onto the building; it is integrated with the building.' Puri cites an example: A building in a warm climate, say in Rajasthan, should be north-oriented with hardly any sun coming in from the south, to reduce heat gain by 30 per cent. Accordingly the north side should have larger openings compared to the south side.

'Max Exterior panel from FunderMax - used in conjunction with rear ventilated Façade - is eco-friendly and can help achieve the necessary energy-efficient rating,' says Dr Reddy. 'The manner in which the panels are installed and the way they perform result in thermal efficiency along with product characteristic.'

High-pressure laminates, wood-polymer composite and other cladding fitted with rear ventilation slightly lower the interior temperature and can thereby reduce the energy load of a building, says Mohata. 'Essentially, the ventilation ensures air circulation and insulation. While some of these Façades can cost up to two-and-a half times the cost of ordinary panels, discerning developers are increasingly favouring a higher capex against lower opex in the long run.'

Culturally aesthetic Façades A Façade can make or break the look of a building, and hence attract or put off potential clients and tenants. 'Aesthetics are important because finally people live in the space and expect it to look good,' says Harshavardhan Neotia, Chairman, Ambuja Neotia Group. However, aesthetics as applied to a Façade are about more than meeting the occupants' expectations. 'A building should ideally blend in with the culture of the place; this goes for the Façade as well,' he adds.

'A Façade is not only important from the perspective of performance of the material, a deep understanding of the cultural heritage of an area is important to design buildings that look familiar, to enmesh the cultural connect of people, place and climate,' says Sharukh Mistry, Founder Partner, Mistry Architects. 'Some Façades you see today in smaller towns in India are incongruent with the culture and lifestyles of people.'

Material accountability
All the material components of the Façade are answerable for the long term, which means the materials must add rather than take away from the life of the building. If the material for a Façade is chosen on this basis, building safety will follow. Accountability also reflects in the recyclable quotient of materials; their toxicity level during and at the end of their life-cycle, points out Mistry.

'I like to use a lot of natural materials because the kind of work we do does not need high-rise; from stone and mud to newer materials like copper and steel, we combine materials in a manner that is circumspect, meaningful and ties into some element of a local connection.'

Popular materials
Today, world-class products with solutions are available, notes Dr Reddy, making a good understanding of the product at the project conception stage itself important. 'It can go a long way in helping to bring out our knowledge and services into the project and create sustainable products.'

Among modern materials, aluminium is the best and most popular Façade material, says Rajeev Antony, Managing Director, Schueco India. 'Stone or ACP cladding are other materials.

Steel is comparatively heavy and typically used as a structural material as an alternative to concrete, when it becomes the substructure for the Façade.' 'The Façade design or material must meet the aesthetic requirement of the architect, and the aesthetic appeal of the owner,' says Navin Keswani, Managing Director, Aluplex India.

'Aluminium is the preferred raw material for the profile and structural support of the Façade system; the Façade system duly designed and engineered correctly is then leak-proof, waterproof and resistant to high wind loads and adverse weather conditions. Glass is the most popular infill material for being available in a variety of colours, and permutations and combinations with respect to solar control and low-emissivity factors, for requiring zero maintenance, for its aesthetic appeal, longevity and energy-saving potential, and for ensuring the comfort level of occupants. ACP can be combined with glass to introduce a different element in the Façade.'

'Solid metallic sheet cladding is replacing ACP cladding in various applications for being maintenance-free, more fire-resistant and creating an impeccable external wall,' says Ravindra Shekokar, General Manager-Operations, TeamFacades. 'Also, architectural metal mesh is becoming popular for being suitable for a wide range of designs (perforations), especially where ventilation and aesthetics are critical.' 'New elements like clay tile cladding, sunscreen and sunshades are being used in extreme sunlight conditions,' says Kapil Chikodi, Head-Business Development, Glass Wall Systems. 'We are also using metal cladding.'

'Non-conventional, green-certified cladding with appropriate test reports and lab certificates is in demand,' says Mohata.

Glass Façades
A few decades ago, glass Façades gained popularity in the Middle East and thereafter started trending in the Indian building design scene, says Kishore Bhatija, Managing Director, K Raheja Corp.

'We are seeing good demand for glass Façades; in particular, unitised glazing systems, previously used in commercial buildings, are now being installed in residential projects in Mumbai, probably because of the new building norms or FSI rules,' affirms Chikodi.

Essentially, Bhatija says clients prefer glass Façades as they make interiors brighter, reduce the need for electric lighting, and evoke a feel-good factor in occupants. Also, energy-efficient glass is a suitable front for green buildings whose performance must be addressed through their Façade. 'Selecting appropriate glass and using it correctly can help create modern, environmentally sustainable buildings,' says Kailash Chandra Jain, President, HNG Float Glass. In the case of Façades, he explains that this involves combining high-performance glass selected on the basis of a sun-path analysis and clear float glass in insulated units, which can reduce heat transfer by 50 per cent, solar energy transmission by 40 per cent and UV radiation by over 60 per cent, leading to a 24-27 per cent drop in the building's energy consumption. Glass is additionally aesthetically appealing, fast to construct and enhances indoor comfort.

Using glazing with an aluminium system installed as a curtain wall for the Façade helps reduce the building's energy load by 20-35 per cent compared to masonry walls of concrete or brick, according to Chikodi.

Select the glass type after considering the building orientation, shading devices and percentage of glass used in the Façade, and calculating the payback time through a building simulation process, recommends Vikram Khanna, COO-Consumer Glass, COO-Architectural Institutional Business, CMO, CIO, Asahi India Glass. That said, despite the advantages, given India's hot climate 'there is a need to balance the use of glass with other materials,' says Bhatija. 'Another aspect from the design perspective is that all glass buildings tend to look the same, and we need to get more innovative.'

'Using an excess amount of glass brings in an unwanted amount of heat and light,' observes Dr Reddy. 'Also, if you have a closed Façade system with energy devices like air-conditioners working inside, it results in energy loss.' He advocates 'working with a smart design element where we can talk about double-skin Façades, we could bring in the necessary light but not the heat and prevent energy loss from the inside to outside.'

Double screens
Double-screen Façades have become popular overseas, says Antony. The two skins or screens serve the important function of providing occupants with higher building performance (thermal, acoustics and ventilation). Also, the outer skin provides design flexibility to architects for better aesthetics.

'With a dual-screen Façade, depending on the weather condition, you can disengage the openable to allow natural ventilation between the two skins, thereby creating a thermal bridge which creates an acceptable indoor temperature during summer and winter' explains Antony.

'Between the two screens, service levels and ducts can be created for the sake of convenience, and HVAC equipment placed.'

The cost factor
Fatade materials vary significantly in cost and performance. Glass Façades are more expensive than aluminium Façades in terms of the material cost, system profiles and installation, says Khanna. 'But this higher capex converts into lower opex and safety, considering fire-resistant glass can resist fire up to 120 minutes.'

'A metal Façade can be 20-30 per cent more expensive than glass and aluminium Façades owing to higher cost of solid metals,' says Shekokar.

A positive is that the industry is gradually evolving towards judging materials for their performance.

'The industry is slowly moving from being extremely price-sensitive to a value and benefits-driven approach influenced by growing awareness and global trends, which is a positive development indeed,' sums up Dr Reddy.

'Also, the industry is bracing up for the challenges of complex Façade design and so far has been able to handle it well.

The Indian Façade and cladding industry is catching up with the best of the world's architecture in some of the Façades we have seen in recent years.'

Fatade safety
In June 2017, London's Grenfell Tower went up in flames killing 80 residents. About a year prior to this disaster, the building had been given a new look, a Façade comprising two layers of aluminium sandwiching a combustible core of polyethylene, a highly flammable material. When a malfunctioning fridge triggered a fire, this very highly flammable material is believed to have helped it to spread rapidly. Questions have arisen in the UK over the need to disallow flammable cladding in Façades. Does the material used in the Façade impact building safety so majorly? What is the role of installation in ensuring the safety of a Façade and, hence, of the building? Citing the Grenfell Tower fire as well as a couple of residential towers in Dubai where fires have recently broken out, Mohata emphasises on the need for cladding material with fire retardancy and flammability-spread specifications matching ASTM or EU standards. 'Fire in a high-rise spreads mainly through the exterior cladding material, not through the RCC; so, gauge a material based on the flammability spread, toxicity report, smoke density and other parameters.'

'Fire retarding cladding is preferable,' agrees Neotia. 'Using combustible material in a Façade is as potentially hazardous as poor installation from the stability point of view,' says Antony. 'If smoke seals between floors are not done properly or as per norms, the smoke and fire can easily spread into the next floor and the whole building can easily go up in flames.'

The Façade and overall building design are critical for safety. According to Antony, the pertinent questions to ask are: How will the building react in an emergency? How many openable and evacuation points have been provided? How fast will the rescue teams be able to reach occupants?

Safety is as much of an execution as a design issue, underlines Rastogi. 'A lot depends on how the material is installed and whether the right fire stops are provided.' And that ultimately is the bottom line everyone must consider for any functional Façade - full stop.

Easy-to-maintain Façades
'Natural materials like granite are more expensive compared to regular brick walls as well as challenging to use for tall structures. Glass and aluminium are cost-effective and easier to maintain; they require regular cleaning but are durable,' says Kishore Bhatija, Managing Director, K Raheja Corp.

'FunderMax has always laid emphasis on sustainability and all our products are maintenance-free. Contrary to aluminium panels and glass that require a high element of cleaning and maintenance, our panels can be more or less classified as zero-maintenance,' says Dr Prashanth Reddy, Managing Director, FunderMax India.

- Charu Cahri
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