Glass and aluminium composite panel facades are making inroads across India.
Glazing has evolved exponentially in the past few years to become an integral part of projects. ´Today, India demands around 160,000 mt of glass per month, of which over half is clear float glass,´ says Vikram Khanna, COO, Consumer Glass & Architectural Institutional Business, CMO, CIO, Asahi India Glass.
Use by region and building type
Demand for glass is concentrated in the metros and Tier-I and Tier-II cities. ´While metros and Tier-I cities enjoy a healthy market for all kinds of glass, Tier-II cities are witnessing steady growth in demand for float glass including high-performance glass,´ shares Khanna.
´By region, southern, western and northern India use more glass than eastern India,´says Rajiv Balaggan, Sales Head-Architectural Glass India, Pilkington Glass India. ´Demand is growing in Tier-II and Tier-III cities.´
In his view, commercial buildings use more glass facades than residential ones. ´Hotels, showrooms, shopping malls and museums are increasingly using glass or high-performance energy saving glass,´ he adds.
Single vs double glazing
A common myth is that double glazing makes sense only in cold climates. But, Indian developers are growing aware of the use of insulated glass units. Nowadays, more commercial buildings and some residential buildings are using insulated and double glazing for improved thermal insulation and sound insulation - depending on the glass combinations chosen, says Balaggan.
´We have used insulated glass units for our projects Devagiri Divine, Temple Bells, Saketh Hill Side, Silicon Pride and Aditya Harmony,´ reveals Kashinath B, Director, 5 Elements Realty, Bengaluru. ´For the best performance of the unit - in terms of U-value and solar heat gain coefficient- we carefully scrutinise the properties of each layer of glass and appropriately determine the width of the cavity, seal type and content of the cavities between the glass layers.´
For their part, architects are spearheading innovative uses of double-glazed units. Glazing facades have their own appeal but glass should be used judiciously and intelligently, depending on the site, building orientation, climate, etc,´reasons Reza Kabul, Director, ARK Reza Kabul Architects. ´To enhance the´green´ quotient of a building with a glass facade, we have tilted the glass to an optimum angle. We have also sandwiched photovoltaic cells between the two layers of double-glazing units, by which sufficient energy is generated for lighting up car parks and common areas like the lobby, corridors, etc.´
´Low-emissivity coated-glass applications have also increased a lot for better thermal insulation´ says Balaggan. ´We prefer low e-coated glass for containing the transmission of heat and light,´ adds Kabul. ´It does cost 30-40 per cent more than normal glass, so clients sometimes need encouragement to spend extra.ö In fact, low e-coated glass variants can be hard-coated for use as single glazing with comparable outcomes to a double-glazed unit with clear float glass. Such single glazing in clear, neutral and different colour shades is commercially more viable, therefore especially preferred for residential buildings. It can even be used in commercial buildings for the IT industry.
Clear glass is the popular choice of the Indian construction industry as it is versatile, says Khanna. It can be used for windows, railings, doors, partitions, displays, and much more.
Demand is growing for high-performance clear, neutral or light-shaded glass fatades while reducing for blue or green-shaded high-performance glass,´ points out Balaggan. ´Soothing shades of glass combine low glare with high-performance, energy-saving properties.´
Structural glazing is gaining interest among architects and developers for being easy-to-use and lending itself to a variety of designs, according to Khanna. Indian companies mostly use two kinds of structural glazing for facades with floor-to-floor glass panels: Vision glazing and spandrel glazing. ´While the vision panel caters to the visibility needs of occupants, the darker shaded spandrel panels hide the floor plates,´ he explains.
An advanced option for more ambitious designers is ceramic-fritted panels. ´By fritting, glass is infused in white or colored ceramic to create certain patterns or designs or art,´ Khanna tells us.´Fritted panels can be used as spandrel glazing and, if the fritting is minimal, also as vision glazing, offering some privacy.´From the performance angle, fritted glass diffuses natural light into space, thereby reducing glare and direct solar heat gain.
Glass is one of the key sustainable materials indicated in the GRIHA, IGBC and LEED guidelines. Green buildings rated by GRIHA, IGBC and LEED use high-performance glazing as an energy-saving measure, both to cut spending on air-conditioning machinery and operational costs on air-conditioning and artificial lighting. In fact, glass is being used for facades on an unprecedented scale to create remarkable designs and yield eco-savings. ´Glass panel façade systems offer versatile, high-performance coverage,´ says Khanna. ´With the Central Government mandating that new government buildings should meet ECBC standards, the use of glass is poised to grow.´ Indeed.
Cost-effective aluminium composite panels
´India´s aluminium composite panels (ACP) market is about 25 million sq m per annum, valued at about Rs 2,000 crore,ö says Vijay Mittal, Managing Director, Wonder Aluboard.
ACPs are user-friendly and lightweight, therefore essentially used as cladding for the external facade of commercial projects; albeit, they can also be used for interior applications, observes Indrajit Kembhavi, Kembhavi Architecture Foundation. Most ACP applications are for exterior cladding - for which a variety of solid and metallic colours as well as different patterns like wood, stone, etc, are preferred,´
agrees Mittal. ´The same finishes are also available as interior partitions.´
So, why are ACPs a hot favourite for exterior cladding?
´ACP compares favourably to a marble or granite facade because it is cost-effective both to install - stone can cost 25-200 per cent more - and maintain,´ explains Mittal. ´Also, ACP weighs about 10 times less than stone, and so bears less load upon the structure.´
Further, ACPs enjoy a long life. They are termite-proof, waterproof, reusable and offer a flat surface finish. ´ACPs complement glazing; they are pliable - they can be cut, bent and folded - and are fast to install,´ adds Kembhavi. ´We have used ACPs extensively wherever it suited the architectural language.´
Choose the right glazing
Choosing appropriate glazing from the vast variety available is vital for the project´s success - it impacts energy consumption, aesthetics, safety, and more. Here are a few pointers to help you choose well: Levels of transparency: ´Choose from clear to opaque glass depending on the level of visual privacy required and the extent to which you aim to connect the exterior space with the interior or connect occupant´s biorhythms with the time of the day´ says Indrajit Kembhavi, Kembhavi Architecture Foundation. ´Visual comfort like natural light and exterior views enhance occupant´s well-being and positively impacts productivity in office buildings,´ says Vikram Khanna, COO, Consumer Glass & Architectural Institutional Business, CMO, CIO, Asahi India Glass.
Performance: Higher-performance glass offer better control of the levels of light and heat entering a space and can optimise thermal comfort, says Kembhavi. Buildings in different climate zones will need different kinds of energy-saving glass and glazing, says Rajiv Balaggan, Sales Head-Architectural Glass India, Pilkington Glass India. Glazing for a hot climate will be different from glazing for dry, cold and humid climates.
Strength: Conventional glass is breakable while toughened glass and laminated glass offer better security and can take human weight, says Kembhavi. ´Buildings facing high wind or with big panel sizes need laminated glass units mainly for safety purposes and good sound insulation,´ opines Balaggan.
Layers of glazing: Choose between single and double glazing depending on the need for light and acoustic transmission. Consider introducing special gases and louvers between two layers to optimise light and acoustic transmission, shares Kembhavi. A good fit? Last, but not least, consider whether glazing is a good fit for the project. Glazing should be used sensitively based on the sun path and climatic zone of the context, says Kembhavi. ´As a rule of thumb, in the semi-tropical climate prevailing over most of India, thermally, the northern and eastern directions are glazing-friendly whereas the southern and western directions are unfriendly.´