Zinc is truly an international metal. It was used in ancient times in Greece and Egypt and during the Middle Ages was produced in the form of metal in China and India. Zinc also played a dominant role, in the building of modern Paris under the influence of Baron. In fact parts of Asia and Europe in particular have used zinc as a building envelope material for generations. In US, the recent growth in its use is based on the recognition of the green and sustainability attributes that it can provide to a building design. The use of zinc as an architectural metal of choice is gaining popularity in India also and is catching up with its widespread and long term use in other parts of the world. For example, VMZINC is the international brand name of rolled titanium zinc products manufactured and sold by the building products unit of the Umicore group. In India though the group was present for past 13 years, its building products business started in 2010 only. As per Girish Dharachar, General Manager, Umicore India Pvt Ltd, “Our titanium zinc based roofing and facade solutions have now been used in almost 40 building projects that are at various stages of execution across the country. Some of the projects have facades as large as 10,000 m2. In addition, the product which is basically used for cladding & roofing of buildings is of late being used in interiors also.”
Zinc for architecture
Although zinc is a relative newcomer to the Indian construction market, it is enjoying incredible growth, as architects and builders are beginning to discover the exceptional qualities of the product as a building material.
• Resistance –Zinc is not corrosion sensitive and can be used in all climates. A self-protective coating forms on its surface when it comes into contact with the atmosphere. As these products require no special maintenance, they have an estimated lifespan of between 40 and 100 years depending on the environment. These lasting products enhance historic monuments and contemporary projects alike.
• Adaptability – It is suitable for all types of buildings. They can be installed on shallow pitch roofs from 5% to vertical. They are designed to meet specific local requirements, current regulations and can be used in new and renovated buildings.
• Integration -The malleability and elegance of these products are a source of architectural freedom of expression that is both diverse and rich. They can be used for classic and complex forms (conical, single or double curves) and adapt perfectly to dimensional constraints (on or off site forming and discreet finishing details).
Dharachar explains, “The life of titanium zinc is expected to be more than 100 years. The metal is 100% recyclable and sustainable. If one is to compare the metal to other materials used in the building industry, it requires far less power to manufacture; so it consumes lesser natural resources. In India, aluminium is very commonly used for facade and roofing applications in different product forms like composite panels or solid sheets and usually uses a silicon sealant for water
tightness. But there is maintenance associated with such products. In contrast, as zinc is very malleable, usage of sealants is avoided. Since, it can bend easily; “Flashings” are used that cover and overlap corners providing with a fantastic finish. All of single skin Titanium Zinc façade applications are dry joint systems. They are dry clad; it means that there are no sealants and flashings are used for all the corners, widows joints etc. The advantage is that the buildings remain practically maintenance free. Titanium Zinc can also be soldered very easily thereby achieving excellent detailing & finishes.”
Zinc offers distinct aesthetics for innovative building purposes. If you seek a pre-weathered look for a project, the pre-weathering process provides the look of aged zinc with the bonus of being maintenance- free. Alternatively, coloured zinc allows architects and home owners to create colourful designs with an expanded palette that blends perfectly with other materials.
Natural zinc is shiny silvery in colour. When the metal is exposed to the exterior environment, because of atmospheric impurities and moisture, the zinc reacts with the moisture in the atmosphere and forms zinc hydroxide that reacts with carbon dioxide to form zinc hydro carbonate. This process is called Patination which is a two stage process and prevents any further reaction of the environment with the zinc. This layer of the zinc hydro carbonate is fairly non porous and it protects the zinc underneath. In places like Mumbai, Chennai, Mangalore patination will happen very fast, but in places like Khandala, Darjeeling, Coorg it will take a longer time for the process to get completed. The zinc looks non homogeneous until the entire process is completed and uniform appearance is achieved once patination is complete
Moreover, Zinc availability in several colours makes it possible to use it in many different ways and mix it with other materials. Combined with wood, concrete, brick or glass, the six different surface aspects can play on contrasts, create relief or simply be used in harmonious combinations. Maintenance-free zinc colour finish will not peel or crack and will fade to a natural gray over a 30 to 50 year timeframe. An excellent alternative to copper and painted aluminium, coloured zinc uses modern pigment technology and showcases the naturally grained texture of pre-weathered zinc. The surface colours range from organic red, green, blue and brown pre-weathered zincs.
In addition, to achieve faster patination and a homogeneous looking surface, factory pre weathering is done. For instance VMZINC pre weathered zinc with a chemically treated upper layer is available as:
• Quarter-Zinc®, featuring the same appearance when new as preweathered natural zinc,
• Anthra-Zinc anthracite grey in colour that blends well with slate and
• Pigmento® (red, green, blue, brown) which has a subtle combination of colour and the natural texture of Quarter-Zinc®.