The proof is in the roof
BY JAYASHREE MENDES
A roof is a roof is a roof is no more a byword for Indian consumers. The varied architectural solutions providing innovative shapes and attractive colours are changing the way roofs are perceived in India. Especially among urban consumers, there is a demand for better quality, technically advanced roofing systems, which in turn is driven by their purchasing abilities from the conventional roofing system.
The Indian roofing and wall-cladding industry (most of the times they go hand in hand) is poised for a sustainable growth and is preparing for the next generation of ambitious projects with equally winning products and solutions. While clay tiles and other conventional methods of roofing are passé among the well-informed consumer, the modern consumer looks for solutions that come in metal.
Roofs in India have come a long way from the traditional country roofs to the modern galvanised roofs or even the industrial roofs. According to Ranjan Dhar, vice-president and CMO, Essar Steel precoated facility, “There’s a gross shift from the traditional roof to the pre-painted roof in India. This has seen in a global increase in demand of nearly 20-25% for roofing materials like steel alone, which otherwise sees an increase of 6-8%.”
Metal roofing as a concept was introduced a few decades back to replace asbestos cement panels. The idea gained ground with the evolution of pre-engineered steel buildings for industrial manufacturing sectors. Since most structures that people inhabit are residential or commercial buildings, they go with reinforced cement concrete (RCC) roofs.
Metal roofing systems are progressively being sought by developers of commercial and public facilities. No more are building mere single structures. Based on land availability, they’re becoming complex structures. Hence, numerous styles of roofing are evolved by architects to create elevations and design. It’s a general observation that while creating these elevations, metal roofing systems offer fair flexibility to design different contours and geometrical patterns that were not easily realizable with conventional RCC/asbestos sheet roof construction systems. This has pushed fibre cement sheets deeper into the rural. The shift is largely driven by aesthetic appeal (colours), easy relatively easier installation and its state of being as non-fragile.
Abhaya Shankar, managing director, HIL Limited, says, “As per data, about 55% of the Indian market continues to use RCC, followed by clay tiles (18%).
Fibre cement sheets contribute around 11%. The segment seeing an increasing demand is metal roofing which expects to see a growth of 30% CAGR. This growth is predominantly seen in developed states, cities and rapid urbanisation.”
The entry of multinational corporate houses as well as designers has brought a positive change in traditional design practice as well as construction practices. Customers in these categories are not only demanding world class proven solutions for roofing applications but also are very particular about validation of these systems against structural and fire integrity of the buildings.
While styles and types of roofs are chosen based on country, climate, economic status, etc, a few points are important when selecting a new roof system. While cost and durability head the list, aesthetics and architectural style are looked at seriously, too.
The right roof system for a home or building is one that balances these five considerations: Roof covering, sheathing, structure, flashing and drainage. With the advent of technology there are lot of choices available for customised roofing depending on the usage. Major focus today is to use natural lighting, reduce energy cost, security and durability and of course aesthetics.
Numerous architects and developers are constantly heard saying that roofing systems are part of the first line of defence in the complete building envelope followed by walls, windows, doors etc. Roof assemblies are designed to protect the building, its content and its occupancy from hazards expected from fire, wind, weathering and other perils over many years of service life of a building. Today’s built-up environment, constructed by government as well as private developers include auditoriums, gymnasiums, sport stadia, large temperature- controlled commercial buildings like shopping malls, office spaces, exhibition halls, airports, conventional centers, just to name a few. All these buildings, based on their functional use, require basic features like thermal comfort, acoustic comfort, architectural/ aesthetic requirements, human safety (structural / fire), clean environment (indoor air quality). These features are further enhanced or complemented to minimise impact on environment and surrounding atmosphere.
Abhijeet Kale, additional general manager, technical & marketing, Lloyd Insulations, says, “Every such functional requirement impacts our examination while compiling or designing roofing assembly for each specific building envelope. Roofing is always an important part of any building affecting overall life and effectiveness of the entire building in the long term. Optimum performance of the building depends heavily upon the correct roofing system.”
The advantage of using insulated metal roofing is that these roofing assemblies can be factory finished or built at site depending upon the building roof geometry. Metal roofing has its advantages as well as disadvantages. Normal metal roofing system is very effective in terms of weather tightness till 30-3 ½0 slope. Kale adds, “If buildings call for roofs of lower slopes, one has to choose the option of non-metallic built-up roofing system finished with high efficiency weather barriers like TPO (Thermoplastic Polyolefin), PVC or EPDM membranes. We offer numerous types of metallic as well as non-metallic roofing systems which can be insulated or non-insulated combined with acoustic features like optimum internal sound absorption as well as required sound transmission class.”
Most companies make concepts that are demanded for specific end-use. Companies like Lloyd make over eight tried and tested systems consisting of built-up roofing of systems featuring pre-insulated panels with different insulation cores (PUF/PIR/Rockwool). Special built-up roofing systems for architectural applications feature external surfaces of aluminium standing seam profiles or TPO membranes.
Rising corporate and public awareness about climate change, carbon foot print, etc. has given new dimensions to initiatives like green building concepts.
Roofing industry in India is preparing for the next generation of projects, with infrastructure and industrial growth being a major demand driver for roofing and cladding. A major shift has also been witnessed from clay tiles and conventional roofing to fibre cement sheeting. The emphasis now is on a perfect blend of aesthetics, durability and superior quality.
Specialized concepts like green roofs to minimize heat island effect are also available in the Indian market. There are quite a large number of applications that are engineered and addressed with metal roofing concepts with colour coated galvanized or zinc aluminium coated metal profiles. Very special applications which invite low radius bending and special geometric contour requirements are engineered with aluminium alloy based standing seam metal profiles. Aluminium exterior can be furnished in stucco embossed self colour or PVDF colour coated finish. Applications like flat roofing where metal profile have limitations from view point of weather tightness, non-metallic outer finishes like TPO, PVC or EPDM are offered as part of roofing assemblies.
With the availability of these options, architects and designers have the choice to design any roof in any slope and in any shape. Till recently, only industrial metal profiles were available and designers could not feature them in buildings with low slopes. Kale adds, “Typical trends in Europe or America have made available assemblies providing guaranteed water tightness even in near flat roofs as long as attention is paid during detailing and installation and maintenance protocol is observed. Most of the product finishes are very effective in terms of Solar Reflective Index (SRI) which has been given high importance in green construction practice. As is well known, SRI is colour and finish specific.”
Tata BlueScope has been the torch bearer in introducing some of the advanced roofing technologies in the Indian construction sector. The LYSAGHT brand with a legacy of 150 years along with the support of the strong R&D team of BlueScope Steel, Australia, has developed innovative high quality products as per the market demands. Some of the technologically advanced steel building roofing products offered by LYSAGHT include: TILE profile that offers a pleasing appearance, similar to that of the clay tiles with the strength and durability of steel; FLEX-LOK 400 that caters to designs like geometric shapes, concave and convex structures of roofing; and SMARTDEK 51 which is proving itself as an alternative for conventional reinforcement materials, especially in high rises.
On its part, HIL offers a host of products to its customers keeping in mind rising awareness on environment conservation.
Green certified products by Griha and IGBC are finding their way in most of the constructions today. In fact the building designs are developed keeping in mind these green products. HIL has Aerocon range of products that are low on carbon foot print, energy saving and help buildings earn the crucial LEED points.
The government of India is promoting use of non-conventional energy sources like, photovoltaic solar collectors rigorously. There are special incentives offered for use of systems like PV Solar.
Currently, Lloyd Insulations is working on a few proposals wherein PV Solar Panels are integrated with almost all types of roofs. Challenges involved are integrity of the entire roof from view point of water tightness and structural integrity of PV solar panels. The company has engineered PV solar systems with its roofing applications with importance given to cost economics and track records.
In the near future, most companies expect at least 50% of the roofs in industrial, commercial and public buildings will be with PV solar systems.
Before installation of PV systems the building owner should have the roof structure analyzed by a structural engineer to determine its ability to support the system. Crystalline modules weigh about 15 kg/m2. There will be additional load of supporting structure depending on the construction practice followed. It is also important to check wind up-lift rating required for PV system and its integration with building structure. Using roof top PV will allow the building that is seeking LEED certification to achieve points in Energy and Atmosphere (EA) Credit 2, Onsite renewable Energy.
Choosing metal roofing as the platform for a PV system can also help a building acquire a point in:
Sustainable Sites (SS) Credit 7.2, Heat Island Effect: Roofs; Materials and Resources (MR) Credit 4, Recycled Content; and Credit 2, Construction Waste Management.
SS Credit 7.2 encourages use of roofing material compliant with solar reflective index (SRI) values. For a low slope roof, SRI must be greater than or equal to 78.
For a steep slope roof, SRI must be 29 or greater for 75 percent of the roof. The SRI is a unit-less value that is calculated using ASTM E 1980, Standard Practice for Calculating Solar Reflectance Index of Horizontal and Low-sloped Opaque Surfaces. It takes into account the Solar Reflectance, Thermal Emittance, and Wind Speed (e.g. Convective Cooling) to determine a value that gives an indication of the roof surface’s temperature.
The perceived complexities of choosing the right systems are outweighed by the long term benefits to building owners. As PV technology continues to improve, the decision process is also becoming easier.
Kale of Lloyd Insulations says, “Our geographical location is favourable for using solar power. There are efforts by the government to promote this energy resource through 12th Five Year Plan.
Roof top solar power generation has been given a separate status.”
States like Tamil Nadu have announced plans to generate solar power of 350MW through roof top installations.
Such schemes are also implemented for industrial areas and most of the green field projects will have roofs of solar installation either to generate electricity or hot water purpose.
The potential or opportunities for such utilization are definitely very vast. The most important part will be, to implement it effectively with safe and weather tight construction practice.