The roofing industry is undergoing a sea change with the changing needs of the Indian market, growing number of applications and the increasing awareness of the consumer. Roofing systems that were earlier restricted to conventional RCC, GI or asbestos-cement sheet roofing has been revolutionized with the arrival of materials like metal, fiberglass and asphalt roofing along with improved quality of hardware, clip-on systems, fixings and trimmings that allow speedy installation with the least on-site time. Metal panels are becoming de rigueur because of their neat application and durability while solar roofing and green rooftops are gaining popularity for their inherent benefits of reducing energy costs, increasing the life cycle of the roof, and effective insulation.Architect Rupam Dey says, “Among others, one of the popular roofing systems worldwide these days is the membrane roofing. Such as, the new synthetic rubber membrane roof products which come in sheets and in liquid form that are easy to install and provide tight waterproof and weather resistant roof. Or the high tech plastic membrane roofing that is extremely strong, water tight and fire resistant and much favoured in the construction industry.”
Undoubtedly, roofing industry is evolving, providing variety of options and technologies and offering flexibility to design long-span roofs, roofs with interesting shapes or any other variation. Also with growing environmental awareness, the emphasis now is shifting on aspects like reduced carbon footprint, thermal insulation, recyclability and sustainability. The same is evident in some of the emerging roofing technologies that involve use of innovative materials and production process to offer energy management and control, ease of maintenance and superior performance.
One such roof covering is SPF (spray polyurethane foam) roofing which has been around for quite some time. However, with growing market demand for durable, long-lasting roofing systems that combine high energy performance with low maintenance costs, SPF is witnessing a renewed interest by professionals. It consists of an application of specifically designed foam, covered with an elastomeric coating (typically acrylic, silicone, or polyurethane) or aggregate covering to protect the foam from ultraviolet rays. The seamless and monolithic nature of the sprayed foam provides a fool proof method of sealing cracks and rendering any surface moisture resistance and draught proof. The closed cell foam has a low water vapour transmission properties and also inhibits ingress of moisture. In addition, the excellent adhesion of the sprayed material makes mechanical fastening redundant. The low density of the materials adds little weight to overall loading.
The firm bonding to the substrate can also add significantly to reducing vibration of thin membrane roofs and the structural strength of a building itself. Abhijeet P Kale, General Manager, Sales and Marketing Lloyd Insulations India Limited explains, “The spray applied rigid polyurethane foam is designed to combine highly efficient thermal insulation with great ease of application. Far from being confined to flat surface, spray applied LLOYDFOAM can be used for curved corrugated and irregular surfaces too. When applied on roof, the insulation effect of the foam reduces thermal movement of the roof deck and helps prevent failure of the roof covering. Although the foam forms a weather resistant membrane, a final coating is required as an additional protection against UV radiation. As of now SPF is mostly being used in industrial buildings or roofs that are inaccessible.”
As a matter of fact, SPF roofing in many ways fulfils the criteria of a sustainable roof covering as this system greatly reduces tear-offs in re-roofing projects thereby decreasing the amount of materials entering the waste stream, does not contain any ozone-depleting chemicals and the energy-saving characteristics can save considerable amounts of fossil fuel and CO2 production.
Alternatively an innovative system, NightSky, manufactured by Integrated Comfort, Inc., USA, provides temperature conditioning roofing system that exchanges thermal energy to the space through convection and radiation. Water sprayed onto the building roof at night is chilled by the night air which is drained to a storage tank. The tank water circulates through tubing in the slab floor before entering the chiller. Passive cooling delivery from the slab not only cools the building but in parallel, the “active” chilled water fan coils reduces load on building air-conditioning system.
Energy-saving benefits offered by the system include increased efficiency due to night-roof spray cooling, reduced energy use and elimination of unnecessary latent cooling. These factors help substantially to reduce peak electricity demand. Mahesh B, Founder and Managing Director at McD Built Environment Research Laboratory Pvt Ltd (McD BERL), explaining the NightSky system says, “As the roof has the largest exposure to the sky dome, it can be used effectively for night sky radiation. In the case of a building, if we expose the water on the terrace, it gets cooled because the temperature of the night sky is much less than the temperature of the water. Thus, the cooled body is the building and the heat sink is the sky, since the sky temperature is lower than the temperatures of most objects on the earth.”
In addition to NightSky technology, McD BERL offers a similar innovation which is structural slab radiant cooling roofing system. Herein water tubes are placed in the roof slab that absorbs the heat from the roof surface and exchanges it with the circulating water. The warm water is then pumped to a chiller or a geothermal heat exchanger, re-cooled and returned to the slab.