Innovative for Climate
7. Cool roofing
7.COOL ROOFING
Twenty-first century cities will have white rooftops
Repainting roofs reflective white significantly lowers the temperature inside buildings during heatwaves. This is known as the “cool roofing” principle, a cost-saving and environmentally friendly alternative to air-conditioning that is rapidly being adopted around the world. Arkema has contributed a value-added layer to this solution with Kynar Aquatec® acrylic PVDF latex, which enhances the performance and durability of white roofs.
Black absorbs thermal radiation and white reflects it. In these times of record high temperatures, this well-known phenomenon is attracting growing attention. A major innovation is spreading across rooftops from the United States to Europe and Asia and contributing to energy efficiency around the world: cool roofing. This involves painting roofs with a reflective white paint that keeps buildings cool while the temperature soars outside, and reduces the need for air-conditioning and its associated greenhouse gas emissions. New York City is pioneering this solution and already has more than 850,000 sqm of painted white roofs, following a municipal campaign launched in 2010. Meanwhile, in Europe, over the past five years an increasing number of public buildings and large retail spaces are turning white on top. The trend is being encouraged by local authorities, including the City of Paris, which has identified cool roofing in its Climate Energy Plan as a way of combating urban heat islands.
UP TO 30% ENERGY SAVINGS
In France, Cool Roof is one of the companies driving uptake of this solution. Founded in 2015, the Brittany-based start-up took on its first contract the same year, to cover 7,000 sqm of a Leclerc shopping mall. Data collected on site has recorded a 15% reduction in the build-ing’s energy consumption, representing nearly four metric tons of CO2 equivalent per year, and annual energy savings of €20,000 for the retailer. Some fifty clients have followed suit, from the 2G terminal of Paris-Roissy Charles de Gaulle Airport to the Paris Fire Brigade’s center in Villeneuve-Saint-Georges. In 2018, the Géant Casino store in Valence-Sud acquired the largest reflective roof in France, covering 18,000 sqm. The hypermarket recorded temperature reductions of up to 36°C on the roof after treatment. “Depending on the building, the reduced need for air-conditioning can represent 30% of the energy cost,” explains Antoine Horellou, Chairman and CEO of Cool Roof France. “And for non-air-conditioned spaces, we improve interior comfort.”
ARKEMA IS WORKING ACTIVELY TO PROMOTE THE BENEFITS OF COOL ROOFING.
KYNAR AQUATEC®, BOOSTING PERFORMANCE AND DURABILITY
To obtain these results, a quality coating is essential. Cool Roof – like Aximum, another supplier of reflective paints – drew on Arkema’s expertise to develop their solution. The white, highly reflective, water-based paint is protected with a UV- and mold-resistant finish based on Kynar Aquatec® PVDF. This acrylic, waterproof emulsion significantly improves the performance of white roofs by increasing reflectivity of the sun’s rays to 95%, compared with 70% for a traditional paint. Furthermore, it ensures an unrivaled lifespan. “Infrared and ultraviolet light from the sun eventually break down basic white paint. This means the roof needs repainting frequently, which quickly becomes expensive,” says Bertrand Dinelli, an Arkema cool roofing expert. The Kynar Aquatec® topcoat prevents soiling. “It’s like the difference between regular cloth and waxed canvas. The rain naturally washes away de posits and grime that would otherwise blacken the roof and reduce its reflective qualities.” Cool Roof France promises its formula will last at least 20 years.