How white roofs can help buildings beat the heat

In Greece's Cyclades, the roofs of the famous whitewashed houses that cling to the cliffs also have a white finish. Photo: AFP Oia, Santorini, Greece - AUGUST 26, 2015: Man stays on the white roof of hotel and paints it with big swab and speaking mobile phone.

Paint the roof of a building white to reduce the heat inside. It sounds so simple, yet this practice is still far from systematically applied.

Known as a cool roof, this method is by no means new, but it's becoming more and more popular in many countries as heat waves become more frequent and intense.

Widely deployed in the United States, creating a cool roof essentially involves applying reflective paint, i.e. white paint that reflects the sun's rays back towards the sky.

Thanks to this so-called "albedo effect", the roof absorbs less heat, which helps keep the building cooler. And for good reason: about 30% of energy leaks from buildings come from their roofs.

These white paint coatings also help to preserve the roof, protecting it from damage potentially caused by overheating. A cool roof also has a significant ecological impact, since it can make for significant energy savings. It can, for example, reduce or eliminate the need to switch on the air conditioning! And this is something that countries with a warm climate in Southern Europe have long understood.

In Greece's Cyclades islands, the roofs of the famous whitewashed houses that cling to the cliffs are also rendered in white. According to green roofing expert Geoff Smith of the University of Technology Sydney, quoted by The Guardian, a white roof reflects about 85% of the sunlight that hits it. This significantly reduces the heat when the mercury gets close to 40°C.

The cool roof technique is also gaining momentum in France. A few start-ups have specialised exclusively in the sale of reflective paints, such as Cool Roof or Energycool. And the method isn't only of interest to households. A Carrefour store located in the southern city of Nimes has applied a white coating under its solar panels installed on the roof.

Similarly, the E.Leclerc store located in Quimper, Brittany, claims to have saved €20,000 (RM90,519) in electricity costs thanks to this technique.

But reflective paint is not the only way to practice cool roofing. A green roof produces similar effects in terms of thermal insulation, since plants create a kind of protective screen against the sun's rays. – AFP Relaxnews