What if you repainted your roof white? This increasingly popular practice, known as the “cool roof”, has many advantages, from cooling your home to boosting the lifespan of a roof. It could even lead to significant energy savings.

Painting the roof of a building white to reduce the heat inside sounds so simple, yet this practice is still far from systematically applied. This method is by no means new, but it’s becoming more and more popular in many countries as heatwaves become more frequent and intense.

Widely deployed in the United States, creating a cool roof essentially involves applying reflective paint – that is, 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. There’s a scientific reason for this: about 30% of energy leaks from buildings come through the 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 could make for significant energy savings. It may, for example, reduce or eliminate the need to switch on the air conditioning – something that countries with a warm climate in Southern Europe have long understood.

In Greece’s Cyclades islands, the roofs of the renowned whitewashed houses that cling to the cliffs are similarly 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 startups have begun to specialise 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 Nîmes 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 in electricity costs thanks to this technique.

But reflective paint is not the only way to practise 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.