News
Barcelona tests three paints to reduce heat in buildings
This summer, Barcelona will try out a solution that seems simple but could improve comfort inside buildings: painting rooftops with materials that reflect more solar radiation and absorb less heat. The experiment will begin in Les Corts, on the roof of Institut Escola Tres Fonts.
The aim is to see whether certain types of paint can lower indoor temperatures without changing the traditional look of Barcelona’s rooftops. The idea isn’t to cover everything in white, but to find solutions that cool without disrupting the city’s usual appearance.
The test will compare three different finishes: a white paint, a conventional terracotta, and a terracotta with reflective pigments. The latter is one of the most interesting options, as it aims to keep the characteristic colour of many rooftops while improving their performance in the sun.
The problem is becoming more obvious. In summer, rooftops are exposed to hours of sunlight and can become a source of heat that transfers into homes, schools, and facilities. In poorly insulated or badly ventilated buildings, this build-up makes it harder to rest and increases the need for cooling.
The experiment also aims to measure whether these paints help reduce energy consumption. If a rooftop heats up less, the building needs less air conditioning to stay at a comfortable temperature—important in a city where heatwaves are more frequent and tropical nights leave less time to recover.
The test will also take place at the Vibrantz Technologies facilities, using two identical cabins painted with conventional terracotta and reflective terracotta. Both will have air conditioning limited to 27 degrees, allowing a comparison of electricity use and checking whether the innovative paint reduces cooling demand.
Technicians will also analyse the potential of radiative cooling, a passive process that allows some surfaces to release heat to the outside, especially during clear nights. This mechanism could be key for buildings to not only heat up less during the day, but also lose heat more easily at night.
Monitoring will be done with sensors measuring temperature, humidity, solar irradiance, and electricity use. The aim is to have real data before deciding whether these solutions can be extended to more rooftops, schools, facilities, or urban renovations.
The initiative is part of the city’s strategy to adapt Barcelona to extreme heat. The Pla Calor includes measures to reduce the heat island effect, improve thermal comfort, and protect the population in a dense city with lots of asphalt and buildings not always designed for such harsh summers.
In neighbourhoods like Les Corts, the experiment may seem small, but it raises an important question: how to make buildings more liveable without major works and without driving up energy costs. Painting a rooftop won’t solve climate change on its own, but it could be another step in the city’s everyday adaptation.
Barcelona is looking for solutions that go beyond big plans on paper. If the results work, rooftops could become allies against the heat: discreet surfaces, visible from above, but crucial for making homes, schools, or facilities more comfortable when the temperature rises.