the alternatives to asphalt that Spanish cities already use

With the temperatures skyrocketing and the Aemet warning of new heat waves Above 40 degrees in much of Spain, it is clear that, beyond active cooling solutions such as fans and air conditioners, cities must also plan to implement urban solutions that dissipate heat in buildings and streets.

In this article we wanted to highlight one of the measures that we have been using for decades. It is a type of pavement that effectively reduces the temperature of the streets thanks to its porosity. But it is not the only type of pavement that fulfills the mission of reducing temperatures (nor the only remedy that cities have). Below these lines we tell you the details.

The thing is about pavements. There are two large families of “cold pavements”. The first are the permeable or porous pavements. These are surfaces with holes connected to each other that allow rainwater to pass into the ground instead of diverting it directly to the sewers. This retained water evaporates little by little and cools the environment, in addition to reducing flash floods.

The second family are reflective pavements or high solar reflectance (also known as “cool pavements”), which do not seek to filter water, but rather return a greater part of the solar radiation they receive to the atmosphere, instead of absorbing and storing it as conventional black asphalt does.

A type of porous pavement. Image: Pavipor

Heat trapped in the streets. Dark asphalt and concrete absorb much of the sun’s radiation during the day and slowly release it at night, preventing cities from cooling even when the sun goes down. This phenomenon, known as urban heat islandcauses large cities to register noticeably higher temperatures than in rural areas, especially at night. And of course, with episodes of extreme heat becoming more frequent, any measure that lowers the street temperature by a few degrees already helps a lot.

Examples. The most recent case is that of Barcelona. The City Council, with technical support from the Polytechnic University of Catalonia (UPC), approved last year a new reflective agglomerate on a section of Martí i Franquès street, in the Les Corts district, directly comparing it with a section of conventional black asphalt to measure the real temperature difference between both materials. As explained by the City Council itself, this pavement has the capacity to reflect a greater part of solar radiation than traditional asphalt, which helps reduce both surface heating and the temperature of the environment.

Barcelona installing a type of reflective pavement. Image: Barcelona City Council

The test is part of the municipal Climate Plan, and is not the first of its kind, since according to collect El Diario, before testing with the pavement, Barcelona had already launched a pilot plan to paint the roofs of several buildings white and with reflective pigments, including a school in the Les Corts district.

Seville, one of the cities hardest hit by heat waves in Spain, has also proposed similar solutions. And in recent years, the City Council has been adding to its planning the massive planting of shade trees, replacement of dark pavements with lighter materials in various parts of the city, awnings on commercial streets, sustainable drainage and a network of “climate shelters” distributed throughout the neighborhoods to give respite to the population during heat peaks.

These types of measures are increasingly applied on Spanish streets, especially in those large cities in the country that become an oven when summer arrives.

It doesn’t work the same everywhere. A recent study by the University of Granada, has analyzed the thermal behavior of the eight Andalusian capitals and has come to the conclusion that there is no single solution to cool a city. According to the project researchers, in Seville and Malaga the factor that weighs the most is the albedo of the materials, that is, their ability to reflect solar radiation, while in Córdoba the building density and the waterproofing of the soil have more influence, and in Granada the key is in the urban geometry and how open the streets are to the sky.

The same study also recalls that dense canopy trees continue to be, by themselves, one of the most effective tools, since they can lower the temperature between 3 and 5 degrees in parks where it is well designed. It is clear that reflective or porous pavement helps, but they work more as a complement to other urban solutions.

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