Why should you make your roof white?

Arabia Weather - With the intense heat waves hitting most of the northern regions of the globe during this period, and the rising temperatures and increasing humidity, it has become necessary for scientists to seek to find effective ways to reduce average temperatures for the present and the future.

A study recently published in the scientific journal Geophysical Research Letters reported that roofs painted white or reflective are more effective than roofs covered with vegetation or solar panels in reducing the temperature inside cities. Cities in general suffer from significantly higher temperatures compared to the surrounding rural areas, due to the decrease in green spaces and intense human activities in them, which increases energy consumption, polluting emissions, and deaths related to extreme heat, and these areas are known as “urban heat islands.”

Live study in London

The study in the British capital concluded that cool roofs could lower city temperatures by an average of 1.2 degrees Celsius, significantly outperforming all other factors. Although vegetated roofs are beneficial for aspects such as stormwater management and biodiversity, their effect on temperature reduction was as small as 0.3°C.

It is worth noting that the spread of air conditioning devices in London has led to an increase in temperatures by 0.15 degrees Celsius on average, which increases the complexity of managing thermal distribution within the city and reaching the optimal solution, and reflects the situation in many cities around the world.

The phenomenon and ancient knowledge

Humans have known for a long time that light surfaces reflect light, unlike dark surfaces that absorb light and heat. This phenomenon is known as “reflectivity” or “albedo.” For example, snowy and icy surfaces reflect most of the sunlight, while paved asphalt roads absorb most of the light and get hot quickly.

This phenomenon depends on the nature of the material itself. White paint consists of chemicals that do not react with any color of the visible light spectrum, while asphalt or black pigments absorb all colors, making them more colorful.

Given the effectiveness of white paint or light colors on building roofs, some researchers suggest painting all parts of the building, not just the roof. Others have suggested painting roads and footpaths white, but this proposal has been met with disapproval because of the possibility of them getting dirty quickly and the annoying glare they may cause.

The outlook on the Arab world

In comparison with the aforementioned study, many Arab cities resemble the British capital in their population density, and the impact of some solutions may be more evident there. For example, air conditioners are widespread, and they are one of the causes of high average temperatures.

The study urges taking these factors into consideration within long-term strategic plans, given the continued migration from rural to urban areas and the increase in heat waves that have become longer and stronger due to climate change.

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