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 technology is by no means new, but it’s growing more and more popular in many nations as heat waves get more regular and extreme.
Widely deployed in places of hot temperature, creating a cool roof essentially involves applying reflective paint, i.e. white paint that reflects the sun’s rays towards the sky.
The Albedo Effect
The phenomenon known as the “albedo effect” causes the roof to absorb less heat, keeping the building cooler.
And with good reason—building roofs account for almost 30% of all energy leakage from structures.
●These white paint coatings also aid in the preservation of the roof by shielding it from any overheating damage.
●Because a cool roof can result in large energy savings, it also has a significant ecological impact.
●For instance, it may lessen or completely do away with the necessity to turn on the air conditioning!
●Furthermore, Southern European nations with warm climates have long recognized this.
The Art of Cool Roofing
Similarly painted white are the roofs of the famous whitewashed houses that perch on the cliffs on Greece’s Cyclades islands.
According to green roofing specialist Geoff Smith of the University of Technology Sydney, who was quoted by The Guardian, a white roof reflects over 85% of the sunlight that touches it. When the temperature gets close to 40°C, this significantly drops it.
If you’re concerned about the high mercury levels that are being reported, you can take a simple action that will help cool down both your home and the entire city: paint the outside of your home or office building white, or cover it with white HDPE or PVC sheets or tiles. They are referred to as “cool roofs.”
The science behind it
The roofs of buildings, which are primarily constructed of concrete or, in the case of low-income housing, other materials like asbestos and galvanized metal, collect solar radiation from the sun.
The sun’s heat that is absorbed by the roof then builds up within the house. It will not heat up as much as it would normally if building roofs are coated with materials that can reflect the bulk of solar radiation.
Reflectance is the capacity of a substance to reflect solar radiation. Even thermal emittance has a significant impact. The energy that a material absorbs can be released by it.
The Solar Reflectance Index (SRI), which measures a material’s optimal mix of solar reflectance and thermal emittance, is used to choose the best material to cover the roof.
The ideal materials for a cool roof are those with a high SRI, such as white cement tile, white paint, and white PVC sheets, according to statistics from the Bureau of Energy Efficiency.
White PVC sheet and white paint have SRIs of 100, whereas white cement tile has an SRI of 90, making it more durable.
Role of Urbanization
Rapid urbanization causes open spaces in cities, such as lakes, forests, and agricultural areas, to disappear and be replaced by man-made buildings constructed primarily of concrete or other heat-absorbing materials like metal or bitumen. Cities or urban conglomerates are hence heat islands since they are significantly hotter than their suburbs.
Conclusion
The UHI impact can be lessened, though, if many buildings begin to have cool roofs. This will also reduce the quantity of heat absorbed in the city. Cool roofs are another strategy recommended by the US Environmental Protection Agency for reducing the UHI effect.