• Jane Marsh.
    Jane Marsh.

CCN contributor, Jane Marsh, explains how solar reflective coatings could help reduce the impact of the Urban Heat Island Effect.

Rapid urbanization has seen vegetation replaced with non-reflective construction materials for walls, roofs and pavements.

As a result, cities are steadily becoming warmer, with far-reaching health and financial implications. Solar-reflective coatings have emerged as a promising solution to combat rising temperatures and save lives.

Summers are notorious for being extremely hot and humid, but they are even more so in cities and urban areas with more concrete structures than trees.

Without adequate natural land cover, buildings, roads, and other infrastructure quickly absorb and reemit solar heat, resulting in higher temperatures.

Several cities are already experiencing more frequent hotter days. For instance, in New South Wales — where nearly 90 per cent of the population lives in metropolitan areas — average temperatures can be 1° Celsius to 3° Celsius hotter than in rural environments.

Everyday activities like electricity usage and transportation that generate heat exacerbate the situation.

With this increase in city temperatures, the demand for cooling across residential and commercial buildings has risen, leading to higher energy costs. Urban overheating also poses significant health risks. Research indicates a 1˚ C temperature rise corresponds to a 2.1 per cent increased risk of heart disease. 

Today’s cities have an abundance of darker surfaces that absorb more sun heat, from black asphalt roads to coloured rooftops. While beautiful to look at, these elements increase urban heating. During midday, the surface temperature of concrete and asphalt can get up to 25 degrees Celsius higher than that of grass. 

Solar-reflective coatings contain heat and UV-light resistance properties. They act as a barrier to prevent heat absorption and reduce surface temperatures. Recent advancements in this technology have resulted in discussions around the possibility of employing these solutions on a city-wide scale.

Recently, Purdue University researchers unveiled a reflective paint containing barium sulfate nanoparticles, allowing the coating to per cent of sunlight. It can also cool outdoor surfaces below ambient temperature and reduce indoor air-cooling needs by up to 40 per cent.

Plans are underway to use the paint for rooftops to address the effects of urban heat islands, but that is only the beginning. Vehicles, building walls, pavements and other integral city infrastructure could also benefit from the reflective, cooling properties of the coating.

Rather than wait for new constructions to apply heat-resistant coatings in buildings, city planners must look into using it on existing structures.

This approach can accelerate the city’s efforts to reach its climate change goals and create a more comfortable living environment. Repurposing and retrofitting a building can be done in 18 per cent less time and for about 16 per cent less than new constructions.

In 2022, scientists at UNSW Sydney conducted a cost-benefit analysis of implementing coated roofing systems across major Australian cities. The study found adopting such a solution in Sydney could lower cooling energy consumption by up to 40 per cent in residential and commercial buildings. That translates into significant cost savings.

Reduced air conditioning across an entire city is a step in the right direction for sustainability. Less electricity usage means decreased reliance on fossil fuels and lower greenhouse gas emissions.

2023 was the warmest year since record-keeping officially began in the mid-1800s, with global surface temperatures rising  1.18˚ Celsius higher than the 20th-century average.

Australians recently endured their third-hottest summer ever since 1994. Without active steps to stem the increasing rate of warming, 2024 could be on course to set a new record.

The need for innovative cooling solutions and climate mitigation methods has never been more dire, especially with urbanization set to ramp up over the coming years.

Lighter, reflective surfaces can dramatically minimize solar heat absorption and emission in cities. Now is the time to take action toward tackling urban heating before it becomes too widespread and uncontrollable.