The world’s cities tend to be warmer than surrounding rural areas due to heat-absorbing concrete construction materials and a lack of natural vegetation that cools the air through shading and moisture evaporation. Architects and designers can help reduce the urban heat island effect with environmentally-friendly designs.
Penn State researchers have determined that certain urban design factors can greatly improve the ability of city surfaces to reflect sunlight and lower air temperatures.
Green Roofs and Walls
A green roof, which consists of a layer of growing medium on top of a building, can help reduce the urban heat island effect by providing shade and lowering surface temperatures. This helps to reduce energy use for air conditioning during the summer and heating in the winter, while reducing greenhouse gas emissions.
Green roofs can also absorb and sequester carbon from the atmosphere, both in the vegetation and the growing medium. The process of photosynthesis converts atmospheric CO2 into plant biomass, removing it from the air and storing it in place.
The absorbing nature of the soil and plants on green roofs can also insulate buildings against noise, such as the roar of heavy traffic. For example, an office building under the flight path of San Francisco’s International Airport was planted with a mix of grasses and wildflowers, which helped to lower noise levels by 40 decibels.
Extreme urban heat can have a number of health impacts on residents, especially those without access to air conditioning. The hottest neighborhoods often include poor communities of color that are affected by discriminatory housing practices, and they tend to have less vegetation and trees than other areas of town. Planting street trees, installing cool roofs, and using green walls are all ways to reduce the urban heat island effect in these neighborhoods, helping people lead healthier lives.
Reflective Surfaces
The urban heat island effect is the phenomenon of areas within a city that are warmer than surrounding rural areas. The cause is that buildings and roads soak up sunlight during the day, absorbing the sun’s energy. During the night, these structures release this energy back into the air as heat. This is in contrast to the natural surfaces of trees, grass and bodies of water that provide shade and cool the surrounding air.
A key factor in the formation of a heat island is the albedo of the surface. Surfaces with low albedo, like black asphalt, absorb the solar energy and produce more heat than light-colored ones. This is also why paved areas of a city are hotter than unpaved, green spaces.
As a result, the people in these areas are exposed to higher temperatures and more intense heat waves, especially as climate change makes global warming worse. It’s important to reduce the intensity of these hotspots because they make us more vulnerable to dangerous weather conditions.
To combat this issue, cities are adopting several strategies to cool the city. These include installing cool roofs, reducing the use of non-permeable pavement and increasing street trees. Cool roofs reflect the sunlight and decrease building temperatures, while cool pavements vaporize moisture to reduce surface temperature. Both of these technologies help lower urban temperatures and improve occupant comfort.
Energy-Efficient Technologies
Energy efficiency, or energy efficiency technology, involves minimizing the use of resources to provide goods and services. Energy-efficient technologies include insulation, double glazing, low-emissivity windows, LED lighting and other lighting options, solar photovoltaic systems and good old-fashioned electricity conservation (such as reducing or eliminating unnecessary idling of cars).
Local governments can take a number of different approaches to promoting energy efficiency, including improving the efficiency of their own operations and facilities through product procurement criteria, encouraging the adoption of green practices by citizens and promoting energy and climate policies in their communities. Energy costs can be a significant line item in municipal budgets, so improving energy efficiency in buildings, homes and businesses can result in substantial energy cost savings, while demonstrating environmental leadership and enhancing sustainability.
Cities with dense concentrations of impervious surfaces – such as asphalt roads, parking lots and rooftops – are especially vulnerable to the urban heat island effect. Research shows that these areas typically have higher temperatures than surrounding areas, which can lead to increased energy consumption for air conditioning and increased health-related problems like respiratory illnesses, strokes and heart attacks. Additionally, the urban heat island effect can disproportionately impact poor communities due to historic redlining policies that systematically deprived many of them of access to natural resources and cooler spaces. To mitigate the impact of the urban heat island effect, cities should look to implement strategies like shade trees, painting building facades lighter and repaving asphalt roads with cool materials.
Sustainable Urban Development
As climate change and urbanization continue to reshape the world, sustainable development practices are becoming increasingly important. These practices focus on creating a more environmentally friendly city by reducing energy consumption, waste and pollution while maximizing economic growth and social connections.
Cities can reduce the intensity of heat islands by increasing vegetation, introducing reflective roofs and pavements, and developing innovative road and sidewalk designs. They can also utilize sustainable materials, such as light-colored paint, phase-change materials, fluorescence paint and more, which are thermally efficient, have a lower environmental impact and require less energy to produce than traditional building materials.
Furthermore, they can adopt smart zoning practices to vary the height of new buildings and promote more walking and public transportation, which will help reduce air pollution and car traffic. Finally, they can invest in sustainable infrastructure, such as water and wind turbines, solar panels and more.
In addition, they can implement strategies to support historically disadvantaged neighborhoods, as they are more likely to experience higher temperatures than other areas within a city. These residents also often have pre-existing health conditions, like asthma, that make them more vulnerable to extreme heat. Additionally, these communities may have fewer resources to invest in cooling or heat-reduction measures. To address these issues, it is vital to invest in sustainable development practices, such as providing affordable access to cooling and energy efficiency technologies, education and community engagement.