Preventing Urban Heat Islands

On a hot sunny day, the sun heats dry, exposed surfaces. In shady or wet areas, this effect is drastically reduced. In urban areas where the most surface area is roofing, asphalt, and concrete, temperatures can be 60° hotter than the air. Not only does this mean that you should watch your skin and watch out for your pet’s skin when outside, but these temps raise the surrounding heat as well.

Heat islands contribute to higher daytime temperatures in urban and suburban areas, which has a whole gamut of negative effects.

  • Higher energy costs. When it’s hotter in cities, more people use air conditioners. If you’ve ever been near an AC unit’s exhaust, you know how much hotter that makes the outside. This results in a negative feedback cycle of people making the atmosphere warmer in order to stay cooler inside. It also puts a higher stress on the power grid. Heat waves in Europe and the US kill people when the power goes and people can no longer use AC or fans.
  • More greenhouse emissions. With higher electricity use comes more greenhouse emissions. This also contributes to the negative feedback loop. People use more electricity to stay cool, thus more greenhouse gas is produced, which exacerbates the greenhouse effect. This heats up the entire globe slowly but surely. Not to mention the negative effects of impaired air quality on peoples’ health and well-being.
  • Extreme heat is bad for human, animal, and plant health. As we mentioned earlier, extreme heat waves have been a reason for many deaths in the US. When the local environment is negatively affected by the heat, plants and animals die off. As shade trees and the animals that help support and propagate them die, the negative feedback loop continues.
  • Worse water quality. Warming bodies of water can not support ecosystems as well. Marshlands and other wetlands play a huge role in filtering and cleaning water of contaminants. Even a few degrees increase in temperature of a body of water can kill off the animals and plants living in it. We are already seeing this effect with coral reefs throughout the ocean.

What causes heat islands?

The main culprit here is paving. Asphalt and asphalt paving gets much hotter than other materials. Partly, the black color of asphalt absorbs more light and thus produces more heat. Partly paving can simply withstand more heat than other sources. Paving is a poor conductor of heat, so when it finally does get hot, it retains that heat for some time, and it’s difficult to dissipate.

The most commonly-used asphalt and paving materials can reach summer heat of 120°-150° F.

How to reduce heat islands and their effects?

Green parking lots

As asphalt is one of the main reasons for heat islands, parking lots are one of the worst offenders. These huge, black, paved areas simply absorb and radiate heat. Fortunately, a good solution is to use more environmentally friendly parking lots. Green parking lots are essentially a pavement grid with growing plants between the pavement. Obviously reducing the paved surface area helps mitigate heat islands, but there are other benefits too.

  • Better water drainage. The plants growing between the paving (usually grass) will suck up rain and runoff water.
  • Cost-effective. It’s often cheaper to put some pavement in the soil than completely pave a new area.
  • Easy to repair. Replacing some parts of concrete is much easier than doing a full asphalt paving replacement.

Light colored concrete/roofing

White pavement and roofing reflects more light than it absorbs. This helps to keep the surfaces, and thus the surrounding air cool. In fact, one part of climate change is that the polar ice caps bright whiteness reflected a lot of the sun’s light back out of the atmosphere. As they melt, the darker ground absorbs the light and thus builds more heat. We can mimic the ice caps reflectivity in urban areas.

Green roofing

Growing plants on rooftops rather than using shingles made with asphalt has many benefits.

  • Less heat absorption. Green areas are less hot than pavement in the sun.
  • Benefits the local ecology. Often, the plants grown on rooftops are low maintenance and natural to the area. This means that they can support local pollinators and other wildlife. Additionally, natural plants that may be pushed out by invasive species in some locations can have a chance to thrive.
  • Water absorption. This reduces runoff and helps to improve water quality.
  • Plants cool the surrounding areas and act as insulators. Thus, they reduce high-power demands such as air conditioning.

Cool pavement

Cool pavement is a relatively new technology that shows a lot of promise. Of course, the easiest way to cool pavement is to paint it a light color, as we mentioned before. However, there are more advanced ways to lessen pavement’s heat impact in development. Different technologies can be used to make pavement more reflective rather than just a lighter color. Of course, it has some hurdles too. Pavement exists primarily to be walked and driven on. This means the reflective coating will eventually wear off as well as get covered in black marks from vehicle tires. Nonetheless, cool paving is still a great way to go to reduce the urban heat island effect.

Want to pave to reduce heat?

Looking for a paving contractor who is environmentally aware? At Reliable Paving, the vast majority of our asphalt is already recycled. We also keep up to date with the most recent developments and innovations in the industry. If you want to resurface your parking lot, build a driveway, or get something paved while beating the heat, then give us a call today.