Do you live in or near a heat island, and is there anything you can do about it?
The answer to the second question is yes.
So what is the answer to the first question? What is a heat island? Usually it refers to an “urban heat island.” Check the diagram. It’s when cities get warmer than their surrounding suburban or rural areas. Summer is the big show for heat islands.
Unshaded roads, parking lots or buildings can gain heat from the sun and heat up the air around them. Highly developed urban areas may have mid-afternoon temperatures 15°F to 20°F warmer than surrounding, vegetated areas.
Aside from temperatures, do urban heat islands matter?
Yes. Higher temperatures with urban heat islands hit people several ways (Source):
- Health: Heat islands can intensify extreme hot weather, which can cause breathing problems, heat cramps, and heat stroke, and may lead to illness or even death – especially in vulnerable populations such as the elderly.
- Air Quality: Heat islands raise energy demand to power air conditioning, which in turn can increase utility bills and increase power plant emissions of carbon pollution that causes climate change. Higher temperatures also accelerate the chemical reaction that produces ground-level ozone, or smog.
- Water Quality: Hot pavements heat up stormwater runoff, which can hurt aquatic life in local waterways.
- Energy Use: Heat islands are responsible for 5 – 10 percent of summertime electricity demand, leading to higher electricity bills, pressure on the electricity grid, and brownouts and blackouts.
This seems so relevant to the Carolinas. After all, isn’t at least one city known as “Famously Hot” already?
Researchers say that heat wave related deaths could quadruple by 2050. “Globally, heat is the number one weather-related killer, causing more deaths each year than floods, tornadoes, or hurricanes. Extreme heat can kill directly via heat stroke and indirectly through increased risk of heart attack and stroke. Climate models show that in some cities the number of high-heat days could double by 2040.” (Source)
It all seems way bigger than one energy consumer. We get it. Let’s break it down, starting at the city level. Here are some large-scale mitigation strategies (Source):
- Trees and Vegetation – Increasing tree and vegetation cover lowers surface and air temperatures by providing shade and cooling through evapotranspiration. Trees and vegetation can also reduce stormwater runoff and protect against erosion.
- Green Roofs – Growing a vegetative layer (plants, shrubs, grasses, and/or trees) on a rooftop reduces temperatures of the roof surface and the surrounding air and improves stormwater management.
- Cool Roofs – Installing a cool roof – one made of materials or coatings that significantly reflect sunlight and heat away from a building – reduces roof temperatures, increases the comfort of occupants, and lowers energy demand.
- Cool Pavements – Using paving materials on sidewalks, parking lots, and streets that remain cooler than conventional pavements (by reflecting more solar energy and enhancing water evaporation) can cool the pavement surface and surrounding air.
- Smart Growth – These practices cover a range of development and conservation strategies that help protect the natural environment and at the same time make our communities more attractive, economically stronger, and more livable.
How can one electric customer make a difference in heat islands?
Start with “Neighborhood Solutions,” as described by a magazine, UrbanLand. “Heat resilience efforts are also resulting in an increased focus on neighborhood-level heat solutions. Philadelphia is leading this approach with the publication of the city’s first Community Heat Relief Plan … [the Hunting Park neighborhood had] 9 percent tree coverage and a land cover of 85 percent buildings and hardscape — compared with 9 percent and 51 percent citywide averages, respectively — Hunting Park is one of Philadelphia’s hottest neighborhoods.”
That is a clue: Know where the hottest parts of a city are, and why.
How about individual homeowners? Here are a few ideas.
Green walls. Great idea if you want a garden on your wall, especially when you have little yard. “Somewhat like a shade tree, a living wall system can shade the sides of a home or other building that get direct sun,” says the City of Austin, TX. (Image, left and below) “In this way, it can reduce energy use and costs – especially when installed on an east or west facing exterior wall. Living walls typically require installation on a manufactured system. The plants receive water and nutrients from the vertical support system, instead of the ground. Some systems allow intricate garden designs – with vines, flowering perennials, foliage plants, and even food production.”
Permeable pavements. Reflective pavements have been tested with various results. Permeable pavements may offer more creativity. Think of your driveway, for instance. Is it a hot expanse of pavement? “Also called pervious or porous pavements, permeable pavements are designed to allow water to pass through pores between rocks. … As water passes through the pavement, some of it adheres to the pavement and eventually evaporates. Because water requires heat from the surrounding air to transform from its liquid phase to vapor, permeable pavements can cool the surface and surrounding air as water evaporates from pavement system.” (Source)
“Permeable Interlocking Concrete Pavers (PICP) are a type of cool pavement that reduces runoff, promotes cooling through reflection of sunlight and the movement of air permitting evaporation to occur around paver materials.” Check more on that from a resource of the City of Gilbert, AZ.
Trees. An easy on for people with yards. Says American Forest Association, “Properly selected and planted trees provide shade to buildings and sidewalks, helping to reduce temperatures. Trees provide additional cooling through transpiration—a natural air-cooling effect that occurs when trees release moisture into the air. This is especially beneficial in places where heat is trapped in concrete and asphalt surfaces. And because cool air naturally settles near the ground, temperatures directly under trees can be 20 to 45 degrees cooler than air temperatures in nearby unshaded areas.” In addition to heat, tress filter the air.
Why mention heat islands in winter? Because people will be out in a few months working on their homes and yards. Plan ahead.
As an energy consumer the message is to get involved. Homeowners can add trees, green walls, or change pavements (as long as the HOA says OK). As citizens, get involved with city efforts to reduce heat islands. If your city doesn’t have that kind of effort, help start it.