The urban heat island effect occurs in cities, where structures like buildings, roads, and parking lots made from materials such as concrete, steel, and asphalt cover the ground. In contrast to rural areas, where plants facilitate cooling through photosynthesis, the human-made structures in urban areas absorb and re-emit heat, making the surrounding air warmer.
Urban air temperatures can reach up to 7 degrees hotter than neighboring rural areas due to the heat island effect. And it’s likely to increase with growing urban density. Blazing heat isn’t only uncomfortable— it can also be a health hazard. In the U.S. alone, an average of 702 people die from heat-related illnesses each year. Others may suffer from ailments like dehydration, heat stroke, and exhaustion.
What can homeowners do to help? Take some measures at home to reduce your contribution to the urban heat island effect. Here are some changes you can make to help regulate the temperature of your home when the sun is beating down — you’ll also reduce your energy costs.
Start Gardening and Planting Trees
Introducing more greenery into your yard is an aesthetically pleasing way to stifle the heat. Trees and plants use transpiration to lower their temperatures. They release water vapor from small pores in their leaves, which cools them down. The plants’ lowered temperatures affect the surrounding air, which is partly why rural areas are less likely to experience the heat island effect.
Trees also provide plenty of shade when situated in the right spots, such as the east and west sides of your home. Try planting some near paved areas too, like your driveway or patio. The best trees for fending off heat are deciduous, tall, and have wide canopies to provide extra shade.
Try Greener Roofing
One easy way your roof can help combat the heat island effect in your neighborhood is to opt for lighter colors next time you need a new roof. Dark-colored roofs absorb more heat while lighter ones reflect it.
Consider your home’s roofing material, too. Green roof policies are a growing trend and for good reason. A vegetative layer on the roof reduces the roof’s temperature and can help moderate the heat island effect. Although they generally cost more than a conventional roof initially, green roofs typically last longer. And they have additional benefits including filtering water runoff and absorbing carbon dioxide.
The Environmental Protection Agency also recommends cool roofs to help reduce heat islands. These roofs reflect sunlight away from a building, thereby reducing heat absorption for a cooler house with less energy consumed for air conditioning. Though cool roofs may reduce some desired heat gain during cold weather, this “tends to be less than the unwanted energy reflected in the summer,” according to an EPA report. In general, cool roofs save energy over time.
Choose Window Treatments
Window treatments are a quick fix for homeowners looking to regulate sunlight. Heavy drapes keep sunlight out during the hotter parts of the day, and you can install shutters as exterior window treatments.
There are more advanced solutions, too. Rolling shutters give you privacy and cooler interiors, and you can operate them from inside the house. However, they also block out all light, which you may not want if you only need to reduce the heat. Retractable awnings also work well, though you may choose a slatted version to preserve outside visibility. Insulated cellular shades do double duty by reducing heat gain when it’s hot outside and preventing heat loss in the winter, while still allowing filtered light to enter.
Do you prefer plenty of sunlight? Try reflective window films that reflect sunlight away from your home. You may also decide to scrap the entire pane and install new ENERGY STAR-rated windows. Consider high-performance window glazing to improve your home’s energy efficiency. And low-emissivity (low-E) windows use a metallic oxide coating to reduce the heat entering your home, allowing you to keep the curtains pulled back without working up a sweat.
Install Attic Ventilation
The attic is a prime spot for warmth to gather. Insulating and ventilating this space can decrease the warm air buildup and help you control temperatures in your home.
Insulation regulates temperatures by slowing the flow of conductive heat. Every type of insulation reduces heat by a certain degree — referred to as its R-value — and the type you install will depend on your climate and HVAC system.
Creating more ventilation will involve installing vents or fans within your attic. Exhaust vents on the roof and intake vents on the soffits use static ventilation to generate airflow and lessen the heat. Fans can be set to operate under certain temperatures, and many are solar-powered, which saves on energy costs.
Purchase Efficient Appliances
Your appliances can stir up a lot of heat without you realizing it. The stove is the obvious culprit in many homes, but the dishwasher, dryer, and even washing machine can contribute to high temperatures. Dirty refrigerator coils mean your fridge must exert more effort to run, increasing energy consumption and heat output. Inspecting and cleaning the coils lessens the heat your refrigerator outputs.
ENERGY STAR appliances reduce power consumption, which can naturally reduce heat production, too. A new oven or fridge may be necessary for making indoor temperatures bearable. If your budget doesn’t allow for new appliances, try scheduling your usage before sunrise or after sunset to avoid heat buildup.
Your Home Can Reduce the Urban Heat Island Effect
When sunlight and heat build up in homes, the urban heat island effect becomes stronger. Strategically placed plants, reduced energy consumption, and careful sunlight management can go a long way in keeping your house and your neighborhood cool.
Individual actions can compound into significant change. Who knows — your actions may inspire your neighbors to do the same. If everyone has an energy-efficient house, everyone benefits.
Beat the summer heat by trying these stay-cool hacks.
Originally published on March 6, 2020, this article was updated in July 2023.
About the Author
Holly Welles is a home improvement writer and the editor of The Estate Update. Her work on environmental design has been published in Today’s Homeowner, Build Magazine, and other industry publications.