How to cool off a city
I’d often go for a walk in the neighborhood before we hit the triple digits. I got to see a single family house built, or, rather, rebuilt not far from our home. It was a first rate job. With one exception. I couldn’t figure why the builders covered the roof in black, asphalt tile. Sure, it looked nice contrasted with the white walls of the house, but heat? That house’s roof became a heat island.
During my walks, I have also noticed a reduction of large trees in our area. Trees don’t live forever so occasional replacement is required. Whether it’s the higher cost of water, the increase of rentals rather than owner occupied houses, or ignorance, trees are being cut down but not replaced. Trees are the first choice of those who want to reduce heat in an area and beautify it.
One doesn’t need to live in the Valley very long to realize the importance of shade and reflective colors. The people I know who work outdoors in the heat wear long sleeve, neutral color shirts. Super sizing this concept to the city level is not as big a leap as you might think.
Last week, the PBS NewsHour ran a segment on what the City of Phoenix is doing to cool down a growing urban area, population 4.7 million, that’s in the middle of the Sonoran Desert. Government entities are responsible for public safety so treating escalating heat as a natural disaster, the city created “Heat Ready.” The city alerts residents about dangerous heat levels and offers emergency cooling centers.
A second program, “Nature’s Cooling System,” is redesigning low-income neighborhoods to alleviate some of the worst heat. Volunteers wear temperature gauges and UV monitors in vulnerable parts of the city to measure where heat is most intense. Plus, locals’ experiences are shared with public officials. The outcome might be to add drip irrigation for trees and drinking fountains near bus stops.
The city has also created a Heat Response Office headed by a “heat czar” who interacts with the homeless and other residents checking on people’s health during heat emergencies. Other organizations are involved particularly in redesigning poorer, hotter neighborhoods. These include The Nature Conservancy, Arizona State University, and the Maricopa County Department of Public Health. Not surprisingly, one of their first defenses against heat is trees.
To this end, a couple of non-governmental organizations are leading the effort to plant more city trees. One of these organizations is Trees Matter, and I’ve been receiving their newsletter for a couple of years. Their strategies transfer to small cities such as those we have in the Valley. Trees Matter draws many of its volunteers from Arizona State University. Trees are often planted at schools. The students assist in digging the hole and irrigating learning about the benefits of trees and the importance of their care.
Another strategy for city cooling, and one more the purview of public works, is creating cooler surfaces. Phoenix is experimenting with coating black asphalt roads with a reflective film. This coating lowers the street surface substantially. Other strategies include using light colored permeable surfaces that allow rain water to seep through and create trans-evaporation.
Of course each approach costs money, but so do existing measures or lack thereof. I recall nationwide weatherization measures launched by community service organizations in the 1960s. But this was to protect low-income homes against the cold. The same is needed, albeit decades late, for structures in hot areas particularly as more cities experience the effects of global warming.
Ideas are not lacking. Public awareness, political foresight, and community innovation are. Phoenix is certainly a
U.S. leader on cooling cities. And other countries, especially Australia, provide successful examples on reducing urban heat. Passive solar architecture, urban forests, water elements designed to cool, reflective roofs and roads, and wide use of native vegetation are common solutions.
You can plant a tree in the fall when it’s cooler, and in the meantime install sun shades. Call IID and ask what programs it offers. Stay hydrated and keep cool.