Turning down urban heat
Cities are hot. Machinery, cars, buildings—they all spew heat. Even the average human contributes—producing about as much heat as a 60-watt light bulb.
All that warmth adds up. In any good-sized city, downtown temperatures are as much as seven degrees hotter than the surrounding countryside. And all the buildings and roads create a massive heat stockpile that radiates for hours after the sun sets.
Scientists say cities are heat islands and that's where David Sailor associate professor of mechanical engineering, steps in.
Sailor (pictured at right on The Broadway's green roof) studies how much heat is gained or lost by specific activities or items—say, driving to work versus staying home with the air conditioner on. Or planting 100,000 trees versus installing 1,000 green roofs.
Sailor hopes his data will help people understand how to turn the urban heat island's temperature down. And it has.
Until Sailor's research, architects and builders could not evaluate precisely whether a green roof would benefit their project. Did a layer of soil and plants allow a building to absorb less heat and therefore use less air conditioning? Using software developed by Sailor, they can now figure it out.
Sailor is also part of a PSU faculty team mapping Portland and Houston, Texas, block-by-block to determine the precise air temperature coming from asphalt roads and from shady lanes. When he's done, cities will be able to verify whether planting 100,000 trees, for example, will really pay off in lower temperatures.
The project is also surveying residents to determine what they actually do when they hear an air quality alert, which will help governments determine how best to design effective advisory systems.
For Sailor, cooling off the island all starts with the data. "Understanding the causes of the urban heat island," he says, "is the first step in knowing what to change."