VOA慢速英语 2008 1020a
时间：2019-01-11 作者：英语课 分类：VOA慢速英语2008（十）月
Green roofs are designed to save energy and capture rainwater. Rooftops covered with plants help keep buildings cool. They can extend the life of a roof. And they can reduce water runoff into streets and storm water systems.
Chicago City Hall
Several years ago, the mayor of Chicago, Illinois, visited Germany, a leader in green roof design. Mayor Richard Daley later decided 1 to have vegetation planted on Chicago City Hall. Today, the tops of many other buildings also look like parks.
In Canada, the Coast Plaza 2 Hotel in Vancouver has a forest on its roof.
Experts say green roofs usually do not get much above twenty-seven degrees Celsius 3. So temperatures might not be a problem for growing. But rooftop gardeners have to be careful not to put too much weight on the roof. This is true whether plants are grown in soil or water.
New York City has an unusual demonstration 4 farm for hydroponics. The farm is on a boat called the Science Barge 5. Rainwater and purified river water are used to grow lettuce 6, tomatoes, cucumbers and peppers. The farm shows the possibilities for designing rooftop systems.
Earlier this year, researchers in Texas reported that green roofs can reduce a building's air conditioning costs by about one-fifth compared to black-top roofs. But they also reported that not all green roofs perform equally well. They found that designs differ in their ability to keep buildings cool and to capture rainwater.
Mark Simmons led the study for the Lady Bird Johnson Wildflower Center at the University of Texas at Austin. "Green roofs have to be done right," he says. For example, he says, "Just having a green roof may not mean anything in terms of preventing water from reaching the street level."
The team put experimental roofs on top of metal insulated boxes, to recreate green roof conditions. The study compared products from six companies. The researchers say they want to help businesses understand how to improve their designs.
Each rooftop had sixteen different kinds of plants native to Texas. The researchers say the presence of native plants likely helped all the green roofs capture water better compared to sedums. Sedums are plants that need little water and often are used on green roofs.
The native plants could take in more water and release more of it to the atmosphere.
And that's the VOA Special English Development Report, written by Jerilyn Watson.
- This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
- There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。
- They designated the new shopping centre York Plaza.他们给这个新购物中心定名为约克购物中心。
- The plaza is teeming with undercover policemen.这个广场上布满了便衣警察。
- The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
- The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。
- His new book is a demonstration of his patriotism.他写的新书是他的爱国精神的证明。
- He gave a demonstration of the new technique then and there.他当场表演了这种新的操作方法。
- The barge was loaded up with coal.那艘驳船装上了煤。
- Carrying goods by train costs nearly three times more than carrying them by barge.通过铁路运货的成本比驳船运货成本高出近3倍。