In the late 1960s, many people in North America turned their attention to environmental problems, and new steel-and-glass skyscrapers were widely criticized. Ecologists pointed out that a cluster of tall buildings in a city often overburdens public transportation and parking lot capacities.
Skyscrapers are also lavish consumers, and wasters, of electric power. In one recent year, the addition of 17 million square feet of skyscraper office space in New York City raised the peak daily demand for electricity by 120, 000 kilowatts-enough to supply the entire city of Albany, New York, for a day.
Glass-walled skyscrapers can be especially wasteful. The heat loss through a wall of half-inch plate glass is more than ten times that through a typical masonry wall filled with insulation board. To lessen the strain on heating and air-conditioning equipment, builders of skyscrapers have begun to use double-glazed panels of glass, and reflective glasses coated with silver or gold mirror films that reduce glare as well as heat gain. However, mirror-walled skyscrapers raise the temperature of the surrounding air and affect neighboring buildings.
Skyscrapers put a severe strain on a citys sanitation facilities, too. If fully occupied, the two World Trade Center towers in New York City would alone generate 2.25 million gallons of raw sewage each year-as much as a city the size of Stanford, Connecticut , which has a population of more than 109, 000.
2014秋外研版(三起)四上Module 2《Unit 2 What are you doing》ppt课件2
2014秋外研版(三起)四上Module 1《Unit 2 It’s at the station》ppt课件3
2014秋外研版(三起)四上Module 2《Unit 1 She’s reading a book》ppt课件2
2014秋外研版(三起)四上Module 2《Unit 2 What are you doing》ppt课件6
2014秋外研版(三起)四上Module 3《Unit 2 What’s the elephant doing》ppt课件2
2014秋外研版(三起)四上Module 10《Unit 2 Merry Christmas》ppt课件4
2014秋外研版(三起)四上Module 6《Unit 2 Happy Halloween》ppt课件2
2014秋外研版(三起)四上Module 1《Unit 1 Go straight on》ppt课件2
2014秋外研版(三起)四上Module 2《Unit 2 What are you doing》ppt课件3
2014秋外研版(三起)四上Module 3《Unit 1 What are they doing》ppt课件1
2014秋外研版(三起)四上Module 1《Unit 1 Go straight on》ppt课件1
2014秋外研版(三起)四上Module 2《Unit 1 She’s reading a book》ppt课件1
2014秋外研版(三起)四上Module 1《Unit 1 Go straight on》ppt课件3
2014秋外研版(三起)四上Module 3《Unit 1 What are they doing》ppt课件4
2014秋外研版(三起)四上Module 10《Unit 1 We have a big family dinner》ppt课件1
2014秋外研版(三起)四上Module 10《Unit 2 Merry Christmas》ppt课件2
2014秋外研版(三起)四上Module 3《Unit 1 What are they doing》ppt课件2
2014秋外研版(三起)四上Module 10《Unit 1 We have a big family dinner》ppt课件2
2014秋外研版(三起)四上Module 3《Unit 1 What are they doing》ppt课件6
2014秋外研版(三起)四上Module 2《Unit 1 She’s reading a book》ppt课件4
2014秋外研版(三起)四上Module 2《Unit 1 She’s reading a book》ppt课件3
2014秋外研版(三起)四上Module 6《Unit 1 Can I have some sweets》ppt课件4
2014秋外研版(三起)四上Module 6《Unit 2 Happy Halloween》ppt课件1
2014秋外研版(三起)四上Module 6《Unit 1 Can I have some sweets》ppt课件2
2014秋外研版(三起)四上Module 1《Unit 1 Go straight on》ppt课件5
2014秋外研版(三起)四上Module 4《Unit 1 Do you want some rice》ppt课件1
2014秋外研版(三起)四上Module 3《Unit 2 What’s the elephant doing》ppt课件1
2014秋外研版(三起)四上Module 1《Unit 1 Go straight on》ppt课件4
2014秋外研版(三起)四上Module 10《Unit 1 We have a big family dinner》ppt课件3
2014秋外研版(三起)四上Module 3《Unit 2 What’s the elephant doing》ppt课件5