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When we think of green buildings, we tend to think of new ones – the kind of high-tech, solar-paneled masterpieces that make the covers of architecture magazines. But the U.S. has more than 100 million existing homes, and it would be 47 incredibly wasteful to tear them all down and 48 replace them with greener versions. An enormous amount of energy and resources went into the construction of those houses. And it would take an average of 65 years for the 49 reduced carbon emissions from a new energy-efficient home to make up for the resources lost by destroying an old one. So in the broadest 50 sense, the greenest home is the one that has already been built. But at the same time, nearly half of U. S. carbon emissions come from heating, cooling and 51powering our homes, offices and other buildings. "You can't deal with climate change without dealing with existing buildings," says Richard Moe, the president of the National Trust.
With some 52 exceptions, the oldest homes tend to be the least energy-efficient. Houses built before 1939 use about 50% more energy per square foot than those built after 2000, mainly due to the tiny cracks and gaps that 53 expand over time and let in more outside air.
Fortunately, there are a 54 vast number of relatively simple changes that can green older homes, from 55 historic ones like Lincoln's Cottage to your own postwar home. And efficiency upgrades (升级) can save more than just the earth; they can help 56 protect property owners from rising power costs.
A) accommodations B) clumsy C) doubtful D) exceptions E) expand
F) historic G) incredibly H) powering I) protect J) reduced
K) replace L) sense M) shifted N) supplying O) vast
