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 __incredibly__ wasteful to tear them all down and __repleace__
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 __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 __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 __powering__ 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 __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 __expand__ over time and let in more outside air.
　　Fortunately, there are a __vast__ number of
relatively simple changes that can green older homes, from __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 __protect_ property owners from rising power costs.