文章大意：本文是一篇说明文。文章介绍了那种使用现代的、太阳能电池板的建筑属于绿色建筑，但是拆除现有住房，那将是令人难以置信的浪费。幸运的是，有大量相对简单的改变可以使老房子变得环保。能效升级不仅可以拯救地球；它们还可以帮助业主免受不断上涨的电力成本的影响。
2 . 阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。
When we think of green buildings, we tend to think of new ones — the kind of modern, solar-paneled masterpieces. But the US 1 (have) more than 100 million existing homes, and it would be incredibly wasteful to tear them all down.
An enormous amount of energy and 2 (resource) went into the construction of those houses. And it would take 3 average of 65 years for the reduced carbon emissions from a new energy-efficient home to make up for the resources 4 (lose) by destroying an old one. So in the broadest sense, the 5 (green) home is the one that has already been built. But at the same time, nearly half of US carbon emissions come from heating, cooling 6 powering our buildings. They can’t deal with climate change without dealing 7 existing buildings.
The oldest homes tend to be the least energy-efficient, mainly due to the tiny cracks and gaps that expand over time and let in more outside air.
8 (fortune), there are a vast number of relatively simple changes 9 can green older homes. And efficiency upgrades can save more than just the earth; they can help protect property owners from 10 (rise) power costs.
