This article was originally published by National Geographic.

With 48 million Americans living below the poverty line, many are faced with difficult decisions between, for example, heating the house or buying groceries. A passive low cost house—super-insulated and airtight to keep energy bills low—can help the poverty alleviation. Habitat for Humanity built six of them for low-income families in Washington, D.C. "It's basically as energy efficient as building gets," says Dan Hines, senior construction supervisor for the project.

The original article can be viewed on the National Geographic website

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