A few volunteers, some creative problem-solving, and a whole lot of white paint. At the White Roof Project, that’s all it takes to whip up an effective recipe for change.

The New York-based non-profit has its sights set on 2030, by which time it hopes to have painted the world's roofs white. If the people involved can make that happen, the amount of energy saved, they say, will be equal to convincing the world’s population to shut down their power for an entire year. See how it works: