Savannah: You can save money and the planet by changing the color of your roof.

See, the color of your roof has huge impacts on your energy use and your microclimate. Dark roofs are better in cold areas because they absorb solar radiation and trap more heat throughout the day. While light roofs are better where it's warm because they reflect radiation, keeping things cool. And as for regions that have seasons, researchers have developed a coating for your roof that changes color.

One method involves covering the roofs with a black layer topped with transparent cells filled with temperature-sensitive solution. When the solution is cool, it's see-through, letting the black layer show through and absorb radiation. But when it's hot, the molecules collapse and turn the roof white to reflect the heat away.

Roof coatings like this could make houses up to 31.5% more energy efficient, which is how -

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