Again, when you're thinking cool and green, the hot tin roof is not necessarily the first material that would come to mind. But then, this isn't the '50s, and we're not just talking about regular metal. "It's not bare," Clark points out. "It's a coated metal."
You start with a coated metal and paint it a light color or add some light-reflecting pigment, and you've got a cool roof. You can even install it over an existing roof. "It's really durable, and a lot of times you can recycle the material," Clark says. You'll also have the benefit of a unique roof that stands out in a sea of shingles.