If you haven't heard of a green roof before, you've probably already guessed what it is. Put simply,a green roof is a layer of vegetation on top of a building, ranging from a thin coating of grass to full-blown garde. A sensible question! Other than to make things look nicer for overhead birds and people in helicopters, what's the point of a green roof? Well, the list of benefits is long. According to Gardenista, a typical four-inch extensive green roof costs approximately $10-20 per square foot, or around £8-17 per square foot. And according to this UK based green roo. Green roofs and solar panels are generally seen as mutually exclusive. This isn't actually the case (see further down the page), but if you're choosing between the two, which woul. Yes! Commonly thought to be mutually exclusive, solar panels and vegetation can coexist on the same rooftop. What's more, when you combine the two together, both perform better. It'.