White roofs are better than green roofs, and everything’s better than black
We’re all on board with the idea that black roofs are so out. But scientists are still establishing what the best alternative is. The most popular alternatives to black are white and green, i.e. painting the roof white to reflect heat or growing plants on it. You’d think a green roof would be best — imagine growing vegetables in your very own sky garden! — but in reality they’re not so great. Gardening’s hard enough when you don’t have to climb out on top of the house to do it, and a new study shows that white roofs are better for the environment anyway.
Popular Science describes new research from Lawrence Berkeley National Laboratory:
White roofs reflect sunlight and heat so well, they help counter global warming, the team found. Green roofs don’t reflect as well. However, both kinds of roofs keep their own buildings cool on hot days. Green roofs actually save owners more on their energy bills, because evaporation from the plants makes them better at cooling buildings in the summertime, while in the winter, they help hold in heat because they’re more insulating.
Nevertheless, over 50 years, green roofs cost more than both black ones and white ones because the plants are expensive to install, the lab found.
So there you go. Let’s paint the town white.
White Roofs Keep Cities Cooler Than 'Green' Ones, Study Finds, Popular Science.