Humans have been decking their roofs with grass or sod for hundreds of years, maybe thousands, because it insulates in colder climates. Northern Europeans, like the inhabitants of Denmark's Faroe Islands, cover their roofs in sod and grass. Heck, even my great-great-grandmother lived in a sod-roof hut in Kansas until the family moved into a more traditional home in Illinois.
Now, we have even more options: plant a green roof, modern style, with a layer cake of membranes to absorb and direct water, and perhaps a mini farm to supply your vegetable needs. Or, paint your roof white, to deflect as much as, some some, 70 percent of sunlight, keeping your building cool without the air con. My colleague Gabe and I were discussing which might be better.Well, some buildings, such as at the University of Amherst in Massachusetts are going for both - a little green roof here, a little white roof here. And now researchers at MIT have just announced that you can sort of have it all: they've developed roof tiles that change color depending on the temperature. Hot summer day? The tiles turn white. Cold, drizzly autumn day? Black, which absorbs as much as sun, they say, as the white reflects.I couldn't help bringing up, however, that while green roofs might not work for every structure (they're heavy, for instance), they do provide quite a few benefits that white and black roofs don't. For example, in addition to cooling a room by several degrees, they can filter and slow rain water, which, if collected, can be used to flush toilets. They reduce the urban "heat island" effect, which is basically the phenomenon of so many black roof tops making a city even hotter. They provide space for growing a little food. And they even provide some habitat for migratory birds and other species.So, anyone planning on "greening" their roof - with paint, tiles, or living things?
