Take a look at this picture. Looks like a lovely, natural field, right? Well, hard to believe, but it's actually a rooftop in Switzerland:
Since the late '90s, federal law in Switzerland has required every new building with a suitable roof pitch to have a green roof - meaning the building's owner has to plant and maintain some kind of natural greenery up there. As a result, a visual tour of Swiss rooftops is pretty amazing:
The law has also had a notable effect on temperatures. Standard asphalt rooftops can reach temperatures above 66C in some cities, contributing to the "urban heat-island effect" - the tendency for cities to be warmer than the surrounding areas. But a green roof uses soil and vegetation as insulation, meaning temperatures only fluctuate mildly. It can reduce heating and cooling costs by up to 20 percent.
Once green roofs have been in place long enough, they can even become habitats in their own right. This 95-year-old living roof of a water filtration system in Zurich is home to nine species of native orchids that were eradicated from the countryside when the area was converted to cropland:
This is the roof of a hospital in Basel, Switzerland's third most populous city. Although green roofs are picturesque, builders see them primarily as a way to help meet Switzerland's stringent environmental standards:
In Canada, the city of Toronto approved a by-law in May 2009 mandating green roofs on residential and industrial buildings. Today, industrial buildings in T.O. are required to render 10 percent of their roofs green. The largest green roof in this country is the six-acre roof of the Vancouver Convention Centre, which uses indigenous plants and grasses on its West building. Ottawa's Canadian War Museum also features a grass-covered roof.
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