On April 30th, Toronto will become the first city in North America with a bylaw that requires roofs to be green. And we're not talking about paint. A green roof, also known as a living roof, uses various hardy plants to create a barrier between the sun's rays and the tiles or shingles of the roof. The plants love the sun, and the building (and its inhabitants) enjoy more comfortable indoor temperatures as a result. Toronto's new legislation will require all residential, commercial and institutional buildings over 2,000 square meters to have between 20 and 60 percent living roofs. While this is the first city-wide mandate involving green roofs, Toronto's decision follow's in the footsteps of other cities, like Chicago and New York.