Sourced from The South African
There are about 500 000 square metres of green space in Chicago in the United States. Many of these are visible, not on the ground, but on building roofs across the city. Green roofs can be seen in a number of other cities around the world.
Green roofs are usually installed on flat roofs with vegetation planted in a growing medium on top of waterproofing, root barrier and cuspate sheeting. The sheeting retains moisture in between rainfall events or manual watering.
Research suggests that these roofs have a number of advantages. These include rainfall management by absorbing much of the rainwater for vegetation growth and the enhancement of biodiversity.
They’re also a social amenity as a visual relief to the dominant concrete surfaces and some studies suggest there are psychological benefits for people overlooking such roofs.
Green roofs are also credited with attenuating extreme temperatures by keeping the rooms below the roof cool in summer and warm in winter.
We set out to study what benefits green roofs might bring to Johannesburg, a city in South Africa’s interior. There are a few buildings with green roofs in the inner city, but these are not common.
Johannesburg’s climate – with high day time temperatures in summer and winter, as well as a distinctly seasonal summer rainfall – has not been previously researched to see whether its buildings might benefit from green roofs.