In the era of climate change, every surface that offers a habitat to plants and animals counts. That includes house roofs, garden sheds, garages, car porches and dustbin boxes – even the tops of bird houses can be greened to nurture biodiversity.
Cultivated roofs create so-called stepping stone biotopes – places that serve as reproduction or retreat sites for different and often endangered species.
Whole parts of towns and cities are effectively sealed, since many animals, especially insects, cannot travel a long way from one large green area to the next. Green roofs then function like stepping stones that shorten the distances.
There are even more reasons for planting roofs, starting with their ability to reduce overheating of the surface and building interior.
“Green roofs not only bring natural variety to inner cities, but they also counteract the heating of the climate in the hot months…”
“Green roofs not only bring natural variety to inner cities, but they also counteract the heating of the climate in the hot months,” says Annika Dobbers, advisor to the “More Green On The House” project underway in the state of North Rhine-Westphalia, Germany.
While a normal garage roof can reach 80ºC in hot weather, with greenery it is just 30ºC.
“At the same time, a green roof is always a fine dust filter and a good storage for rainwater,” says Dobbers, who assisted her local consumer advice centre in launching the greening project.
This is important during continuous and heavy rainfall to prevent strain on the sewers and flooding. Another advantage, according to Germany’s BuildingGreen Association (BuGG), is that the plants help reduce everyday noise inside and outside.
Green roofs come in two forms: extensive and intensive. The intensive roof reaches a height of between 25cm and 100cm.
Shrubs and trees find room for their roots here, so it is a kind of roof garden that requires a higher structure and also more effort.
Extensive green roofs are more common. The roof structure of extensive greening is only between 8cm and 15cm high – so it also works for planting smaller roofs, like those on bicycle shelters, with succulents for example.