The modern idea of making a green roof started in Germany in the 1960s. In Scandinavia they have had sod roofs for centuries. It is estimated that 10% of roofs in Germany have been ‘greened’. It is a growing phenomenon with a number of benefits.
🌴 A green roof is when a roof is covered with grass, trees, shrubs and even ponds. Putting potted plants on the roof is not considered to make a roof green. That is not to say that potted plants are the roof is not a good idea.
There are two types of green roof: intensive and extensive. Intensive green roofs have thick vegetation on the roof, including small trees. They need a lot of maintenance such as watering, pruning and fertilizer inputs. Extensive green roofs have a shallow layer of soil and need typically maintenance only once a year. Extensive green roofs have plants and smaller shrubs. The traditional Scandinavian sod roofs are on pitched roofs rather than flat roofs and need less maintenance since the angle of the roof means rain water runs off and places less pressure on the protective membrane of the roof.
Having a pond on a roof is considered to make a roof green because it supports an eco-system and the pond can be used to treat grey water waste from a building.
🌴 Green roofs or ‘living roofs’ usually require the alteration of a roof. A waterproof membrane is needed as well as a root barrier and drainage and irrigation systems. It is not cheap to make a green roof but there are a number of benefits to making roofs green.
- Reduce heating costs because the green roof adds insulation or thermal resistance to a building.
- Reduce cooling costs by evaporative cooling. Cooling costs can be reduced by 50% to 90%
- Similarly, tests have shown that green roofs reduce the heat island effect in cities, and can actually reduce the average temperature of a city in the summer.
- Reduce storm water run-off. Rain water is used rather than becoming a cost negative load for city drainage systems to deal with.
- Green roofs create natural habitats for insects, birds and other animals.
- Green roofs filter carbon and pollutants from the air and also heavy metals from the rain.
- Green roofs help to reduce noise pollution.
- Green roofs provide more space for agriculture in a city.
- Green roofs add LEED points to a building’s design.
In conclusion, green roofs are of major importance to sustainable design and can do a lot to conserve, recycle and make buildings more energy efficient. As environmental conditions deteriorate in urban centers the more architects and home owners will turn to green roofing to find ways to reverse the effects of climate change, pollution and resources depletion.