There are several different types of green roofs. Intensive roofs are thicker and heavier more like roof gardens and require regular maintenance. Extensive roofs are lighter and typically sedum based, requiring less maintenance, often only once a year depending on the location of the roof. Typical requirements of an extensive roof is yearly fertilizing and weeding, and in autumn clearing of leaves.
Image: Barclays Tower, Canary Wharf green roof at 160m high above the city
Green roofs are affected by local conditions and this affects how they look, sedum will thrive or die in different conditions. Green roof sedum is typically grown using several different varieties so that when the predominant variety for the location thrives, this can then take over from any sedum that dies. Summer drought and incorrect laying are also high factors in green roofs dying. With pitched roofs the design should allow for the sedum and water to be retained at the highest point.
Image: Green roof with stones for biodiversity
What can a green roof do for BREEAM and Code for Sustainable Homes?
- Contributes to the number of species for Ecology points.
- Green roofs can contribute to SUDs credits in the Code and BREEAM. Due to the levels of soils and substrates in green roofs these attenuate the water and delay entry into the system.
- Post Construction reviews are now common place in BREEAM and Code assessments. This means that the green roofs need to be properly established on completion.
Image: Green roof in winter
Note: there aren’t any BREEAM or Code credits awarded simply for having a green roof but it does contribute to other credits.