Green roofing is a way to create a contained green space on top of a structure to support drainage, thermal performance, and biodiversity. This was standard practice in many countries for over a 1000 years. In cold climates, green roofs help retain heat and, in hot climates, keep buildings cool.
Le Corbusier & Frank Lloyd Wright made extensive use of green roofs. The 1960’s brought renewed interest in Northern Europe.
In 1989, Germany had 1 million sqm of green roofs. In 1996, this was 10million sqm. The market was largely stimulated by state legislation and municipal government grants. Over 7.2million sqm were constructed in 2019.
There are 2 types- Extensive and Intensive.
Typically designed as a roof covering, not for access. These are not complicated to construct, and are normally on residential scale roofs.
Extensive Green Roof System
Advantages
- Lightweight
- Low maintenance
- Suitable for large areas
- Little/no irrigation systems
- Relatively inexpensive
- Relatively little technical expertise required
Disadvantages
- Limited choice of plants
- Usually no access for amenity
Intensive Green Roof System
- More technical, these systems are normally on flat roofs of commercial buildings or apartment blocks, creating private open space and food-growing areas.
Advantages
- Can have a shallow roof profile of grasses, mosses, sedums, up to pitch of <45 degrees
- Greater diversity of plants
- Good insulation properties
- Diverse Utilisation park, growing food, open space
Disadvantages
- Greater roof load
- Need for complex irrigation/drainage systems
- Higher Cost
- Expertise required
Reasons to use green roofs
- Replaces footprint of building with green space, which can be useful in planning applications
- Lowering air temperatures in cities
- Reducing stormwater run-off
- Lowering carbon dioxide levels
- Encourages biodiversity and wildlife
- Create space for roof top garden/park or for growing food in cities