A Green roof, sometimes referred to as a living roof, is a roof of a building that is partially or completely covered with vegetation. Installing a green roof has become increasingly popular in the City and beyond.
Depending on your preferences, the roof could be extensive – requiring no maintenance at all or an intensive roof top garden that needs regular maintenance but makes for a fantastic amenity space for employees.
There are numerous benefits of installing a green roof to an existing building, or factoring them in to plans for a new build. Here are our views on the top five benefits of a green roof for people and planet.
Poorly insulated roofs are a common feature of many older buildings in the City. This often leads to overheating of the spaces below in the summer, increasing the need for artificial cooling, as well as excessive heating demand during the winter. Adding a green roof to an old build will lead to a decrease in the use of heating and air conditioning, making the building more energy efficient, reducing costs and benefitting the environment.
The lifespan of a standard roof in good condition will be doubled by the addition of a green roof. Waterproofing membranes that protect roofs are worn down and damaged by ultra-violet light and temperature fluctuations all year round. Green roofs are now known to double and even triple the life of the waterproofing membrane by serving as a protective barrier between the roof and the elements. Roof repairs and maintenance can be costly and time consuming, so reducing the frequency at which this work is required, can be greatly beneficial.
Many of the green roofs popping up in the City are extensive. These give the more practical functions such as drainage and reducing energy usage as mentioned above. Many organisations, however, are looking to gain further utility from their green roof by making it an accessible place for their staff to visit and spend time in. The benefits of green spaces to our health and wellbeing are widely known and available outdoor green spaces can be few and far between in the City. An intensive green roof will keep its practical benefits whilst additionally serving as an attractive location with flowers and trees, suitable for meetings and staff breaks as well as providing an area for rest and relaxation.
Figure 1 – This well-managed intensive green roof at 1 Poultry overlooks
the busy Bank junction. (Source: D&D London)
Green roofs can cater for a variety of species that would never be found on a traditional roof and can be a great opportunity to do your bit for wildlife. The roof can be designed with particular species in mind and aim to assist the objectives of local Biodiversity Action Plans. A green roof with a range of wildflowers will be crucial for insects and can crucially support foraging bees in urban environments. They can also provide important habitat for birds. This can help with the conservation of rare species like the Black Redstart, which is a success story in the history of green roofs in London. Many of our green roofs were originally commissioned specifically to support the Black Redstart population, which has now been observed breeding successfully on various roofs, including the flagship roof on the Olympic park buildings.
Built up areas like the City rely on manmade drainage systems to prevent localised flooding and drain excess rainwater. Our traditional drain and sewer system has been outgrown and is no longer sustainable for an ever growing population and changing climate. Many initiatives are being brought in to tackle this increased risk of flooding, and green roof installations are a good solution as part of a larger strategy. Green roofs store rainwater in the plants and substrate and release the water back into the atmosphere. This can significantly reduce peak flow rates, mitigate stormwater runoff, as well as reduce the total volume of rainwater runoff compared to a standard roof.
Other notable benefits worth mentioning include:
-> Green roofs as a natural sound proofer
-> Improvement of local air quality
-> Lessening the urban island heat effect
The London Assembly website has lots of helpful information on green roofs in London and includes a “Green Roof Map” tool where you can view existing roofs in the City.
Written by Jodie Thwaites, Finance and Technology Officer at Heart of the City.
Related Article – Bees in the City: Supporting Communities and the Environment