Living roofs are soaring in popularity, both in residential and commercial projects, due not only to their aesthetics, but also the many environmental benefits they bring to the building. You will note if you visit horticultural events such as Chelsea or Hampton Court Flower Shows that many of the show gardens incorporate green roofs in some way, which is always a good indication of future trends. Here is a brief guide, explaining firstly what green roofs and brown roofs are, before detailing their uses and benefits.
Green Roofs are basically roofs which incorporate planting, often sedum or wildflower and meadow planting, grasses and mosses. In fact, some can even be planted with trees and shrubs. The Roof Gardens in Kensington is a prime example of this. Installing a green roof creates a vegetated surface which provides colour and interest throughout the year. Often, living roofs are used in rural settings and in areas where the buildings need to blend into the background. Green roofs will either be planted or seeded.
There are of course many considerations before installing a green roof, primarily ensuring your roof is suitable, and ensuring it is completely watertight. It is always recommended to get a professional company carry out the work, as you could do more harm than good if not done properly.
Of course, living roofs/wildflower and meadow roofs create a dramatic visual impact, but they also have many other benefits.
Benefits of Green Roofs
1. Photosynthesis – the process of plants absorbing carbon dioxide and releasing oxygen. This is of particular benefit in urban areas.
2. Filter pollutants and dust from the surrounding area, again, a huge benefit in urban areas.
3. Green or living roofs act as an insulating layer on your roof. You should therefore expect to spend less on your energy bills, thus reducing your carbon footprint.
4. Increase in biodiversity – encourage animals such as bees, butterflies and birds into the area. With the current bee crisis, any opportunity to encourage bees into the area is a huge benefit.
5. Living roofs can be fitted with bird boxes to encourage birds, often endangered species, into the area and give them a safe environment to nest.
6. Endangered plants can be introduced into the roof planting.
7. Green roofs can reduce stormwater runoff significantly, which can help alleviate flooding, another very topical issue.
8. Often used as social areas, perhaps on top of office buildings, allowing staff to have somewhere green to escape to in the middle of an urban area. They are also increasingly being installed in public areas, to provide much needed green space in built up areas. A good example of this is on London’s Cannon Street Station.
Brown roofs are very similar to green roofs. The main difference is that whilst green roofs are often installed partly for the aesthetic value, brown roofs tend to be installed for environmental reasons, mainly, to encourage plants and wildlife.
Brown roofs are generally made using recycled materials and local soil. Whereas green roofs are often planted using very specific plants and following structured plans, brown roofs evolve more naturally. Whilst they are called brown roofs as this is the colour they are at the time of installation, they generally turn green over a period of time once the plants have started to establish themselves.
Brown roofs can incorporate water pools, wetland areas, rocks and boulders, basically any materials which will attract wildlife.
Benefits of Brown Roofs
1. Encourages wildlife into the area – brown roofs are specifically designed with this in mind. Particular plants may be introduced with the sole aim of encourages bees or butterflies. Wetland areas will encourage other types of insects and animals.
2. Brown roofs utilise soil and rubble which has been left behind after construction work. This ensures that wildlife which may have been displaced when construction work began, are encouraged back into the area.
3. As with green roofs, air quality is improved, which is particularly beneficial in inner city areas.
4. As brown roofs are made using recycled materials, they are the greener alternative.
5. Brown roofs generally have all the benefits of a green roof. They may take slightly longer to develop and flourish, but the environmental benefits will more than make up for that.
We in the UK are in some ways falling behind other countries with regards to green and living roofs. This has now been recognised, and a policy has now been written up to introduce more of this type of roof to both new and existing buildings wherever possible.