Jul 28, 2020

Green Roofs: Combining Construction With Nature

Blenheim provide green roof installation and maintenance services. To most, this is a new technology which has come about as society has become more environmentally aware. However, green roofs have been around for hundreds of years.

Take one of the ancient wonders of the world; The Hanging Gardens of Babylon, a huge palace covered in a carpet of flowers and greenery. Or perhaps Viking architecture, where grass-covered houses nestled into the hills were commonplace.

A viking style turf house. Source:

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As the population grows and the public become increasingly conscious of climate change; with summers hotter and drier than ever, the need to prioritise sustainability in construction is paramount. 

What are green roofs?

Put simply, a green roof is an area of living flora installed artificially onto the roof of a building in place of a conventional roof. Green roofs come in a variety of types from the low maintenance sedum roofs to larger more complex gardens with shrubs and trees. They offer several advantages: 

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• Green roofs reduce energy consumption by thermally insulating buildings.

• Green roofs can reduce storm water runoff by as much as 60-79% (Kholer et al, 2002), helpful in areas susceptible to flooding.

• Green roofs create natural habitat for urban wildlife.

• Green roofs absorb and store carbon dioxide from the atmosphere, the main greenhouse gas. This process, called carbon sequestration, is thought to be essential in slowing global warming.

• More visually appealing.

• Green roofs absorb pollutants including dust particulates, Sulfur dioxide, Nitrogen dioxide and Carbon monoxide, improving air quality.

• Increase building sound insulation.

• Increase building fire resistance.

• Increase longevity of roof membrane by protecting it from the suns UV rays and heat damage. (green roofs create a cool microclimate through evapotranspiration).

"London will experience increasing risks of flooding, overheating and drought, through hotter drier summers and warmer wetter winters.

Living roofs and walls – green roofs, roof terraces and roof gardens – are key to providing living space, adapting the city to the more extreme climatic conditions and reducing energy use and CO2 emissions."

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- from a report produced by Design for London and the Greater London Authority’s London Plan and Environment Teams along with the London Climate Change Partnership.

How are green roofs installed?

Green roofs are made up of several layers: the first layer is the waterproof and drainage area. The second is the organic substrate and the third is the vegetation layer. Once the waterproof/drainage layer has been leak tested and installed, it is simply a case of laying the substrate and unrolling the vegetation layer (sedum, wildflowers, grass etc!).

How are green roofs maintained?

It's crucial to maintain green roofs to ensure that your intended vegetation is established and isn't taken over by invasive species. Certain species may colonise green roofs, their seeds usually coming from wind dispersal, animals, or contaminated substrate.

It follows that the roof must be monitored and tended to regularly for the first year following installation. After this, maintenance can become less frequent. 

Maintenance activities include removing unwanted materials such as dead plant matter, weeds or mosses, and replenishing substrate where necessary.

REFERENCES

Kholer et al, 2002 -