An introduction to the sustainable architectural wonder that is the living roof.
What is a Green Roof?
A green roof is a building roof that is covered – to some extent – in vegetation and a growing medium, planted over a waterproofing membrane.
Also known as living roofs, they supplement traditional vegetation and habitats without disrupting urban infrastructure. They take otherwise neglected urban areas and breathe new, sustainable life and energy into them.
What does a Green Roof do?
There are different types of living roofs that all serve slightly different purposes. But green roofs are primarily designed to:
- Insulate the property and reduce energy bills
- Reduce pollution
- Increase biodiversity
- Mitigate the urban heat island effect
You can find out more about green roof benefits here.
Extensive roofs are the cheapest, simplest type of green roof and they primarily focus on environmental benefits. Intensive roofs can be significantly more expensive because of the plant quantity, quality and size. They’re also far more aesthetically pleasing and allow for garden interactivity. Semi-intensive roofs are a combination of the two.
Their ability to replace a hard, uncompromising – otherwise useless -infrastructure with something aesthetically pleasing and environmentally beneficial is extraordinary. And vastly under-utilised in the UK.
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History of Green Roofs
Arguably the earliest and possibly still the most famous green roofs of all time were the Hanging Gardens of Babylon – considered one of the Seven Wonders of the Ancient World – constructed in 6th century BC. But in reality roofs covered with earth and sod were commonly used for insulation and agricultural purposes.
And sod roofs were widespread across Scandinavia since pre-history. And were commonplace until they were replaced with tiles in the 18th century such is their heating and cooling properties.
Whilst modern green roofs use a system of manufactured layers, this is certainly a more recent phenomenon borne out of necessity. As urban areas grow and grow, the need to protect wild spaces, reduce emissions and runoff is vastly exacerbated.
But the core principles remain the same. Even thousands of years later. An earthen roof insulates a property in the winter and cools it in the summer.
This just wasn’t as much of a problem pre HVAC equipment.
Green Roof Examples
City Hall, Chicago
As part of an initiative to combat the urban heat island effect and to improve urban air quality, the city of Chicago (as part of an EPA study) constructed a semi-intensive green rooftop that cost $2.5 million.
The project was completed in 2001 as part of an EPA study and according to author Michael Berkshire, the green roof saves $5,000 a year on utility bills alone.
The roof has over 20,000 herbaceous plants installed as plugs of more than 150 varieties. The scale of the project is absolutely immense.
Nanyang Technology University, Singapore
The Nanyang Technology University’s key feature is the 45 degree sloping intensive green roof. Complete with courtyard, wall facades, fountains and pond(s) makes this project all the more extraordinary.
Completed in 2006 at a cost of $38 million it’s a sustainable wonder of architectural expertise. It allows students and faculty members to interact with and enjoy the garden, whilst insulating, cooling surrounding air and improving irrigation and drainage.
Fukuoka Prefectural International Hall, Japan
Situated bang in the centre of Fukuoka city, the International Hall’s green roof is one of the most amazing examples of sustainable architecture.
The architect (Emilio Ambasz) wanted to highlight the fallacy that cities are for buildings and suburbs are for parks is wrong.
The 100,000-square-metre-park and 15 terraces were opened to the public in 1995 and it’s innovative design fulfilled a public need for green space and to find a profitable use for the site.
In 2000, a joint study found that rooftop gardens are effective in alleviating the urban heat island phenomenon. There was a 15°C difference between surface temperatures of concrete within the roof garden.