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Green Roofs for lower temperatures and cleaner air

2024-04-05
| Policy Research and Advocacy Team, Friends of the Earth (HK)



Hong Kong is known for being a concrete jungle with high temperatures and poor air circulation due to the heat island effect. For every 1°C increase above the average temperature of 28.2°C in Hong Kong, mortality rate rises by 1.8%.[1]Tree planting and green landscaping can help alleviate the heat, but with limited spaces on the ground, are there other suitable places? Green roofs can be a solution, by removing pollutants and greenhouse gases emissions, reducing heat transfer, and minimising stormwater runoff.[2]

Urban temperatures are higher due to heat island effect (Source: Climate Central)

The government has implemented several policies to support green roofs. New large-scale government buildings for instance need to include greenery elements and aim for BEAM Plus certification.[3]Private developers are also offered gross floor area concessions if they include green features into new projects.

Green roof on 8 Bay East, a commercial building in Kwun Tong (Source: HKGBC)

The current policies are still lacking however. For example, the new buildings are not required to have a minimum percentage of green roof coverage, unlike in Beijing and Tokyo, which mandates at least 30% and 20% of respective available roof space to be covered with green roofs.[4],[5]Limited government funding for green roof safety inspection has also hindered its adoption in the city.[6]

Hong Kong could reference other cities to expand the coverage of green roofs. In Toronto, buildings with a gross floor area greater than 2,000 square metres must include a green roof covering 20% to 60% of available roof space.[7]Whereas in New York City, all new buildings and existing buildings undergoing major roof renovations must have 100% of available roof space covered by solar panels, green roofs, or a combination of both.[8]

Canoe Landing Campus, an educational institute in Toronto with green rooftop design (Source: Yanko Design)

Green roofs can mitigate heat island effect, lower building temperature, and improve air quality. Toronto and New York City have shown us how we can encourage wider green roof adoption across the city. Hong Kong should popularise green roofs to bring nature back to the concrete jungle.

 

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