Reduction of Urban Heat Island Effect
Green roofs are one of the most effective ways to
reduce the ambient air temperature in urban areas.
During summer the temperatures in cities are approximately 5-7°C higher than
in the countryside due to buildings and
roads heat absorption and the temperature on the
traditional roof can be up to 40°C higher compared
to the green roof.
According to research carried out by the Tyndall
Centre for Climate Change there is a need of
10% more greenery in towns to mitigate the UHI Effect.
A major advantage of green roofs is the reduction
of storm water runoff, which leads to a decrease
of the burden on sewer systems by 50-90%
in summer, depending on the green roof design and local climate.
Green roofs have influence on cost reduction
due to low or no need for raincatching cisterns
and similar equipment which is usually used
for storm water management.
Rainwater retention capability helps to limit
accidents caused by heavy rainfalls.
Through natural bio-filtration, green roofs prevent
contaminants and toxins from reaching streams
According to Kohler & Schmidt research (1990)
95% of the lead, copper and cadmium sulphide
and 19% of the zinc coming from the rainwater
remains in the substrate, which helps to improve
local water quality.
Green roofs help to reduce the amount of CO² in the air,
which is considered one of the most important
causes of global warming. 1m² of a green roof
can absorb 5 kg of CO² yearly.
Additionally, due to reduced energy consumption
there is a further impact on carbon dioxide reduction
by 3.2kg yearly.*
As a perspective, 1m² of green roof can absorb the
same quantity of CO² as a regular car would emit
during a 80km drive.
The plants on green roofs can also capture
airborne particles such as smog, heavy metals
and volatile organic compounds from the local
atmosphere which has a positive effect on air
quality and health of inhabitants. Researchers
estimate that 1m² of a green roof can help to
absorb 0.2kg of airborne particles from the
air every year**.
As urbanisation increases, ensuring biodiversity
is one of the key requirements for local councils.
Green roofs can provide a habitat for various
species and restore the ecological cycle
disrupted by urban infrastructure.
*United States Environmental Protection Agency EPA - Reducing UHI: Compendium of Strategies