The green roof as an air enhancer

That a green roof helps improve air quality should really come as no surprise. Plants on the roof - or equally well against the facades - act as filters, just as trees do. They capture and retain common pollutants. Think of particulate matter, CO2, ozone and nitrogen oxides (NOx). This effect can be felt and measured in the immediate vicinity of a green roof. University research in some major cities also demonstrates this. For example, in 2007, researchers in Chicago installed green roofs on some 300 buildings, totaling 27.87 acres. After the first year, the roofs together removed 1,675 kg of air pollutants from their surroundings. In the following years, that share increased steadily thanks to the continued development of the plants. The lessons from this study suggest that a green roof of 1,000m² can capture about 6kg of air pollutants on an annual basis.

Furthermore, the researchers learned that sedum, a commonly used plant on green roofs, annually stores about 1.23 kg of_CO2 per square meter. So an 813m² sedum roof manages to capture 1 ton of CO2 annually. This offsets about 10,000 km of driving a gasoline car. And in return, the roof provides oxygen.

Catching heavy metals

Researchers in Toronto, Canada, looked a little more broadly in their study and looked at the different combinations of trees, shrubs, green facades and green roofs in the city. Their research also confirms that green roofs have a positive effect on pollutant capture. A 1,000m² grass roof can remove about 2 tons of particulate matter annually. Compared to particulate matter emissions from cars, one square meter of green roof is enough to remove the emissions of one car.

Furthermore, it appears that green roofs and green facades also manage to absorb heavy metals. Leaves absorb up to 95% of cadmium, copper and lead and 16% zinc from their immediate environment. An extensive green roof of 20m² will remove about as many pollutant metals from the air as a medium-sized tree.

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That a green roof helps improve air quality should really come as no surprise. Plants on the roof - or equally well against the facades - act as filters, just as trees do. They capture and retain common pollutants. Think of particulate matter, CO2, ozone and nitrogen oxides (NOx). This effect can be felt and measured in the immediate vicinity of a green roof. University research in some major cities also demonstrates this. For example, in 2007, researchers in Chicago installed green roofs on some 300 buildings, totaling 27.87 acres. After the first year, the roofs together removed 1,675 kg of air pollutants from their surroundings. In the following years, that share increased steadily thanks to the continued development of the plants. The lessons from this study suggest that a green roof of 1,000m² can capture about 6kg of air pollutants on an annual basis.

Furthermore, the researchers learned that sedum, a commonly used plant on green roofs, annually stores about 1.23 kg of_CO2 per square meter. So an 813m² sedum roof manages to capture 1 ton of CO2 annually. This offsets about 10,000 km of driving a gasoline car. And in return, the roof provides oxygen.