Green-roofing – growing vegetation on rooftops – could help lower air pollution once the COVID-19 lockdown lifts, according to an environmental economist who has been greening roofs for 10 years.
The green technology was developed in Greece in the early 2000s and Vanya Veras and her business partner Pia Vassallo have brought it to Malta.
They have recently begun beautifying Maltese roofs with indigenous or endemic plants, which thrive with very little maintenance.
“The system has to be very resistant to drought. It has to be light, because of our roofs, and the plants have to be strong enough to withstand the equivalent of a hairdryer being held to them for six to nine months of the year,” says Vanya.
The roof gardens are installed using a copy of the rock in the garigue, one of the natural habitats in Malta, and a combination of Mediterranean garigue plants to create a self-sustaining resilient ecosystem.
Each 100 square metres of green roof absorbs up to 18 tons of CO2.
So how many green roofs would it take to offset all the CO2 emissions on the island - about three million tons per year?
“Assuming they remain high after the return of traffic jams and flights, around half of all the surface area of buildings in Malta would need to be greened to absorb most or all of that pollution.”
If an entire roof is covered with vegetation in this system, electricity bills could drop by 75 per cent since the plants improve the building’s energy efficiency by shading the roof and pulling excess heat out of it as water evaporates through the leaves, she explained.
Part of the service the pair offer through their company Vivacity, which also installs garden walls and vegetable patches, is to look after a green roof for a year.
“After that you get a wild field on your roof, which flowers according to the seasons,” she said. “You have to do absolutely nothing unless you wish to prune and have some kind of landscape design.”
The garden is attached to an irrigation system with a timer and only requires a little watering in the summer months.
Apart from the aesthetic value of that patch of greenery, the green roofs act as an effective sound barrier, reduce flooding and urban heat, and improve biodiversity, Vanya says.