More Roof Gardens Wanted – Ecologist

The Christchurch rebuild provides a unique opportunity for a rooftop sea of greenery and exotic plant life, ecologist Colin Muerk says.

This is not the first time the need for a greener rebuild has come up.

The green roof concept is quickly catching on internationally and some towns have made them a requirement of a new build, Muerk says.

However, the responsibility should not be on businesses alone. Residential homes are just as viable, he says.

Muerk will be speaking about the benefits of green roofs at a Greening the Rubble installation in Cranmer Square.

The installation features four green roof examples which have been constructed lower to the ground to allow people to see more of how they work.

While it is difficult to adapt an existing roof to be a green roof, Canterbury has to build a lot of structures from scratch which is much simpler.

The load on structures is quite high when you factor in soil and water weight after rain. They are shallow gardens and support exotic species which thrive on low soil levels, high exposure and limited water.

Muerk says the gardens are of huge environmental benefit.

“In a way they’re kind of islands or an oasis which support some rare species. They’re basically quite valuable.”

The success of a green roof, and species used, will vary depending on rainfall, sunlight hours, how exposed it is and how deep the soil is. Many are fitted with filtration systems or stormwater collectors. They require waterproofing and thick membranes to prevent leaks and roots growing through the ceilings.

It is big effort but the rewards are high, Muerk says. In Christchurch, office workers could have access to rooftop green space and aesthetically it would add value to the city.

Some places give a subsidy to green roof businesses just like we have for residential insulation.

“I think it’s just a cool thing to do, really,” he says.