by Sidonie Carpenter – President, Green Roofs Australia.

Its with great interest that I read your article on Green Roofs are a Cool Idea, parts one and two, published in The Fifth Estate.

It is great to see and hear of so much conversation regarding green roofs finally happening in Australia. It’s definitely a very exciting area with huge potential and I believe an area worth considering in regard to the Australian built environment.

I am a little concerned with some of the facts that you state – in particular the depth of the extensive roof profile being 2–7 centimetres. Extensive roof profiles are typically 10–30 cm with the possibility of any green roof in Australia surviving on less than 20 cm being very slim

Yes there are some roof profiles in Europe and Nth America that are very thin – this would not be viable in Australia with our temperature and water issues.

The roof on Parliament house is over 100 cm thick – yes, simple because its only supporting turf but the soil profile is quote complex.

In regards to PV [photo voltaic] cells and green roofs there has never been such a perfect opportunity for integration of design.

The issue with PV in Australia is actually that its too hot. The optimum running (energy producing) temperature for current technology PV is around 23 degrees – most roofs in Australia, even in winter are more than double this temperature – rendering PVs into what is called a “brown out” and energy productions drops dramatically.

By installing PV on a green roof and dropping the ambient air temperature around the cells you can potentially increase its efficiency by up to 25 per cent.

Well done on your article. The issue of food production/security is a area of great interest and of course the huge opportunity to incorporate it into our urban areas on our roof tops.

I have just been on the judging panel for the Growing Up–Greenroof for Melbourne CBD competition and you will be pleased to hear there were three entries that incorporated food production into their green roof design – with one of the designs taking out third place.

Sidonie Carpenter is President, Green Roofs Australia.

For more information: www.greenroofs.wordpress.com