Sustainable House Day: How a green roof retrofit made a block into a community
Willow Aliento | 1 September 2016
Ahead of Sustainable House Day, being held across the country on 11 September 2016, we’re taking a look at some of the best homes on display.
With a whole lot of sweat equity and the help of a grant, the residents of a three-storey 1950s apartment block in St Kilda retrofitted a 646 square metre green roof.
The result is not only improved stormwater management, reduced urban heat island effect and improved insulation for apartments, but also a space that has generated a real sense of community, according to resident Sonia Bednar.
Bednar says the project started with her, her partner and four other residents forming a committee to research the possibility of having a green space on top of the building. The block of 23 apartments otherwise had no common green open space and the roof was used only for drying laundry.
She says the group knew the environmental benefits would be enormous.
They found out from the City of Port Phillip that the Victorian state government was offering grants for water management initiatives. The green roof would act to absorb stormwater, and thereby mitigate flash flooding, Bednar says. The pitch was successful and the project was awarded $200,000.
The residents contributed various kinds of sweat equity, including developing a website to educate others about how the project was developed and its progress as it grows.
Bednar says that once the grant was secured, it was not difficult to convince the strata community to go ahead with the project. There were a number of concerns raised, such as the structural risks, so a structural engineer was engaged to assess the roof’s bearing capacity.
To mitigate the risk, the garden installed by Fytogreen has a very shallow substrate 120mm deep, so the plantings are mostly hardy native grasses, climbers and creepers.
There are also plantings of rosemary and lavender for bees, and Bednar says they hope to add a beehive at some point. There are also four raised box beds for growing vegetables placed on structural strong points, and there is strong interest in more of these being added, she says.
Another concern was leakage, so Bednar says research was put into finding the right membrane to go under the green roof. The one they chose is like a pool liner, she says, and sits above the roof structure. A leak detection system has also been installed that can pin-point any leak to within an area the size of a 20 cent coin, so only a small part of the garden would have to be dug up if a leak occurs.
She says that if the project had not received the grant, it would have cost approximately $10,000 per owner. However, she says the Growing Green Guide produced by City of Melbourne says that adding a green roof increases property values by around 11 per cent. That means the apartments, currently worth around $600,000 each, would now have a value uplift of around $66,000.
“But we haven’t had any sales yet to test that,” she says.
That’s because no one wants to leave, including families with children that were thinking about moving so they could have a backyard.
“We call it our upstairs backyard,” Bednar says.
The apartments are around 60 per cent owner-occupiers and 40 per cent owned by investors and tenanted, she says. Even the investor owners were happy for the project to go ahead due to the value it added to the property.
Beyond the dollar values and the environmental benefits, the green roof has created a social element that has made the block “such a lovely community”, she says.
It is an element of common good, where everyone works to nurture and maintain the garden and now has a shared interest. As a community, they have held events in the space, including an outdoor cinema night. The food beds are producing seasonal vegetables people share, and there is an ongoing engagement in new ideas for what can be done in and with the garden.
Bednar says she wants to explore some of the native plants in terms of their edibility and culinary uses, including the saltbush varieties that are part of the garden.
The roof project has also led to other sustainability initiatives, she says.
The energy use of the external lights was monitored, and solar PV considered as a measure to offset that energy. However, their usage was not considered high enough to justify the spend, and instead the wattage of common area lighting was reduced.
They are looking at solar on an apartment-by-apartment basis instead, and Bednar says an area of the roof has been left un-greened that can be used to install a “solar bank” for the apartments.
The block also had a visitor’s parking spot that has instead been converted to install bicycle racks for residents, and other spots around the property have also had bike racks installed.
Two water tanks have been installed that provide water for ground level gardens, and Bednar says the community is looking at adding more water tanks. These could be used to irrigate the roof garden if the water was pumped up, she says, or it may be more effective to use them the water for some of the apartments’ toilets.
Another initiative Bednar says is currently being researched is how the residents can separate the water bills, so instead of one whole-building bill that is split equally between apartment owners, everyone is charged for what they actually use.
Bednar says having a common water bill means there is not as much consciousness around saving water as there might otherwise be.
“The garden has made people more keen to look at other sustainability initiatives,” she says.