The Growth of Living Roofs
No longer the domain of hippies – or hobbits – a green roof is a hardworking partner in keeping your house sustainable
By now we all know the first step to a sustainable home: insulation that maintains the interior at a comfortable temperature, no matter how hot or cold it gets outside. The next step on the journey is water management – collecting rainwater to supply toilets, washing machines or the garden. But equally important is minimising water run-off into increasingly over-burdened stormwater systems (water runs off all that concrete, roofing and paving rather than being absorbed into the land). A green roof – plants growing in an insulating substrate atop the roof of a building – helps solve both problems: insulating the house while absorbing water (and cooling too, since it doesn’t have a reflective surface bouncing the sun’s rays about).
Up until now, it’s been a fringe option, expensive and complicated. But with more and more suppliers bringing what they’ve learned in commercial applications into residential projects, and the Green Roofs Australasia organisation that shares research suitable for Australian and New Zealand conditions, it is becoming more accessible. Start with these inspiring projects at home and abroad.
Up until now, it’s been a fringe option, expensive and complicated. But with more and more suppliers bringing what they’ve learned in commercial applications into residential projects, and the Green Roofs Australasia organisation that shares research suitable for Australian and New Zealand conditions, it is becoming more accessible. Start with these inspiring projects at home and abroad.
Germany is one of the leading countries in green roof architecture, so it is no surprise that former Berlin architects Schulze Poursoltan have brought the principles of healthy architecture, including non-toxic building materials such as this roof, to New Zealand. Green roofs do require special documentation for building consent and code of compliance sign-off from local council inspectors.
Because green roofs can weigh up to 150kg per square metre (that’s for 100 millimetres of substrate, planted and wet) the roof supports and walls must be designed by an engineer. You also need to think about drainage, as you don’t want soil run-off to clog drains and pipes and flood the roof. Designers recommend having a band of about a 300 millimetres (stones or pavers) around the edge of a green roof. Vents ensure that condensation does not build up in the ceilings below the roof.
In this Australian project by Objects, designers have also had to ensure that the substrate does not slide down the slope of the roof, and have used a compact, well-rooted turf.
In this Australian project by Objects, designers have also had to ensure that the substrate does not slide down the slope of the roof, and have used a compact, well-rooted turf.
In this Christchurch office space, the roof uses sedums and succulents to create a brightly coloured view from the upper floors.
Gardens such as these may take time to establish, and bald patches may need re-planting as growth will be uneven in parts of the roof that are in a sun- or rain-shadow.
There are two main systems for roofs – one using an applied substrate such as Nuralite, a waterproof membrane similar to that used on flat roofs under decking or tiles. It requires appropriate foundation substrate (usually concrete or engineered plywood), and skilled workmanship by licensed applicators so there is no risk of the roof leaking and failing.
Polythene, foam insulation and a drainage layer (a cupped product called Plazadeck to catch water, and a geo textile to prevent soil clogging) are applied before the special soil-growing medium and planting is installed.
There are two main systems for roofs – one using an applied substrate such as Nuralite, a waterproof membrane similar to that used on flat roofs under decking or tiles. It requires appropriate foundation substrate (usually concrete or engineered plywood), and skilled workmanship by licensed applicators so there is no risk of the roof leaking and failing.
Polythene, foam insulation and a drainage layer (a cupped product called Plazadeck to catch water, and a geo textile to prevent soil clogging) are applied before the special soil-growing medium and planting is installed.
Alternatively, New Zealand company Stormwater360 has pioneered LiveRoof, a pre-vegetated, modular hybrid green roof system. The plant modules are pre-grown so the green roof is already established and there aren’t the usual maintenance costs to tend the baby plants and address soil issues until the roof matures.
Mike Titchener from Stormwater360 says the right mix of low organic and high inorganic planting medium, and at least three months of intensive care before the roof is installed, means there are no weeds and no dying plants in the hot, wet and dry micro-climates on a roof.
The company has numerous New Zealand native or sedum planting options. A showpiece for the technology is the Tuhoe’s Te Uru Taumatua, a registered Living Building Challenge, where the modular roof ensures clean water enters the storm water system (and there is up to 80 per cent less run-off).
Mike Titchener from Stormwater360 says the right mix of low organic and high inorganic planting medium, and at least three months of intensive care before the roof is installed, means there are no weeds and no dying plants in the hot, wet and dry micro-climates on a roof.
The company has numerous New Zealand native or sedum planting options. A showpiece for the technology is the Tuhoe’s Te Uru Taumatua, a registered Living Building Challenge, where the modular roof ensures clean water enters the storm water system (and there is up to 80 per cent less run-off).
Green roofs are not just for rural settings. The roof of the international award-winning Forest Lodge Eco House by
Code Green is in the heart of the Sydney. The green roof was installed on top of structural steel crossbeams and a concrete roof, braced against the neighbouring heritage buildings. Plants were tested off-site to ensure they needed no human support to survive. There is also an 8-metre-high vertical garden. Both gardens are fed by underground water storage tanks.
Code Green is in the heart of the Sydney. The green roof was installed on top of structural steel crossbeams and a concrete roof, braced against the neighbouring heritage buildings. Plants were tested off-site to ensure they needed no human support to survive. There is also an 8-metre-high vertical garden. Both gardens are fed by underground water storage tanks.
In a tight urban site in Maryland, American architects Meditch Murphy wanted to bring the outside indoors, and the owners wanted to be able to live on the roof, nestled into a canopy of mature trees of the surrounding neighbourhood.
They engineered the roof to carry planters large enough to support 6-metre-high trees and deep enough soil to grow a vegetable garden. The roof also carries a solar array and provides super-insulation to the house below.
In coastal California, Studio Schicketanz used a green roof to conceal this home from neighbours above it. The building shelf was cut into the grassland and the uphill land extended as a green roof over the underground parts. The gently curved roof is the living room. The system is supported by a 19,000-litre underground water tank.
And in Denmark, the ultimate in green roofs can be seen on this summer cottage by Kassow Arkitekter. Roofs planted with the same tussock as the surrounding paddocks blend the house beautifully into its landscape.
TELL US
Are you ready for a green roof system on your new build? Share your ideas in the Comments.
MORE
10 Reasons to Love a Green Roof
6 Australian Dwellings that have Gone Green on Top
Understanding Flat Roof Construction
TELL US
Are you ready for a green roof system on your new build? Share your ideas in the Comments.
MORE
10 Reasons to Love a Green Roof
6 Australian Dwellings that have Gone Green on Top
Understanding Flat Roof Construction
But for houses, what are known as extensive green roofs generally need a substrate of only 20-150 millimetres, and are cheaper to install because they don’t need as much engineering support. This Muriwai beach house shows the most common planting: hardy grasses can survive in a shallow substrate with very little maintenance or irrigation.