Effective green building means wringing multiple benefits from building elements and products. Green roofs – with their ability to affect stormwater run-off, in-house energy use and even city pollution levels, and their range of relevance from single dwelling houses to suburbs and city blocks – bring a lot of multi-tasking capacity to the planning table.

A green roof describes, in essence, a layer of planting medium and vegetation covering an impervious roof surface. As a retrofit, a green roof can involve lightweight modular plant-holding components installed over an existing sealed roof. A non-trafficable green roof with 100–300 millimetres of growing medium and little to no irrigation is known as an extensive or semi-extensive green roof. In a new building, a green roof can range from a lightweight modular system to a deeper engineered soil bed on a membrane, right through to the intricately designed 150-millimetre-deep hills and dales of Renzo Piano’s California Academy of Sciences building (above) in San Francisco. A trafficable landscape, with a media depth of 200 millimetres or more and an in-built irrigation system, is known as an intensive green roof. Some of the benefits a green roof brings to a building and to the greater townscape are:

• Water Depending on the depth of soil and vegetation chosen, a green roof can retain up to 90 per cent of stormwater run-off, making it an effective water bank particularly useful in cities with combined sewerage/stormwater systems. Combined with a smaller-scale rainwater-harvesting tank, a green roof makes it a relatively simple task to harvest 100 per cent of a roof’s run-off. In addition, a green roof can filter roof water and can even be engineered to filter the greywater for reuse.
• Urban heat mitigation A 2007 thermal-imaging exercise in Chicago revealed the heat of two adjacent buildings: one black-roofed structure measured 40 degrees Celsius, while the City Hall’s green roof registered 21 degrees Celsius. Chicago and, more recently, the city of Toronto are actively championing the green roof as a way to reduce the urban heat-island effect and the associated issues of high pollution and increased energy use for cooling buildings.
• Carbon sinks In addition to the reduction of pollution through reducing city heat, the types of plants used on a green roof can increase the reduction of CO2 in the air. C4 plants are generally hardy, water efficient and soak up a greater amount of CO2 than trees, which can lose up to 40 per cent of the CO2 fixed in photosynthesis through photorespiration. Australian native C4 plants include black speargrass (Heteropogon contortus) and kangaroo grass (Themeda triandra).
• Energy saving and noise reduction The thermal mass combination of soil and captured water is an effective way to keep a building cool and quiet. Green-roof manufacturers claim a noise reduction as high as 40 decibels; another incentive for the commercial adoption of green-roof systems.

  In addition to the heating and cooling savings inside the building envelope, mounting solar panels over a shade-tolerant green roof can increase the efficiency of the photovoltaic cell (PV) panels by up to 30 per cent.

• Green can be beautiful From habitat re-creation and assisting biodiversity, to the practical benefits of ‘sky farming’ and the emotional satisfaction of a beautiful landscape, a green roof delivers valuable real estate to a building. Best of all, designing and creating a green roof can be as simple or complex as you make it.

Recently completed by Peter Elliott Architecture + Urban Design, the water recycling plant at Melbourne Zoo solves PTW and Arup’s new inflatable WaterCube pool structure in Beijing is inspired by frothy water and informed by the structure of bubbles. Of similar facetted and useful geometry is the much-exhibited JellyFish House concept by US firm Iwamotoscott. Multitasking structure – in particular walls – is becoming a theme in conceptual architecture and the JellyFish House demonstrates a hard working, “mutable, layered skin” structure which has poetic as well as functional effect.

The Iwamotoscott approach to site and house is one of cleansing and filtration: the site of contaminated landfill is purged with a series of proposed wetlands, while the geometrically structured skin of the house is used to direct and contain rainwater, and also to purify it using UV light. Like its namesake, the JellyFish House co-exists with its environment, using its layered and baffled, water-filled skin to mediate external and internal environments. The use of titanium dioxide coatings on the faceted water collectors to filter the unwanted UV rays means that the house skin glows blue as it filters.

The Clovelly House by Kennedy Associates is less phosphorous in flagging its filtration process, but no less visual. A verdant vertical wall of planted water channels filters greywater for reuse within the small suburban site.

Water purification and vegetation combine in a completely different way in the Seawater Greenhouses growing lush greenhouse plants in seaside and desert locations worldwide. Using seawater to cool and humidify the air for venting, and harnessing sunlight to distill the salt water to fresh, the Seawater Greenhouse design reinvents desalination as a sustainable process.

In collaboration with architects Nicholas Grimshaw & Partners, the Seawater Greenhouse concept has been expanded into a theatre building which uses solar energy to distill seawater from its Canary Island site to irrigate the adjacent gardens.

Melbourne Zoo Water Recycling

Recently completed by Peter Elliott Architecture + Urban Design, the water recycling plant at Melbourne Zoo solves a long-term waste water discharge problem. The entire stormwater drainage system at the zoo, including animal wash down areas, converges at one discharge point at the northern end of the site where a newly constructed weir diverts dry-weather run-off and first-flush wet weather flows to the water recycling plant. The water is then stored in two underground concrete holding tanks – one 750kl raw-water tank and one 145kl treated water tank. The harvested water is recycled to class 3A1 quality by reverse osmosis and then re-used in the zoo’s ponds, animal hose-down areas and landscape irrigation. The treatment plant is the end point of an interactive water discovery exhibit woven through the Zoo.

Water Wheels

Water wheels were the first recorded use of water for generating power. Giant fish shaped tails won’t be the last, but they are an exciting development for renewable, ethical power generation. With over half the world’s renewable energy derived from water, water-based energy options are surfacing in all areas of industry. Just a few fish in the sea: bio-morphic wave and tidal power solutions, zero carbon desalination, harnessing the r value of H2O for thermal comfort, and the big one, hydrogen power for cars, houses and industry, emitting nothing but pure water.

Pininfarina’s Sintesi

Shown in geneva this year Pininfarina’s Sintesi concept features “Liquid Packaging” where the traditionally heavy, unwieldy hydrogen fuel cells are split up with four motors and positioned low around each wheels for better interior packaging and general weight distribution. other cars such as hondas FCx Clarity are hydrogen-ready to roll but with nowhere near the Sintesi’s charisma.

Aquaduct

Tootling along under pedal power, the rider of the aquaduct is transporting, filtering and then storing water for potable use courtesy of a pleasantly fluid design, a carbon filter and a pump attached to the pedal. The clean tank on the handlebar is removable.

From artificial reefs spawning new life, to sunken follies for the sake of submerging people to the seabed.

While buildings struggle to stay on top of rising water, there is plentiful evidence to suggest that letting them sink can be beneficial. Land- bound buildings have a history of utilising the thermal properties of water to increase human comfort, with techniques ranging from the positioning of vessels of water within a structure for thermal mass, to wrapping vertical structures around sunken ponds to generate thermal currents for natural ventilation.

It seems logical that floating houses would bed some of their rooms into their surrounding water to harness the mass of the ocean. A handy side effect would probably be an increase in fish numbers surrounding the structure. Ongoing US surveys have found fish densities are 20 to 50 times higher at artificial submerged oil platforms than in surrounding open water.

The high fish statistics on offshore oil rigs have spawned the US Government-led Rigs to Reefs program where decommissioned rigs are sunk to form artificial reefs. With more than 100 rigs made obsolete each year in the Gulf of Mexico alone, that’s a fair chunk of new reef. Closer to shore, disused train carriages and old tyres are commonly concrete-booted and dropped overboard.

Osbourne Reef, a tyre dump reef in Florida, demonstrates the downside of tyre dumping: In storms during the 1990s the submerged tyres broke free and rolled uphill, flattening a natural reef nearby. In Qatar ‘reef balls’ of cement and silica mimicking natural reef limestone are deployed in their hundreds to strengthen natural reefs. In a joint reef-building effort, Israel and Jordan are using Ocean Bricks, an architectural modular reef-building invention, to take pressure off the over-dived natural reefs of the Red Sea. Installed mid-2007, the fledgling reef has already 32 species of fish; half the number normally found there.

Hydropolis, Dubai

The vision of architect Joachim Hauser, Hydropolis houses 220 suites within a ‘submarine leisure complex’ 20 metres down – where else but dubai? originally scheduled for completion in december 2007, now delayed until 2009, hauser’s design references symbols of man and nature, but is sadly not powered by tide currents or waves. hauser’s press has proposed the hotel will draw attention to the degradation of coral reefs, but declined to provide detail on how his proposed 260-hectare footprint would affect the seabed.

Jules’ Undersea Lodge, Key Largo, Florida

The “first and only underwater hotel” lets you “visit inner space and experience what was once just a dream of science fiction writers” (jul.com). The underwater lodge can only be accessed by scuba diving 6.4 metres down and entering the lodge from below. Photographs of the interior show a sadly conventional, caravan-like reality. the complex also houses marine research labs.