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.

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.