Buildings are expected to feature as a crucial area for energy-saving in the UN's third report on climate change this week.
By Patrick Jackson
Unido says Russian sand and seawater blocks fit like Lego
Encamped on the edge of London's docklands development, a bazaar of corporate stalls is pursuing the green pound in Britain's ever-hungry construction industry.
Production of concrete, that staple of modern building, alone accounts for up to 10% of man-made greenhouse gas, US scientists believe.
Then there is the energy spent on shipping the materials, and finally the power needs of the finished buildings.
Yet with a bit of clever substitution and sourcing, and some deft adjustments to the existing housing stock, environmentalists believe that CO2 emissions could be reduced anywhere in the world.
House of straw
If the number of "green" consultancy companies at London's Think 07 trade fair is anything to go by, environmentally-friendly architecture is becoming big business in the developed world.
Among the items on display are designer energy-saving bulbs and an ingenious-looking tube for piping daylight from your roof into your house's darker rooms.
Most tangible of all, at an event dedicated to the UK's property and construction industries, are the wood fibre and cement building-blocks stacked in one corner.
Sustainable rotation crops like hemp are the cost-effective future of building, according to Tom Woolley, a professor of architecture at Queen's University Belfast.
One hectare of land can produce enough hemp stalk to build a house, he told the BBC News website, and using about 12% of the UK's set-aside land, you could grow enough hemp to build the 200,000 new houses the country needs. Then you have the fibre and oil for other products.
He picks out the Eco Depot in York, a new city council building, as a good example of green architecture, pointing to the straw bale panels used for its walls and its "breathable" lime render.
Its "low-impact" design means the need for heating or cooling is minimal, he says.
With existing buildings, he believes that the crucial thing is to improve insulation, for example with a mixture of hemp and lime on old brick buildings, a technology used in France.
Solid sea and sand
Home to 80% of the world's population, the developing world has access to less than 20% of the world's construction materials, according to figures from the UN's industrial development agency (Unido).
Unido's technology promotion unit seeks out cheap, energy-efficient construction technology and introduces it to some of the poorest regions on Earth, suggesting novel ways of using local materials to cut the financial and environmental costs still further.
"The owners of the technologies often do not know how to market them while those looking for the technologies don't know where to find them," Vladimir Kozharnovich, the unit's programme manager, told the BBC News website.
"We seek to provide people with technological options which can be adapted to their specific environment."
In Herat, Unido has planned a model village of 100 energy-efficient homes, designed by Indian and Chinese architects in consultation with the local authorities.
The homes each cost a projected $3,500 and are equipped with bathroom, toilet and solar-powered electricity. Building costs are reckoned to be 30-50% cheaper than existing dwellings.
However, the plan is at a standstill while Unido awaits approval from the donor, Japan. Slow donor approval is a common problem, Mr Kozharnovich says, but already he is working on a new, similar Afghan project, this time for the province of Baghlan, with EU funding.
Unido promotes Indian portable brick factories as one answer to cheap construction materials. Another project, now under discussion with Namibia, is a Russian technique for manufacturing building blocks out of sand and seawater.
"The precision is very good - it's like Lego," says Mr Kozharnovich.
"It is a proven technology which cuts production costs five-fold, and can be used in both hot and cold regions."
One example of Unido's hi-tech thinking about sourcing local materials is in Botswana, where the agency has proposed melting locally available basalt as a replacement for expensive imported steel rods in concrete buildings.
Unido, Mr Kozharnovich stresses, does not seek to change local architecture, but to find more efficient ways of using local materials which will be acceptable locally.
It could, he says, mean a traditional timber frame with non-traditional wall panels made of wild grass.
Prof Woolley notes that unfired mud brick (adobe) technology has taken off in the US, dispensing with the energy used in firing traditional clay bricks.
Sun-dried bricks were a mainstay of construction among the indigenous peoples of the Americas for thousands of years, and go back centuries in Africa, an example of the return of a trusted old technology.
One modern trend Tom Woolley bemoans in the UK is what he says is over-emphasis on green energy creation.
"Somebody has very cleverly got the vast majority of politicians and the public to think that sustainable buildings is about sticking extremely expensive renewable energy equipment on the roof of the building, which is actually the last thing you should be doing," he says.
"The first thing is to reduce the demand and produce buildings which are breathable and well insulated and airtight."
The architecture professor admits that pioneering projects with organic materials can be expensive but confidently expects that the costs will fall once the new technologies go mainstream.
Tom Woolley's latest book, Natural Building, is out now.
SUSTAINABLE BUILDING: YORK ECO DEPOT
1. Solar panels: Photo-voltaic cells generate electricity
2. 'Brise soleil': Shades prevent sun hitting windows
3. Straw bale panels: Help insulate building
4. Lime render: More breathable and flexible
Source: City of York Council
I am an engineer, who designed my house, in humid Maryland USA, utilizing a unique flat roof, and roof spray system. On hot days, my roof is repeatedly wetted, and dries; it never gets hot. I estimate it is a 6 - 10 ton unit (zero at night), which costs circa ten cents per day. Roughly half of a house's heat load is due to the roof; most folks pay for air conditoning to fight it. My electric bill is roughly a third of similar homes. My cost penalty is heavy trusses to support winter snows, and slightly more water usage, roughly another washing machine load. The design paid for itself in one summer, thirteen years ago.
R. L. Hails Sr. P. E., Olney MD
Straw, after threshing, baled in wire and laid in brick courses on a bale-wide concrete foundation, with rebar every 16" through the bales. The bales are covered in wire netting and lime on the exterior and gypsum wallboard on conventional studs interior. The hay must be sealed off at windows and doors, and a wide overhang roof is best. Typical temperature under an R38 insulated roof is 54-58 degrees while outside temps swing from 34 to 80. The straw can be chemically fireproofed and is structurally sound to 24' structures. In earthquake zones, flying buttresses are inexpensive.
R. T. Marshall, Clyde, USA
Rammed earth in tyre walls building using old tyres as a recycled building material with a limecrete render. They built some in brighton but the concept originates in the US. The most ecologicaly sound buildings are ones that have recycled materials in the buildings.
Ben Irons, Warminster Wiltshire
I recently stayed in log cabins over Christmas in Northern Finland. The basis construction was of large pine (I think) logs. They were triple glazed and had underfloor heated tiles. The floor never felt excessively warm to touch, & although the outside temperature ranged from -8 to -20 celcius these cabins always felt comfortably warm. Perhaps Northern European countries should consider buildings of this design.
Chris Coomber, Leeds, West Yorkshire
We are just beginning construction of a straw bale home. The bales are locally grown and the foundation is ICF. Our roof is steel as this is the best for this climate. Many homes are being built of straw bales in BC and we have visited over a dozen in California and Washington.
All are owner built as proffessional builders are still uncertain about the proccess and therefore put their estimates up to where people are left with the "I'll do it myself" option.
We are hoping to finish construction through the winter of 07.
K Wells, Kamloops BC Canada
All this is very interesting, but I must admit to skepticism, at least in applying this green building technology to Western structures. If the "Lego blocks" used in Russia, for example, are so good why aren't other countries using the technique? Ditto for the other ideas presented. Do builders simply not realize these materials exist, are the materials expensive in the West, are they even available? Of course, the biggest question is do the greener construction materials hold up as well as the traditional materials. At first look, yes these are interesting and potentially valuable materials and techniques. I am pleased to see the York Eco Depot built. But to scale up to a nation-wide industry is a whole different matter.
Bob Zimmerman, Philadelphia PA USA
Sounds great but have you ever tried to buy hemp insulation? It costs five times more than glass or rock wool in spite of allegedly using less energy in manufacture. Delivery time is in months, even in the autumn after the harvest, though the factories chopping and spinning the hemp work all year round. It is a rip off for the gullible.
brian, France, Bordeaux
I don't think there is one technology that strikes me as being particalury promising on it's own but several which work togther well to offset our carbon and energy usage. Straw bale, green oak (or Douglas fir) and lime/clay rendering is a good example of this in house builds. All of these materials are widely accessible and available in the UK and have been used for centuries (straw thatch rather than bales) it's just the the building and supplies industry is geared to using high profit manmade materials.
David Waller, Gangor, Gwynedd
I can remember buildings going up 35 years ago that used cement bonded straw to produce fire retarding insulation boards. I have never seen it since and yet we see so much straw piled up into the the corner of fields and abandoned or used as no more than windbreaks for a field. Surely this is what we should be using for sustainable building - a low tech product using materials that have no other viable use. The cost of straw is minimal as it is an excessive by product of cereal production and it can be used to give very quick structures. It really would be a win in so many ways: cheap, quick, a highly insulated, cheap to run finished product and a way to rid the countryside of some eyesores - which would also free up more land to produce the raw material!
Jonathan Lodge, Slough, UK
Try and get a mortgage on a house built of hemp! The building society will laugh at you. Its virtually impossible to borrow against a wooden house never mind anything else.
In my existing house I use water evaporative coolers instead of air conditioning.
I intend to design my next house to use a minimum of energy. The key is to have a high thermal mass inside the house and to insulate the exterior. British houses with their brick interior walls are not a bad design. By contrast, American homes are the worst possible design; they have almost no thermal mass because the walls are little more than plasterboard, and consequently, heating or cooling must be run almost continuously to maintain a comfortable ambience in cold or hot weather.
Clive Warner, Monterrey, Mexico
Here in Australia solar energy is often used to heat water tanks, but even here with plenty of sunlight you rarely see photo-voltaic cells. They're very expensive compared to carbon-free alternatives like nuclear, and the manufacturing processes are very dirty.
Kestas Kuliukas, Perth, Australia
Zeolite or other pozzolanic volcanic materials can be used in cement to reduce the CO2 produced. This cement is just as good, if not better than regular cement and these materials are available in many places in the world. This "green" cement was known to the ancients, maybe we should be looking at this.
Liz Butler-Henderson, parson, b.c. canada
If council tax and house prices keep going up, a lot of people I know will be living under bridges and in bus shelters, which is quite low-impact in terms of new build and use of materials. Perhaps there's a cushy job for me somewhere, spinning the whole idea as a form of recycling?
I'm fascinated by straw bale houses. They hold heat well and stay cool as well and if covered in adobe or cement they do not rot. It is very interesting and intriguing.
Nicole, Caracas, Venezuela
In Africa and many other places people have made simple houses out of mud and straw and dung - in Devon they cost a mint and are a tourist attraction - cob and thatch houses! It is really very simple to use locally-sourced sustainable materials for house building - what is difficult is getting planning permission!
jo gibson, dawlish, devon
I've had the good fortune of living in an adobe house in Mexico several years ago and they are very, very good through a varied range of weather. They are comfortable, and seem easier and cheaper to maintain.
Donald London, Grand Junction, Colorado
I like rammed earth houses, but they do take quite a bit of energy to build- straw bale seems to me to be the way of the future.
jesse phelps, Oakland, CA USA
I deliver building materials all day long. I'd like to think that one day I'll be delivering sustainable technology such as that mentioned above. All we need now is a susatainable carbon neutral fuel for my truck when I'm driving it around.
Mike Stryk, bognor regis