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Is straw the building material of the future?

The Sheet — Tue, 20 Jul 2010 09:27:15 +0000

Straw houses could help to cut carbon emissions – and new research proves that they won't blow down

Building his house of straw didn't do the first little pig any favours, but a modern take on straw-bale construction may well be the grand design of the future if results coming out of the University of Bath are accepted by the construction industry.

Think of a straw-bale house and you might imagine a tumbledown shack that leaks, creaks, slumps and smells somewhat of the farmyard. But step into BaleHaus, a startlingly contemporary looking prototype home that has been built on the Bath campus, and there's nary a wisp of straw to be seen. Instead, you're in the hallway of an upside-down house with two bedrooms and a bathroom on the ground floor, and an airy open-plan living area upstairs. It feels like a little piece of Scandinavia has just arrived in Somerset.

The straw bales, it turns out, are all packed tightly inside a series of prefabricated rectangular wooden wall frames, which are then lime-rendered, dried and finally slotted together like giant Lego pieces, called ModCell panels.

The problem with straw houses, it seems, isn't that they don't work, but that people perceive them as being a bit hippy and not particularly durable. Add to that the problems of getting a mortgage – very few lenders will consider straw-bale construction – and it's hardly surprising that most homes in the UK are still built of either brick or stone.

The benefits of straw, points out Professor Peter Walker, director of the University of Bath's BRE Centre for Innovative Construction Materials, are that "it's cheap, widely available and a good insulator. It's been used in building houses for hundreds of years."

As a by-product of an industry that exists all over the world – the stalks that remain after grain has been harvested – straw also helpfully soaks up carbon from the atmosphere and locks it in, so long as it is not allowed to decompose. For the building industry, which currently depends on materials with very high embedded energy costs – concrete and brick are expensive in carbon terms both to make and to transport – straw could therefore offer a welcome solution to housing's greenhouse gas emissions.

However stylishly modern your environmentally friendly straw-bale house may look, however, you still want to know that it won't get sopping wet in a thunderstorm or go up in a whoosh of flames if you knock over a candle. The results now being published by Walker and his research partner, Dr Katharine Beadle, who have spent the last 18 months testing the BaleHaus against an exhaustive list of risk factors that could rot it, burn it or blow it down, so far seem to be reassuring.

"You always want a bit of drama, but we didn't get it!" laughs Beadle of the day the team took a ModCell unit to a test laboratory and tried to reduce it to ashes by strapping it to a fiery furnace and raising the temperature to over 1,000C.

"It's a standard test to replicate a fire in a building," explains Walker.

"You want a minimum of 30 minutes' resistance; that means you know that a house will at least retain its structural integrity for half an hour, which gives people a chance to get out."

It took an hour-and-a-half of being in direct contact with the flames, says Beadle, before the lime render began to drop off, "and then the straw did start to burn back, but because it's so compacted it suffered more charring than actual disintegration."

After waiting another 45 minutes and finding that the panel still hadn't failed, the team gave up and stopped the experiment, secure in the knowledge that the material had performed way beyond the requirements of building regulations.

When it came to blowing the house down – hydraulic jacks were placed against the walls to replicate wind forces pushing against the bales – the ModCell panels moved a few millimetres, but stayed within the tolerances allowed for by the computer modelling carried out prior to its construction.

That, says Walker, could be very good news for the price of the eventual ModCell building system.

"It means the house is stiffer than it needs to be, so we now have the option of taking away some of that stiffness – ie, reduce its internal timber – and that could reduce the cost."

The approximate cost of the current modular building system for this design is £132,000 from above the concrete slab. For a smallish two-bedroomed house with one large open-plan kitchen/diner, that doesn't seem particularly cheap given that straw is supposed to be inexpensive, and you'd still have to buy the plot and dig the foundations.

"Cost is a challenge to the introduction of this technology, but as a prototype house I think it stacks up well," says Walker.

"The aspiration is that it should be cost-competitive, with more savings coming through reduced heating bills."

To replicate the heat given off by humans and appliances, arrays of incandescent lightbulbs on timers blaze in every room at pre-programmed times of day "to see how much heat escapes, and what level of heating would be needed at different times of year," explains Beadle.

"That environmental modelling will give us all the numbers about the energy the house is predicted to use. And if we are predicting how it will operate given climate change, we can then put in those variables."

Sensors embedded within each wall panel constantly monitor the degree of moisture absorbed and then released back through the breathable lime render into the air outside by the panels. And on the airtightness test that was carried out, BaleHaus came in way under the building regulations threshold, and did considerably better than the far lower "best practice" standard.

Next up is going to be the flood test. Disappointingly, the researchers aren't simply going to leave the bath taps running: instead, they'll stand a panel in a metre of water, measure how long it takes to dry out and assess whether using industrial dryers causes damage to the straw.

"Longer term, we'd like to maybe get some people to live in it, a family of three or four perhaps, and see how it performs in a real-life situation," says Walker.

Student accommodation, I wonder? Walker suddenly looks a bit concerned for his straw-bale baby, so probably only mature, well-behaved responsible students who will promise no rampaging house parties should apply. But who knows when the first straw-bale halls of residence will be built for students desperate for some decent, earth-friendly and thermally efficient digs?bre

Louise Tickle

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Video: Inside Europe’s largest biomedical research institute, the UKCMRI

The Sheet — Sat, 19 Jun 2010 08:23:53 +0000

Artist's impressions of the planned UK Centre for Medical Research and Innovation (UKCMRI) behind St Pancras in London

Notes and queries: Why is Doctor Who always a Time Lord and not a Lady?

The Sheet — Mon, 08 Mar 2010 10:55:35 +0000

Why is Doctor Who always a Time Lord and not a Lady? Journeys to the centre of the Earth; The meaning of a hiding to nothing

Why is Doctor Who always regenerated as a Time Lord, not a Time Lady?

In Doctor Who the process of regeneration is the renewing of every cell in a Time Lord's dying, damaged or unwanted body. Since Time Lords (and Time Ladies, and perhaps even Time Tots, as the children of Gallifrey are known) can change species when they regenerate, there is presumably no reason why they can't also swap sex. There's certainly nothing in the TV series' history to contradict this theory and indeed no way of telling whether the Master, the Doctor's sworn enemy, spent one or more of his 13 wasted lives as a femme fatale called the Mistress.

Kieran Grant, London N22

Time Lords can be male or female. One of Tom Baker's companions was actually a female Time Lord called Romana who regenerated between seasons and I also understand that one of his recurring enemies was another female of the species called The Rani.

Apparently, the only way a Time Lord can regenerate as a member of the opposite sex is to commit suicide. This has happened at least once to my knowledge, in a Doctor Who Unbound audiobook called Exile, where he commits suicide and becomes Arabella Weir in order to hide from pursuers.

Guy Thomas, Canterbury

Why the Doctor has never managed to exchange his Y chromosome for a second X is one of the universe's great unsolved mysteries. Had he managed to do so, we might have been fortunate enough to experience the doctorly delights of the likes of Honor Blackman, Judi Dench, Sheila Hancock, Maggie Smith or Kathy Burke. Whatever the reasons for such rigid gender typecasting, lack of available talent isn't one of them.

Sheila Kirby, Esbjerg V, Denmark

The world's tallest building is the 828m Burj Dubai, but what is the world's deepest man-made structure?

Various mines and deep geological repositories for nuclear waste approach one kilometre. At 24.5km, Norway's Laerdal tunnel is the longest road tunnel in the world, and also up to 1400 metres deep. However, the record for the deepest hole is held by the Russians, who started drilling the Kola Superdeep Borehole in 1970 and reached the depth of 12,261 metres in 1989. The purpose of this hole is to study the continental crust. However, this represents only about 0.2% of the journey to the centre of the Earth.

In a tongue-in-cheek paper published in the science journal Nature, David Stevenson, professor of planetary science at Caltech, explains how a grapefruit-sized unmanned probe could reach the centre of the earth in a week or so. The first step would be to detonate a nuclear bomb to generate a crack in the Earth's crust 30cm wide and several hundred metres long and deep. Molten iron containing the probe would need to be poured into the crack the instant it formed. Being denser, the iron would sink, which would lead to the release of gravitational potential energy, melting the underlying rock. Once the glob of iron had passed, the rock would close up again. Data would be sent to the surface as vibrations. But the £6.5bn price tag means it will not be happening any time soon.

Mike Follows, Willenhall, W Midlands

"A hiding to nothing" – I know what it implies but it doesn't make sense. Can anyone explain?

It refers to a situation where one has everything to lose and nothing to gain. It is used (often in football) to describe a contest against supposedly inferior opposition where winning would be expected and produce little credit, while losing would be a calamity. The hiding refers not so much to the other team's performance but to the public outcry and humiliation.

The meaning of "hiding" is from the association of corporal punishment with the tanning of skins. Hence, "I'll tan your hide" and "give you a good hiding". So winning the uneven contest would be "nothing", while losing would be a "hiding".

Martin Skinner, Leamington Spa, Warks

Why are there no female Formula One drivers?

Due to their ancestors' roles as (respectively) hunters and nurturers, men's and women's brains evolved different pathways to help them make decisions. Women specialised in more nuanced, longer-term decisions, while men learned how to make good instant decisions. It's a bit of a generalisation, and there are obviously exceptions – the female Red Arrow, for instance, and the men who work in caring professions – but together with their numerical advantage, it explains why men become (and want to become) racing drivers and fighter pilots.

Nick Marsh, Sutton-at-Hone, Kent

Any answers

In folklore werewolves look like real wolves. That's the whole point – you don't know which is real and which is supernatural until it's too late. So why in films and TV do they look like very hairy people?

Susan Deal, Sheffield

What is the origin of the mortarboard as an item of academic dress? Why is it worn by graduates at some universities but not at others?

Lilian Dunlop, Manchester

Send questions and answers to nq@guardian.co.uk. Please include name, address and phone number.

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Golden ratio shows maths and art come from the same place in our minds

The Sheet — Mon, 28 Dec 2009 15:33:31 +0000

The beauty of the golden ratio, surely, lies in the discovery of harmony in imbalance – that is, it's not a symmetrical division, it's not 1+1, but a bit more interesting and lively. In architecture, the piers and windows of Durham Cathedral seem to apply it as assiduously as in the Parthenon in Athens. But why such mystique?

The ancient Greek thinker Pythagoras was moved to find that a string only produces perfect musical notes when divided by exact mathematical fractions. He saw this as a revelation of divine beauty. This attitude to number (that it is the key to the secret harmony of the universe) survived in the middle ages in Muslim and Christian architecture.

In the Renaissance, Leonardo da Vinci took it to new extremes, analysing the perfect proportions of a horse and a human and finding number at the heart of nature. In 1504 he was designing fortifications for an Italian town. While researching this for a forthcoming book, I puzzled over diagrams of pyramids that keep interrupting plans for towers – until I understood that Leonardo believed so passionately in the power of proportion that he thought it could make a castle invulnerable. He illustrated his friend Fra Luca Pacioli's book The Divine Proportion, which praises the golden ratio, and so helped to create one of the most persistent cults in maths and art.

Whether or not the golden ratio really has any special significance in human psychology, it has been given that status by artists like Leonardo. Another is surely the great 15th-century painter Piero della Francesca, whose geometrically pleasing art is rooted in mathematics. The persistent pursuit of this proportion right down to Le Corbusier proves that mathematics and art come from the same beautiful place in our minds.

So how do you find this special proportion? Divide a straight line in two so that the ratio of the whole length to the larger part is the same as the ratio of the larger part to the smaller part. The result (roughly 1.62 to 1) is the golden ratio.

Jonathan Jones's book about Leonardo da Vinci will be published by Simon and Schuster in April 2010.

Jonathan Jones

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Science Weekly podcast: Solar activity and global warming, plus ‘female viagra’

The Sheet — Mon, 23 Nov 2009 11:49:39 +0000

Astronomer Stuart Clark joins us in the studio to look at the latest thinking about the effects of variations in solar activity on the Earth's climate. Dark matter gets a mention too.

Over the coming days he will be conducting question-and-answer sessions on Twitter - both on solar activity and dark matter. Follow him at DrStuClark and post your questions using the prefix #AskDrStu. (2:00)

There's a new BBC TV series starting this week called Paradox. Its writer Lizzy Mickery comes into the studio to tell us about the challenges of getting a drama based on science onto prime-time TV. (12:10)

In the newsjam we look at a new drug hailed as the "female viagra" and Nasa's announcement that its LCROSS probe found water on the moon. (15:30)

Duncan Clark from environmentguardian.co.uk responds to the s*** storm of blog comments arising from last week's podcast on eco-myths. Who'd have thought people could get so excited about nappies? (23:25)

Steven Levitt talks about his controversial views on geo-engineering, expressed in his latest book SuperFreakonomics. Hear more of that interview in the Guardian's The Business podcast. (26:15)

All the way from Denmark, Dr Rachel Armstrong discusses living buildings and metabolic materials. She is giving a Lunch Hour Lecture at UCL this week. (30:15)

We finish the show with more music ... the winner of Discover Magazine's "evolution in two minutes or less" video competition. (33:15)

Science correspondent Ian Sample lends us his wisdom in the pod. We promise to give it back soon.

WARNING: contains strong language.

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Makeover may lose Andean pyramid its world heritage site listing

The Sheet — Tue, 20 Oct 2009 09:01:04 +0000

Renovations to attract tourists to Akapana pyramid may end in building being removed from UN list of archaeological treasures

As with all makeovers, it seemed a good idea at the time. The village of Tiwanaku in the Bolivian Andes reckoned it could attract more tourists by giving an ancient pyramid a facelift.

Workers plastered the Akapana pyramid – one of the biggest constructions in South America which predates the Incas – with adobe to make it look more impressive.

The problem, according to some experts, is that the new look is an archaeological travesty which could cost the pyramid its UN world heritage site designation.

Rather than clay bricks, the original construction, of immense spiritual significance for the Tiwanaku civilisation, is believed to have used stone.

"They decided to go free-hand with the design. There are no studies showing that the walls really looked like this," José Luis Paz, who has been appointed to assess damage at the site, told Reuters.

Officials from the UN heritage agency, Unesco, are due to visit Tiwanaku to determine if its main attraction should be removed from the list of world archaeological treasures.

It was included in 2000 because its ruins "bear striking witness to the power of the empire that played a leading role in the development of the Andean pre-Hispanic civilisation". The Tiwanaku civilisation, which reached Bolivia and parts of Peru, Argentina and Chile, existed from 1500BC to AD1200. The pyramid was thought to have been built between AD300-700 .

Paz, who heads excavations at the site, said the adobe not only looked wrong, its weight risked collapsing the pyramid. Thousands of tourists pay $10 (£6.50) each to visit every year and the people of Tiwanaku, he said, hoped to swell the revenue with a "more attractive" structure. Staff from the state National Archaeology Union (UNAR) did the renovation.

The motivation may have come from guides such as the Lonely Planet which noted the original Akapana pyramid, ransacked and eroded, "was in a rather sorry state".

Authorities defended the renovation. "The UNAR has restored the original form the pyramid had," the culture minister, Pablo Groux, told Reuters. "If we look at pictures from five years ago, there was just a hill there. What we can see now is something close to what the construction originally looked like."

He said Tiwanaku would not lose its world heritage status because the government halted the makeover earlier this year when told to do so by Unesco.

"The inclusion in the list of world heritage sites involves regular checks, because some places may lose the essence of why they were included in the list. In the case of Tiwanaku losing that title is unlikely," he said.

Rory Carroll

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