Hemp Eco-Building futures in the FT

Mark Barrett marknbarrett at googlemail.com
Mon Jan 25 16:33:22 GMT 2010

Green Party Policy: 'DU405. Cannabis would be removed from the 1971 Misuse of drugs act. The possession, trade and cultivation of cannabis would be immediately decriminalised...'

Construction plant

By Paul Miles
Published: January 22 2010 23:16 | Last updated: January 22 2010 23:16

“Some devotees think it’s the answer to everything,” says Pete Walker of hemp. “You can eat it [it is rich in omega-3 and omega-6 oils], use it as body lotion, wear it, write on it – and, of course, smoke it – but our interest is in building with it.”

The director of the UK’S Building Research Establishment Centre for Innovative Construction Materials at the University of Bath recently started a £740,000 project, funded by the UK government and the construction industry, to study and develop the material’s use in building. The research builds on foundations laid more than a thousand years ago. Archaeologists in France have discovered a sixth-century bridge where the stones are held together with hemp mortar.

Cultivated for thousands of years for its fibres, which are used to make ropes and textiles, hemp, otherwise known as Cannabis sativa, was so important to the economy during King Henry VIII’s reign that farmers had to grow at least a quarter of an acre or risk a fine. In the latter decades of the 20th century production slumped as cotton cloth and man-made fabrics became prominent but in the 21st century hemp’s reputation is being rebuilt, partly thanks to properties that make it an ideal building fabric for homes.

Today, industrial hemp (a strain of cannabis that has almost no narcotic quality) is being processed into an environmentally friendly construction material that is then mixed with a lime binder to make a material that can be poured and cast like concrete or formed into bricks.

Hemp’s environmental credentials are many: it needs little or no pesticide or herbicide to grow. Its impact on food production is mitigated by the fact that it is the second-fastest growing agricultural crop in the world (after bamboo), maturing from seed to harvest in four months. Therefore, food crops can still be cultivated for two-thirds of the year and they will have the advantage of growing in soil that has been improved by hemp’s nutrient-enhancing actions.

Hemp does not take up much surface area – one hectare provides enough material to build one house. “All the 180,000 new-build homes the UK government ambitiously estimates are needed each year could be built with hemp grown on just 1 per cent of Britain’s agricultural land,” says Walker. (Last year, 5,000 hectares were grown in the UK – mostly for the fibre, which is used in the car industry.) Of course, hemp could also be used in the renovation of the millions of empty houses in the world. In terms of carbon emissions, hemp certainly trumps ubiquitous cement and concrete, the production of which causes between 5 and 10 per cent of global carbon emissions, says Walker.

Indeed, hemp construction can, theoretically, result in a building with zero carbon emissions or one that contributes to the eco-crusade by storing carbon dioxide. The plant – like all plants – absorbs the gas during its growth. Walker estimates that a square metre of a 300mm-thick hemp/lime wall stores about 33kg of carbon dioxide. By contrast, the manufacture of the materials that go into a square metre of standard cavity masonry wall is responsible for 100kg of emissions.

As global concern about carbon emissions leads governments to legislate for low carbon housing (the UK aims for all new-builds to be zero carbon by 2016), hemp’s use in construction is growing.

In France, where its revival began a few decades ago, there are several thousand hemp houses. In the UK, over the past two years a few hundred properties have been built, including a 4,400 sq metre warehouse with a living roof for the Adnams brewery in Suffolk, eastern England. Constructed from 90,000 hemp/lime blocks with hemp/lime cavity insulation, all made from locally sourced crops, it is the largest hemp building in the world.

The company estimates that there is the equivalent of 100-150 tonnes of carbon dioxide locked up within its walls while a conventional brick building of the same size would have been responsible for about 300 to 600 tonnes of CO2 emissions.

As well as the possibility of being carbon negative in construction, hemp has many characteristics that mean buildings will have low – or zero – emissions during use. Unlike most lightweight building materials, such as wood, it has a high thermal mass, meaning that it stores heat from the sun and releases it slowly during the cool of the night.

It is also breathable while being airtight, is good for soundproofing and is hygroscopic, meaning it moderates humidity. No wonder that Walker boasts that hemp provides “one of the most credible and novel uses of renewable crop materials in construction. It offers benefits for the agriculture and construction industries, occupant health and for wider society through the delivery of lower carbon buildings.”

Its proponents are keen to point out that hemp/lime is ideally suitable for domestic uses too. “You can build a very conventional house with it,” says Ian Pritchett, chairman of building products company Lime Technology. “It doesn’t have to look wacky.” He shows me round a very pleasant but ordinary-looking demonstration house the company has built in Watford, north of London, at the Building Research Establishment. Significantly, the company has changed its name from The Hemp House to The Renewable House.

Pritchett denies that this is to avoid some of the negative connotations people still associate with the cannabis plant. “The name-change reflects the nature of some of the other materials used in construction – mostly sustainably harvested natural products such as Scandinavian pine and sheep’s wool.” The three-bedroom house, which took just 15 weeks to build and cost £75,000, has exterior walls that have been smoothly rendered and painted. You would never guess that they are constructed from a plant most commonly associated in the public mind with a kind of joint not found in a building skills manual.

The house has so impressed the UK government that in November last year the Department of Energy and Climate Change, in partnership with the Homes and Communities Agency, announced that £5m of grant funding would be available for developers that build affordable homes from renewable materials such as hemp. After years of being associated with a hippy ethos and despite the potential for jokes, it appears that there is now good reason to take Cannabis sativa seriously.

    Shiv, the inner woody core of the hemp plant
    From bedding to building

    The inner woody core of the hemp plant, the “waste” by-product of fibre extraction, is used in construction. Until recently the most common use for these stalks, also known as “shiv”, was as horse bedding.

    In effect, the hemp replaces the aggregate – stones and pebbles – that are usually mixed with cement to form concrete. (One of the leading companies involved in hemp building, Lime Technology, calls its product “hemcrete”.)

    By varying the quantities of shiv to lime, different preparations can be made that are either cast or sprayed into a frame or formed into structural blocks. Curved walls can be formed as, being a fairly dry material, the hemp/lime mix can be shaped in lightweight, flexible shuttering.

    The hardened, finished material, which looks a little like baked mud full of flecks of straw, can be rendered with a layer of lime plaster or left untreated for a rustic look. 


DU100 Throughout history, psychoactive substances have been used by all societies and are likely to continue to be used in one form or another. The extent to which people use drugs depends not only on the availability of such substances but also on social, economic and environmental factors.

DU101 Drug use - whether experimental, recreational or dependent - can have a damaging effect not only on the user but also on the user's family and friends. The illegal drugs market is also having an increasingly harmful effect on society at large, mainly because of two problems: crime and HIV. Powerful criminal organisations are involved in the drugs market and a significant proportion of acquisitive crime is committed by dependent drug users to fund drug use. Shared drug use by injection is currently a significant transmission route for HIV, a major threat to public health.

DU102 In recent years, the `drugs problem' has been largely equated with the use of illegal drugs. This has had the effect of diverting attention away from the dire social and health consequences of legal drugs, principally alcohol, tobacco and inappropriately prescribed tranquillisers. Between them, these cause the loss of thousands of lives every year and much pain and disability for both users and non-users of these drugs.

DU103 The legal drugs, principally tobacco, alcohol and pharmaceutical drugs, are widely promoted through advertising, sponsorship and corporate pressure. As a result their use is generally accepted by society and efforts to control usage largely rely on a mixture of taxation, education, restriction of sale and use to adults or certain places, and voluntary restraint.

DU104 Under prohibition, illegal drugs are made not only more attractive to some, but also tend to be more poisonous and expensive. Consequently users become unhealthier and more likely to steal and deal. The cost of enforcing prohibition is becoming increasingly untenable.

DU105 Raves / pay-parties / free-festivals and the like have proved an enduring setting in which various drugs are consumed by many tens of thousands of young people across the country. Unlicensed and unregulated events, kept underground by prohibition, are held regularly in overcrowded venues or inappropriate sites that fail to meet health and fire regulations, at which ventilation and provision for refreshments are inadequate and to which the emergency services would be unable to gain access if needed. The popularity of these events and their proliferation in spite of attempts to suppress them makes the adoption of a more liberal approach coupled with a system of regulation a matter of highest urgency.

DU106 Small scale farmers in the underdeveloped South often rely heavily on the hard currency they can receive from drug crop harvests. Strategies by rich, drug-importing nations to eradicate drug crops, such as cash compensation, have proved woefully inadequate and are usually jeopardised by corrupt bureaucracies. Crop substitution has repeatedly failed because of depressed commodity prices for the underdeveloped world's exports.

DU200 Government responses to the issue of drug use are inconsistent: neither the legal status of different substances nor the targeting of government expenditure on the information / education is commensurate with the harm different drugs do to the individual or society.

DU201 Prohibition does not prevent drug use by adults or children and leads to the creation of an illicit market, an increase in consumption due to pyramid selling and the criminalisation and marginalisation of those who use drugs. Prohibition is counter-productive; it is more damaging to the drug user, the community and society than the drug use it seeks to eliminate.

DU202 Social custom, convention and ritual play a vital part in the moderate and responsible use of all drugs. The development and perpetuation of these customs are inhibited and eroded by prohibition and to some extent, by all interventions by government or state agencies.

DU203 The Green Party therefore seeks to open up the whole issue of drug use to the public and regards the supply of adequate, clear, free and accessible information as vital to the process of both reducing drug-use and minimising harm from drug use.

DU204 Interventions by importing nations, such as support for international drug-crop eradication and crop substitution programmes are both economically unfeasible and ecologically damaging. Measures such as increased military aid for repressive regimes against drug cultivation, as well as being morally indefensible, run the risk of fuelling political destabilisation.

DU205 In addition to instances of direct complicity in international drug traffic by agencies of importing nations, there is also an element of hypocrisy in the fact that whilst campaigns against drugs are being waged, rich nations are simultaneously trying to swamp many poorer countries' markets with the products of their own tobacco, alcohol and pharmaceutical industries.

DU300 In keeping with the Green Party's health promotion policies, the Green Party would aim to minimise the misuse of drugs.

DU301 At the same time, we recognise that drug use will never be entirely eliminated. Our policies would aim therefore to minimise the social, psychological and physical harm to those who use drugs and to society at large.

DU302 Green policies on drugs will be directed towards accepting the reality of drug use and will strive to minimise harm, both to the user and to society at large. This will require a more pragmatic approach to the issue of recreational and cultural use and should highlight the broader socio-economic forces which drive people towards escapist use.

DU400 Tobacco smoking is the principal cause of premature death in the United Kingdom. In view of the considerable dangers to the health of both smoker and non-smoker, the Green Party supports legislation prohibiting smoking in all enclosed premises to which the public has access.

DU401 The Green Party would also introduce a complete ban on the promotion of tobacco and alcohol products, including sponsorship, advertising (direct or indirect) and product placement on remuneration or reward. This ban would also apply to any currently illegal drugs when a policy of decriminalisation or legalisation comes into effect.

DU402 The effect on consumption of taxation on the sale of tobacco and alcohol would be subject to continued review and, where appropriate, these legal drugs would be taxed at a higher rate than at present. In addition, both the net profits of tobacco companies and companies producing alcohol for consumption, and the dividends paid to shareholders of these companies would attract a significantly higher rate of taxation than at present. The tax levied on alcohol products would be in proportion to the amount of alcohol in the finished product.

DU403 To facilitate the responsible drinking of alcohol by both adults and young people, the Green Party would encourage the option of serving alcohol in smaller measures and require suppliers to provide accurate information about the unit alcohol content.

DU404 Penalties for driving whilst under the influence of alcohol or other drugs likely to adversely affect the ability to drive would be increased and the permitted alcohol to blood ratio of drivers would be reduced. (see TR302)

DU405 Cannabis would be removed from the 1971 Misuse of drugs act. The possession, trade and cultivation of cannabis would be immediately decriminalised, roughly following the Dutch model. The trade in Cannabis would be the subject of a Royal Commission (see below), with a view to establishing a fully legalised, controlled and regulated trade. Small-scale possession of drugs for personal use would be decriminalised. The starting point would be advice to policing authorities to caution rather than prosecute for offences of drug possession for personal use and to refer offenders to the health-care services (see DU411). Subsequently, regulations would be brought forward removing criminal sanctions for simple possession of controlled drugs for personal use. The recommended sentences for small-scale supply would be non-custodial options. The possession of pipes made for the use in connection with smoking of opium would no longer be a criminal offence. A Royal Commission or similar body would be established to review currently controlled drug classifications, within a legalised environment of drug use. This commission would, after wide consultation, consider and recommend frameworks of social, economic and health conditions for drug use and supply.

DU406 With the exception of cannabis, Policing Authorities would be encouraged to focus detection resources on major drug trafficking operations. Unauthorised production, importation and marketing of all drugs controlled under the Misuse of Drugs Act (1971) would remain criminal offences. Fines, confiscation of assets and prison sentences would continue to be imposed for serious drugs trafficking offences.

DU407 A proportion of the fines and assets of convicted drug traffickers would be used to fund research into drug use and reducing drug related harm, to supplement the additional health services budget referred to below in 410-413 and resource the substitution of water-based glues, etc. in place of solvent-based products currently on the market.

DU408 The Green Party would seek to establish independent committees to oversee the structure of regulation for raves / pay parties / free festivals. These committees would ideally be made up of representatives of the promoters and attendees themselves, the local authority, the Police Authority and the Local Health Authority (LHA). The local authority would be responsible for ensuring that such events meet the necessary regulations and for issuing licenses. The Police Authority would have the responsibility for ensuring adequate coverage by emergency services and for training and regulation of 'bouncers' or others policing the event. The Local Health Authority would provide unbiased information and guidance on health and drug use in connection with such events. The Green party calls for the repeal of the Public Entertainment (drugs misuse) Act (The "Barry Legg act"), which is making outreach harm reduction measures impossible.

DU409 The Green Party would facilitate the establishment of a licensed non-statutory service providing analysis of any drug regardless of source. The service would be available for a small fee both to organisations and to members of the public and would be confidential, although statistical information from results would be published periodically.

DU410 General information and health education relating to all drugs, both legal and illegal, would be improved with separate approaches to three target groups: young people, those who use drugs and the general public. The Green Party would encourage counselling and advice on drugs to be available to everyone and especially to children and young people by the provision of non-statutory services in schools, youth projects, and via street outreach. These services would be free and confidential. (see H308)

DU411 The Green Party would provide an additional health service budget to fund an increase in the range and number of facilities, both residential and non-residential, for people with drug-related problems. Such facilities would be available on the NHS to all who needed them. Local government support for individually-inspired enterprises such as self-help groups would be encouraged.

DU412 In particular, each Local Health Authority would be provided with sufficient resources to establish appropriate drug-use clinics and needle exchange schemes and to ensure the provision of needle sterilisation facilities for use by prisoners. Related health programmes would also be resourced.

DU413 Resources, including greater support and training, would be made available to LHAs for certain medical practitioners to provide long-term (maintenance) prescriptions of drugs to people, including those in prison, who are unable or unwilling to stop, with the aim of reducing harmful consequences - including health and social problems (especially the spread of HIV and other blood-borne infections), pyramid selling and acquisitive crime. For this purpose, regulations would be brought forward ending, where appropriate, the prohibition on the prescribing and dispensing of certain drugs under the Misuse of Drugs Act. Evaluation would be a built-in component of this harm-minimisation strategy.

DU420 The Green Party would publicise the fact that as long as there are wide differences in living standards between the nations of the world, there will always be an incentive for the poorer countries to produce drug crops if a ready market exists for them in richer countries.

DU421 Support for international drug-crop eradication and substitution programmes would be ended.

DU422 Poor countries for whose economic survival the cultivation of drug crops (legal or illegal) is critical will be identified. The Green Party would launch a series of initiatives which would offer realistic alternative trading arrangements in more ecologically and socially benign commodities with the communities that are directly involved. Such 'Trade Substitution Initiatives' would be small-scale in nature, with the minimal bureaucratic intervention and would aim to provide genuine opportunities for the individual farming communities to move away from drug-centred economic activities. 

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