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Sustainable uses for hemp October 29, 2007 6:22 PM

This is an exerpt from the Environmental Technologies Action Plan about hemp's use as a superior sustainable building material.

the link is http://http://ec.europa.eu/environment/etap/pdfs/may06_hemp.pdf

Concrete Applications of Hemp in Sustainable

Construction

Hemp confirms to be a high performance and environment-friendly insulating material, when combined with other substances to make linings for walls.

Nowadays, hemp is considered an unconventional material in construction, though it was widely used as a building material in the past.

A research project has shown that hemp-based products provide a high performance alternative to gypsum used in dry lining. The hemp and lime solid composite can be used to make lighter concrete with superior characteristics to those of traditional one; this can be used to produce building blocks, cast like concrete into solid walls or applied wet to the walls of buildings.

Specifically, the research showed that using metakaolin (an altered form of the clay mineral kaolinite) instead of cement, with a small percentage of lime, can produce equivalent or even better results than the usual mixes of lime-hemp or cement-hemp. The results also indicate that the addition of a small percentage of waste paper pulp produces an increase in strength. As lime is a natural biocide, it prevents mould from growing: the new composite material is both environmentally friendly and has the useful quality of reducing the problem of “toxic mould”.

A prefabrication system was also developed.

The material is suitable for the renovation of older buildings, and could be used in developing eco-cottages in Portugal, for example, by avoiding the need to install air-conditioning, thanks to its insulation properties.

This research project to study the characteristics of new composite hemp materials was conducted by a Portuguese University, University of Minho, with the support of a Northern Ireland expert, thanks to the Innovation Relay Centres Network (IRC), an organisation specialised in building technological cooperation in Europe.

The University of Minho is one of the largest universities in Portugal; it is active in research in EU and national RTD projects, and in cooperation programmes with international institutions in the field of Sustainable Construction.

Professor Woolley, from the School of Architecture at Queen’s University Belfast (UK), supported this project: he is a world authority in sustainable building materials, and he had already been involved in many experimental projects on hemp.

May 2006 http://ec.europa.eu/environment/etap 1/2

Industrial hemp hurds

« Hempcrete » block samples

As a crop, hemp shows many advantages: it grows almost anywhere and needs no fertilisers or pesticides, according to Woolley. It can be grown successfully and profitably, as it is more robust and resistant to damp and rot compared to other plants.

A "Hemp Lime Construction Products Association" has recently been set up in the UK and technical guidance and promotion for the use of the material is planned. Other countries are also showing a growing interest. Hemp-based material is lighter, cheaper and provides more insulation compared with gypsum boards: it is ready to become much more popular – a future mainstream material for sustainable construction.

 



This post was modified from its original form on 29 Oct, 18:26  [ send green star]
 
Hemp housing November 06, 2007 12:22 PM

by Rolf B. Priesnitz

Houses built from hemp have been found to use less energy, create less waste and take less fuel to heat than conventionally constructed homes.

Hemp is perhaps best known for its Omega-3 and -6 fatty acids that make it a great addition to a healthy diet, and as a cotton substitute in ecologically-sound clothing and bedding. But it is also a versatile, environmentally-sound building material.

A hemp crop can be grown without the use of herbicides or insecticides and produces up to four tonnes of material per acre per year. Hemp is categorized as a bast fiber crop. It has a stem consisting of an outer skin containing long, strong fibers and a hollow wood-like core or pith. Processing the stems results in two materials: hurds and fibers, both of which have properties that make them extremely useful in building construction.

A variety of wood-like products, such as fiberboard, roofing tiles, wallboard, paneling, insulation and bricks, can be made from the compressed hurds. The fibers can also be used like straw in bale wall construction or with mud in a sort of modified cob style of building.

Foundations can be made out of hemp hurds. A hemp plywood frame is filled with a hemp hurds combined with lime, sand, plaster, some cement and enough water to dampen, and then let to set for a day and to harden for a week. A sixth century hemp-reinforced bridge in France is testimony to the stone-like strength and durability of this material, which has come to be known as “hempcrete”.

Hemp building boosters claim that hempcrete foundation walls are up to seven times stronger than those made of concrete, half as light and three times as elastic. This superior strength and flexibility means that hemp foundations are resistant to stress-induced cracking and breaking, even in earthquake-prone areas. The building material also is self-insulating; resistant to rotting, rodents and insects; and fire proof, waterproof and weather resistant.

Irish builder Henry O’D Thompson of The OldBuilders Company is a fan of using hemp and lime on old stone walls for insulation, condensation, sound muting and breathability. A restoration and conservation specialist who once lived in Canada, he says that lining walls with the hemp/lime mixture makes for a healthy house that doesn’t grow toxic mold.

Pipes can be made out of hempcrete and they, too have greater flexibility and greater elasticity than other those made from conventional materials, and they are resistant to cracking. Stones can also be made out of hemp by wetting the stalk’s cellulose, and forming it into a hard black rock, which can be cut, drilled, cast, carved or formed into any shape.

When hemp hurds are mixed with a combination of lime products, they can produce a light weight insulating plaster, which can be cast around a timber frame or sprayed against a wooden or even stone form. Interior walls can be left exposed or finished with a natural paint. In France, the use of hemp plaster is common, partly because of its high insulation properties but also because it works in old stone buildings.

Steve Allin, a pioneer in the use of hemp as a building material in Ireland and author of the new book Building With Hemp, mixes his own hemp products, which he calls Hemphab, and describes hemp plaster for interior use as having the texture of “sticky muesli”. That, he says, makes it attractive for self-builders who may not have the necessary skills to use the more commonplace plaster. It can also be molded into shapes, textures and finishes.

He cites a social housing project in Suffolk, England as providing a good example of the superiority of hemp as a building material. Suffolk Housing Society built the first two hemp houses in England, as part of an 18-unit social housing development, then studied their performance compared to the regularly constructed buildings. A report was issued in 2002 by the Building Research Establishment (BRE) in regards to the sustainability, economic and environmental differences between the two construction methods. The report’s principal conclusions are that while the hemp homes have far less impact on the environment – they use less energy to build, create less waste and take less fuel to heat – they cost about 10 percent more to build than brick and block houses.

In North America, there are a few hemp houses. In the U.S., the Lakota on the Pine Ridge reservation have constructed a community-based hemp house that was built as a model for sustainable economic redevelopment. The house used hemp and adobe bricks, hemp insulation, and experimented with hemp fiber reinforced cement board.

Another hemp demonstration house, which was much more ambitious in nature, is the rural Ontario, Canada home of Kelly Smith and Greg Herriott, the founders of Hempola, a manufacturer of hemp food and body care products (pictured above). The walls of their spectacular 4,500-square-foot octagonal home north of Toronto are filled with hemp bales in a technique similar to straw bale construction. The floor and ceiling beams of mostly reclaimed wood are stained with hemp oil and the roof is shingled with hemp composite.

With over 120 different projects in the last nine years having used the material in Ireland and over 250 in 16 years in France, this revolutionary but simple material has now come of age. And thus the number of commercially available hemp building products is also increasing. Washington State University has produced hemp fiberboard, which is lighter, twice as strong, and three times as elastic as wood fiberboard, plus it has sound proofing and pressure isolative characteristics absent from wood fiberboard. The process involves chipping the hemp stalk, bonding it together with resins and glues, and clamping it down into molds under high pressure until  [ send green star]
 
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