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Hemp Architecture

Smokin Moose

Fallen Cannabis Warrior
[This paper was delivered to the 1997 Catalyst Conference at the Univesity of Canberra.
It is an abridged version of a paper presented as part of a Masters of Architecture at the University of South Australia. ]


Hemp is an eco-solution; environmentally friendly and solar powered, it's a renewable source of cellulose, fibre and seed oils. This paper will investigate hemp and it's use in construction, and it's role in an emerging sustainable "Carbohydrate economy". The paper is solution-focussed and will include case studies and life cycle analysis of hemp-based products.

keywords: hemp, sustainability, Hemp-maché, Isochanvré , carbohydrate economy, chemurgy, life cycle analysis, ecological architecture, design,

Hemp and Ecological Architecture

I'm glad this conference is focussed on designing eco-solutions, for we're all too aware of the problems that literally surround us. Ecological architecture is all about eco-solutions, through design. A key component of this is the transition towards ecologically sustaining or restorative development.

This paper will connect ecological design and practice with the re-emergence of a suppressed material - hemp, aka Cannabis sativa , or marijuana, Once a vital military and strategic crop, then demonised and the subject of genocidal attacks worldwide, hemp is now being re-discovered as an environmentally friendly material, with a multitude of applications. This paper will investigate hemp and it's use in construction, and it's place in an emerging sustainable "Carbohydrate economy". A case study and life cycle analysis of commercially available hemp-based products will be used to highlight multiple benefits.

Introduction to Hemp.

Industrial Hemp

Hemp grown for industrial purposes it is specifically excluded under Section 23 of the United Nation Singles Convention on Narcotic (sic) Drugs (Field,1995, pp 69,80 ) Worldwide, over 150,000ha of industrial hemp is currently grown in over twenty countries including Russia, China, India, North Korea, the Ukraine, Canada, Australia, the UK, Spain, Germany, France, Hungary, the Netherlands, Romania, Poland, Yugoslavia (sic), Chile, Pakistan and Slovenia (Field, 1995, p2; Roulac, 1995, pp31-39; Katelaris, pers. comm.). In Australia, hemp for industrial purposes is currently being grown or trialled in Tasmania, South Australia, Victoria, Western Australia and New South Wales, with the support and backing of groups like the SA Farmers Federation (SAFF), SARDI, the York Regional Development Board (YDRB), Australian Institute for Agricultural Sciences (AIAS) and the Victorian Rural Redevelopment Commission ( VRDRC )

The Uses of Hemp in Architecture

Hemp is a unique plant that offers a natural non-toxic, eco-friendly, renewable and low energy materials that can be utilised in literally thousands of ways as Popular Mechanics magazine identified in 1938:

"Over 25,000 products can be manufactured from hemp, from cellophane to dynamite" (in Roulac, 1995, p24):

Building and construction materials are sourced from the plant's tough fibres. These include the bast fibres (or "bark") composed of 53-74% cellulose (Bedetti & Ciarelli, 1976, in van der Werf, 1995, p58) and also the interior "hurd".

Oils from hempseed provide high quality, edible oil with highly nutritious properties (Karus & Leson, 1994, p55; Herer, 1995, pp43-45) but perhaps more significantly, the raw feedstock for bio-plastics, resins, paints, varnishes and shellacs (Karus & Leson, 1995; Roulac 1995, pp26-29). (Remember Rembrandt painted on hemp canvas with hemp paints).

Currently, there are two primary uses of hemp in building and construction that have advanced to the point of commercial availability and economic feasibility. These are the development and utilisation of hemp fibres as composite fibre products like medium density fibreboard (MDF), and other cellulosic composites, and products made from hemp hurds mixed with lime. Hemp mixed with lime has been used as a building material in France since the time of Charlemagne - between 500- 751AD, but is only now being re-discovered (Chènovotte Habitat, 1992, in Herer, 1995, pp,10, 144-151)). Now it's being used to make floors, walls, bricks and insulation panels.

Hemp, "Chemurgy" and the "Carbohydrate Economy".

The "dual-flush" and "hip-pocket nerve" approaches towards sustainability, involving an absolute minimum of behvioural modification and a maximum amount of financial self-interest, are the most likely to work in the here-and-now. From that perspective one of the most promising potential solutions to the problem of combining economic development with ecological sustainability is a transition towards what William Hale, (a biochemist with Dow Corp) coined "chemurgy" and Morris & Ahmed (1995) call the "Carbohydrate Economy". Chemurgy, involves the use of biomass as an industrial feedstock as opposed to petrochemical products. (West, in Roulac, 1994, p11).

Whilst the concept may seem unfamiliar and/or unrealistic; only a century ago the raw materials for most industrial products like textiles, adhesives, inks, paints, varnishes, dyes, medicines and most other chemicals were derived from carbohydrates in the form of plant matter, or to a much lesser extent, from animals that fed on plants (Morris & Ahmed,1995)

Celluloid, the first commercial plastic, introduced in the 1880s, was made from cotton, whilst Bakelite, common in the 1920s, was a plastic derived from wood pulp. Cellophane and rayon, the first plastic film and synthetic fibre respectively, are still made from cellulose derived from trees/ecosytems (Morris & Ahmed, 1995). These are the exceptions, though. Now hydrocarbons have usurped starch, vegetable oil, and cellulose as industrial feedstocks for every industrial product (except paper). Up to 65% of our clothing and virtually all of our inks, paints, dyes, pharmaceuticals, plastics, and hundreds of intermediate chemicals are made from oil (Morris & Ahmed,1995). These in turn are used to make tens of thousands of final products.

It was Henry Ford who first noted that practically everything that can be made of hydrocarbons can also be made of carbohydrates:

"Why use up the forests which were centuries in the making and the mines which required ages to lay down, if we can get the equivalent of forest and mineral products in the annual growth of the fields?"

[ in HEMPTECH, Industrial Hemp Information Network website 1996].

Whilst this question seems innocuous enough, when Ford & Hale joined forces with the American Farm Bureau to develop prototypes of farm-grown and farm-fuelled cars, the rural , decentralised approach it required undoubtedly threatened the petrochemical industry (Roulac, 1994, p11-12).

Benefits of a Carbohydrate Economy

The carbohydrate economy promises economic as well as environmental benefits. Thousands of locally owned bio-refineries that make multiple products from a single biological feedstock could inject billions of dollars into rural economies. The knowledge generated from this new manufacturing sector could become an important export. (Pettijohn, 1994, )

The environmental benefits of a carbohydrate economy are equally significant. Biochemicals generate a tiny fraction of the pollution generated by the manufacture and use of petrochemicals. The use of biological fuels generates far less carbon dioxide than the use of fossil fuels. Finding commercial uses for the 300 million tons of fibrous "waste" products like cereal straw, sunflower and corn stems, flax, wheat, straw, bagasse, kenaf, soybeans, and urban woodchips, generated annually in American rural and urban areas would itself achieve important reductions in pollution. Switching to grasses or crops for making paper and construction materials would save forests (Pettijohn, 1994).

Recent SA trials of hemp achieved greater than 10 tonnes/dry stem/ha. In this case the stem yield is comparable to the wood yield of the best poplar hybrids. As opposed to hardwoods such as poplar, hemp can meet all the requirements of the paper industry for short- and long-fibred pulps for practically any paper or board grade.( Krotov, 1994, p16).

Bast Fibres as Agro-composites

I don't intend to say much about the use of hemp as an agro-composite material as the next speakers will be looking at that in some detail, but I will mention two points: Composites in general, including products made with wheat straw, flax and other agricultural "wastes" now form the fastest growing section of the wood-products industry (Roulac, 1995, p24).

The viability of hemp as a composite material was demonstrated over fifty years ago by Henry Ford. In 1941, after twelve years of research, his Ford Motor Co. unveiled an experimental car made of cellulosic fibres including hemp, flax, wheat straw and sisal plus 30% resin binders, molded under a hydraulic pressure of 1,500 p.s.i. (Popular Mechanics, 1941, pp1-3; Robinson, 1996, p138).

Ford's prototype car was reported to have ten times the impact resistance of steel, and weighed 1,000lbs less than a comparable steel car (Popular Mechanics, 1941, pp1-3). Now European car makers like BMW are again testing hemp products, under increasing pressure to meet European Commission criteria for 70 percent of a car's parts to be made from recyclable material by the year 2000 (Reuters, 1996). John Hobson, general manager at Hemcore, is confident. "We see hemp as partly replacing fibreglass in the door panels and the roof lining" (Reuters, 1996)

Hemp Hurds.

Currently efforts are underway to use the hurds or shives in the production of ecological particle boards and building materials. (Karus & Leson, 1994). Hemp hurds are not only very absorbent, (hence their commercial use today in animal bedding in the UK and EU) but they are also uncommonly rich in silica, a chemical compound naturally occurring as sand or flint. When mixed with lime hemp hurds change state, from a vegetable product to a mineral, in effect "petrifying" or turning to stone, yet weigh between 1/5 and 1/7 that of cement (Michka, 1994, p50). Most popular to date has been the French product Isochanvré made by Chènovotte Habitat, which is used as a building and thermal insulation material in France. To date over 250 houses have been constructed using this material (Robinson, 1995, p13; Ferguson, 1996, p54). Research is ongoing too in the UK and Germany, where hemp hurds have been used for the construction of floors since 1957 (Karus & Leson, 1994, p52).

In France, hemp hurds are now available commercially under several different brand names: "Isochanvré ", "Canabiote" and "Canomose"; and come in two forms; for construction or insulation (Chènovotte Habitat, 1992, p2, in Herer, 1995, p145).

The processing required is similar for both types of product. The bast fibres are mechanically removed in a dry process without chemicals or the need for a retting (rotting) stage leaving behind the interior core, or hurds. These are then "naturally stabilized" (with borax and boric acid?) to make them fire and water resistant (Chènovotte Habitat, 1992, p2, in Herer, 1995, p145). For insulation the product is used in a loose form and is either poured or blown into roofing, partitions, floors or in wall cavities. Isochanvré meets the "norms" of the CSTB (Scientific & Technical Centre for Building) criteria for a good insulating material. In this application it is probably similar to the cellulose-based insulation made from recycled newspapers currently available in Australia.

Unlike these products however, Isochanvré claims one major qualitative difference - a "high thermic capacity" (Chènovotte Habitat, 1992, p5, in Herer, 1995, p148). The term "thermic capacity" is presumably equivalent to thermal mass - an ability to store warmth and later give it back, due it is claimed, to the high proportion of silica within the plant. Chènovotte Habitat acknowledge this is unusual: "Original evaluation is in progress, as the current common insulating materials have no [thermal mass]" (Chènovotte Habitat, 1992, p5, in Herer, 1995, p148).

Empirical evidence from the 250+ houses constructed to date using Isochanvré suggest that this claim is valid:

In autumn, owners of isochanvré houses activate their heating systems 15 days after their neighbours"; less heat is needed in winter and humidity is lower; in summer, isochanvré slabs are 3°F cooler than the ambient air temperature

(Chènovotte Habitat, 1992, p5, in Herer, 1995, p148).

Isochanvré is processed slightly differently for construction purposes. The product is mixed with natural lime (not cement) and water in a cement mixer. Sometimes plaster of Paris (pure gypsum) or 10% river sand is added. At this stage the compound resembles cement. It can be poured like cement, hardens and becomes mold and insect resistant (Michka, 1994, p51). After drying the isochanvré is a lighter, tawny colour with a texture similar to cork. isochanvré claims good thermal and acoustic insulating properties (Chènovotte Habitat, 1992, p4, in Herer, 1995, p147.

It can be utilised in drywall construction between form work, as an interior and exterior insulation or be poured as a floor, or as an addition to the existing slab to raise the level of an existing floor (Chènovotte Habitat, 1992, p2, in Herer, 1995, p145). The forms can be removed within a few hours, whilst the petrification process continues (Michka, 1994, p51). A big advantage of the material is the fact that it makes several layers of conventional building materials superfluous: Isochanvré can replace bricks or cement, a vapour barrier, insulation, and plaster board or Gyprock panelling (Chènovotte Habitat, 1992, pp4-5, in Herer, 1995, pp147-148; Michka, 1994, p51). The only finish required on the exterior is a coat of whitewash, with or without added pigments, whilst the interior can retain the cork-like texture by either waxing or varnishing the finished surface (Michka, 1994, p51)

Chènovotte Habitat makes other claims as to advantageous qualities of Isochanvré which would make it an exceptional material, by any criteria; whether ecological, architectural, practical, or from the end-users perspective.

* Excellent acoustic insulation
* Breathes, prevents condensation
* Self-draining and waterproof
* Non-flammable (no toxic combustion products)
* Resistant to rodents, termites, insects, fungi & bacteria
* (because of silica content)
* Easy to use, flexible and crack-resistant.
* Ideal for cyclone and earthquake prone areas due
* (strength/weight ratio)
* lightness (appreciated in floor renovations)
* Able to use fewer finishing touches; no plaster, painting or wallpaper required.

(Chènovotte Habitat, 1992, p5, in Herer, 1995, p148)

Life-cycle analysis of Isochanvré

Unquestionably, sustainability, ESD or Ecologically Sustaining Development (ESD) will necessitate restructuring of almost all aspects of our society, political economy, culture and lifestyles. An essential part of such restructuring is the adoption and integration of environmental impacts assessment or "life-cycle analysis" of the products we consume. Given the economic and environmental impact of the construction industry, it is critical that the materials utilised minimise pollution and waste, reduce the use of non-renewable materials and maximise the use of renewable sources of energy and materials. The adoption of hemp as part of a shift towards a "carbohydrate economy" fulfills such criteria.

Isochanvré is marketed as an "eco-product" and makes a point of providing life-cycle analysis is a part of this. From its origins as an annual plant that supports agriculture (and hence rural areas), it provides an alternative to forest clearance for woodchipping or timber, obviates the need for mineral exploration and mining and requires no chemical processing in the defibration or stabilisation stages (Chènovotte Habitat, 1992, p5, in Herer, 1995, p148).

From "cradle to grave" Isochanvré has a low environmental impact.. The simple, natural materials mean no pollution of air or water is caused, no waste is produced, with all sections of the plant being used, and only minimal energy is required to process it. It's uniquely packaged paper sacks made of a micro-porous material, designed to be incorporated into the insulation of either attics or floors. The lightweight nature of the product also reduces transport costs. (Chènovotte Habitat, 1992, p4, in Herer, 1995, p147).

Isochanvré 's lime-based nature make it an easy and safe material to work with. Nor does it require any maintenance over time. In fact, the petrification process means that Isochanvré improves with age, an important ecological consideration. It is also biodegradable (Chènovotte Habitat, 1992, p4, in Herer, 1995, p147)..


The task of testing, evaluating, publicising and popularising the extraordinary characteristics of hemp products as eco-solutions in the construction industry has only just begun. It's clear though that hemp offers an innovative and resource efficient alternative for ecological construction. Hemp can and will play a central role in the transition from a hydrocarbon-based economy to a ecologically sustaining carbohydrate-based economy. Hemp Can Save the World!


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J.M. Danenberg B.A. (Hons)
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