BuildingConstruction Products

Thermal Insulation. Thermal insulationproducts(Fig. 20, 21) are the third most important sector of the hemp industryof theEU. These are in very high demand because of the alarmingly high costsofheating fuels, ecological concerns about conservation ofnon-renewableresources, and political-strategic concerns about dependence oncurrent sourcesof oil. This is a market that is growing very fast, and hempinsulation productsare increasing in popularity. In Europe, it has beenpredicted that tens ofthousands of tonnes will be sold by 2005, shared betweenhemp and flax (Karuset al. 2000).

Fig.1. Spun, loosely compacted hempinsulation. (Manufactured by La Chanvrière de l’Aube, France.)

Fig. 2. Loose Isochanvre® thermal insulationbeing placed between joists. (Courtesy of M. Périer, Chènovotte Habitat,France.)

Fiberboard. In North America the use of nonwoodfibers in sheet fiberboard (“pressboard” or “composite board”) products isrelatively undeveloped. Flax, jute, kenaf, hemp, and wheat straw can be used tomake composite board. Wheat straw is the dominant nonwood fiber in suchapplications. Although it might seem that hemp bast fibers are desirable in compositewood products because of their length and strength, in fact the short fibers ofthe hurds have been found to produce a superior product (K. Domier, pers.commun.). Experimental production of hemp fiberboard has produced extremelystrong material (Fig. 22). The economic viability of such remains to be tested.Molded fiberboard products are commercially viable in Europe (Fig. 23), buttheir potential in North America remains to be determined.

Fig.3. Experimental fiberboard made withhemp. (Courtesy Dr. K. Domier, Univ. Alberta, Edmonton.)

Fig.4. Molded fiberboard products. (Courtesyof HempFlax, Oude Pekela, The Netherlands).

Cement (Concrete) and Plaster. Utilizing theancient technique of reinforcing clay with straw to produce reinforced bricksfor constructing domiciles, plant fibers have found a number of comparable usesin modern times. Hemp fibers added to concrete increase tensile strength whilereducing shrinkage and cracking. Whole houses have been made based on hempfiber (Fig. 24, 25). In North America, such usage has only reached the level ofa cottage industry. Fiber-reinforced cement boards and fiber-reinforced plasterare other occasionally produced experimental products. Hemp fibers are producedat much more cost than wood chips and straw from many other crops, so high-endapplications requiring high strength seem most appropriate.

Fig.5. New building in France beingconstructed entirely of hemp. Wall castings are a conglomerate of Isochanvre®lime-hemp, for production of a 200 mm thick monolithic wall without an interiorwall lining. (Courtesy of M. Périer, Chènovotte Habitat, France.)

Fig.6. The “hemp house” under construction onthe Oglala Lakota Nation (Pine Ridge Reservation), South Dakota. Foundationblocks for the house are made with hemp fiber as a binder in cement. Stucco isalso of hemp. Shingles are 60% hemp in a synthetic polymer. Hemp insulation isused throughout. (Courtesy of Oglala Sioux Tribe, Slim Butte Land Use Association,and S. Sauser.)

The above uses are based on hemp as amechanical strengthener of materials. Hemp can also be chemically combined withmaterials. For example, hemp with gypsum and binding agents may produce lightpanels that might compete with drywall. Hemp and lime mixtures make a highquality plaster. Hemp hurds are rich in silica (which occurs naturally in sandand flint), and the hurds mixed with lime undergo mineralization, to produce astone-like material. The technology is most advanced in France (Fig. 26). Themineralized material can be blown or poured into the cavities of walls and inattics as insulation. The foundations, walls, floors, and ceilings of houseshave been made using hemp hurds mixed with natural lime and water. Sometimesplaster of Paris (pure gypsum), cement, or sand is added. The resultingmaterial can be poured like concrete, but has a texture vaguely reminiscent ofcork—much lighter than cement, and with better heat and sound-insulatingproperties. An experimental “ceramic tile” made of hemp has recently beenproduced (Fig. 7).

Fig.7. Renovation of plaster walls of atraditional timber frame 16th century house (Mansion Raoul de la Faye, Paris)with Isochanvre® lime-hemp conglomerate. (Courtesy of M. Périer, ChènovotteHabitat, France.)

Fig.8. Hemp “ceramic tile.” (Courtesy ofKenex Ltd., Pain Court, Ontario.)

INFORMATIONRESOURCES

• (abstract at www.ndp.govt.nz/cannabis/cannabiswho.html).

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