Pubdate: Fri, 04 Jul 2014 Source: Day, The (New London,CT) Copyright: 2014 The Day Publishing Co. Contact: http://www.theday.com/ Details: http://www.mapinc.org/media/293 Author: Dirk Langeveld Page: 5 "HEMPCRETE" TOUTED AS HEALTHY, ENVIRONMENTALLY FRIENDLY BUILDING MATERIAL It's certainly not the most common building material, but advocates of "hempcrete" are saying it makes plenty of sense for environmentally conscious homeowners. This substance, also known by the registered name of Hemcrete, is a bio-composite material. American Lime Technology, a joint venture of the Chicago-based U.S. Heritage Group Inc. and UK-based Lime Technology Ltd., says the material is made by combining the woody core of the industrial hemp plant, or "shiv," with a lime-based binder. The shiv has a high silica content, allowing it to bind well with the lime. The resulting material is lightweight, only about one-seventh or one-eighth of the weight of concrete. Hempcrete isn't strong enough to use as a structural element; rather, it has to be added to a load-bearing wooden frame or other structural support. American Lime Technology says it is often put together in mortar mixers and added by hand to building cavities. The hempcrete is then given a render coat and finish, making the home exterior look something like stucco. Hempcrete Natural Building Ltd., which is based in Canada, says the material is an effective insulator against noise and provides a breathable shell around a structure. According to the Green Building Press, hempcrete is a good insulator and provides thermal inertia, allowing the building to store heat and slowly give it off to help mainting regular temperatures in the structure. Lime Technology Ltd. was recently recognized with the 2014 Ashden Sustainable Building Award for its work with the material. "This is a huge leap forward on the journey towards zero-carbon buildings," the Ashden judges said in a statement. "By making it cost-effective and commercially viable to use these products, the possibilities for expanding the use of this superior sustainable building material across the commercial and domestic building sectors are boundless." Hempcrete Australia says the use of hempcrete is more environmentally friendly than traditional materials because it avoids the use of non-renewable materials and toxic chemicals. The company says the lime prevents the biological decay of the shiv, and that hempcrete allows for sequestration of carbon through both the growing of industrial hemp as well as the carbonation of lime. The material can also be recycled or will naturally break down if a building is demolished. The company says industrial hemp is a different strain of the plant Cannabis sativa. Though this plant has been used as a psychoactive drug, Hempcrete Australia says industrial hemp cannot be used in this way. American Lime Technology says farmers in the UK, Canada, and Europe grow industrial hempvarieties that have very low concentrations of the psychoactive ingredient tetrahydrocannabinol, or THC. Owen Geiger, writing for the Natural Building Blog, says the fact that industrial hemp is illegal in several areas is one of the drawbacks of hempcrete. Its carbon footprint, though beneficial in building projects, is offset by emissions produced in transporting it from abroad. However, the rules on industrial hemp have been relaxed in some areas of the United States. According to the National Conference of State Legislatures, the 2014 Farm Bill passed by Congress allows state departments of agriculture and institutes of higher learning to grow it. Fifteen states have laws providing for industrial hemp production as described by the Farm Bill, excluding it from drug possession laws and requiring growers to be licensed by the state. - --- MAP posted-by: Matt