Hemp Building Materials
Sustainability is something that is very hard to assess especially far into the future so can we apply these evaluations to hemp building materials.Terms such as sustainability and carbon footprints are used to evaluate many building products we use nowadays.
It might be useful to describe what we mean by hemp building materials. There are 2 materials builders obtain from the hemp plant, the hemp fibers which are primarily used to make insulation panels and the hurds or shives, the name given to the woody core particles produced when separating the hemp fibers in the bast or skin from the central woody core.
As the utilization of hemp fibers in the form of insulation panels does not alter the system of construction to a great extent it is a more unusual method of producing a masonry like material from the hurds, that we refer to as ‘Hemp Building’. This material called Hempcrete is in most cases a combination of the hurds and a binder containing Lime (Calcium Hydroxide) and other additives. The casting of this material around a timber frame which provides the structural strength, produces a complete envelope around the building which provides an easily regulated environment for both energy saving and health benefits.
The combination of both insulation and thermal mass creates a problem with building codes as the methods of calculating energy use in buildings both in Europe and the U.S. have been skewed by the fiber insulation industry to suit their materials. ‘R’ values or ‘U’ values as we use in the EU are only relevant to airtight, fiber insulated buildings and do not measure many of the aspects of a buildings performance in reality. We can see from many tests carried out in Universities especially in France and the UK that Hempcrete, hemp building supplies performed well above what would be expected if only using these conductivity measurements of ‘R” or ‘U’ values. So we need a new method of measuring energy use to make Hempcrete more mainstream. This is currently the aim of several PhD students.
Environmental Impact of Hempcrete Housing
As for measuring the sustainability of Hemp or building materials derived from Hemp we can refer to research carried out by the Nova Institute for the Multi Hemp project (1.) which compared hemp with other natural materials used in the automotive and insulation industries. The conclusions of this research showed how the organic fertilizer system of production was the lowest of the materials measured which included Flax, Jute and Kenaf compared to Hemp produced with mineral fertilizer and organic fertilizer. So we know Hemp can be a low input crop and that it also improves soil condition as we have seen improved yields of successive crops such as barley or wheat. There have also been calculations attempted at the CO2 Emissions of Hempcrete taking into account the amount of CO2 stored by hemp during its lifecycle and then subtracting the quantity of CO2 emitted during the manufacture of the lime and other additives in the binder. This was first estimated by Ian Pritchett then CEO of Lime Technology at 110kg per m3. This figure was arrived at by assuming that hemp absorbed nearly 2 tons of CO2 during its life but this is hard to quantify and we don’t know if there is any variation between fibers and hurds and what system is used for harvesting or processing that vary to a degree it could be hard to be definite about. What we can be absolutely sure about is the impact on the environment from living in a Hemp house or working in a Hempcrete structure. Especially in the developed world using other fairly high tech windows or doors it is quite easy to maintain an interior temperature of between 14 & 18 degrees centigrade with no heating or cooling in the U.K so the potential for building homes that need virtually no heating or cooling (What no A.C.!!!!!) thus saving energy throughout the modern world. This is a different approach to the norm as we constantly hear about alternative methods of creating energy rather than not using it and one that would have a far better environmental impact than making other sources of energy we as a species are likely to abuse or waste as we have done in the past.
Quote from Steve Allin Ireland on March 30, 2016 – “At present I am working on projects in more challenging environments such as Haiti and Nepal where just providing shelter from the elements or refuge from earthquakes is of higher importance, the use of energy to either heat or cool their homes is something out of the reach of most. Here the mere production of Hemp is more about resilience or survival than an ‘eco’ economy!”
(1.) Carbon Footprint and Sustainability of Different Natural Fibers for the Bio Composites and Insulation Material. Michael Carus, Martha Barth www.bio-based.eu/ ecology
Article Written by Steve Allin Ireland