There has been growing recognition in recent years of the need to reduce carbon emissions and to safeguard natural resources for the future welfare of the planet. This has led to many people to question current methods of building, as buildings and the builfing industry are responsible for more than 50% of carbon emissions and almost the same proportion of landfill waste. Criticisms of conventional methods of construction, which waste energy and resources, create pollution and poor indoor air quality have led to a search for greener alternatives through which buildings can be created, which are warm, healthy and made from renewable materials. Many ideas have been tried and one of these involves the use of hemp.
There are a number of reasons why the hemp-lime mix is a way forward for ecological building. Apart from being a renewable and non-toxic crop, the mixture of hemp and lime povides a good level of insulation, as well as a form of 'breathing' construction which allows moisture vapour to be absorbed and transmitted through the material. Hemp has particularly interesting properties in terms of absorbing dampness and, when combined with lime, will provide a form of protection to the timber frame which it is enclosing, thus avoiding the need for toxic timber preservatives. Also, the walls of the hemp houses are solid which means that the buidings can also gain from the 'thermal inertia' of hemp lime.
Lime rendering is also an important factor for the health of the occupants of the house.
Hemp as a crop
Hemp is a material that has traditionally been grown throughout Ireland and other countries such as China and France. Farmers were required to grow it to supply fibre for sailcloth and ropes, and many place names reflect the importance of hemp; there is a Hemp Street in East Belfast.
Today hemp is being rediscovered as an ideal crop for farmers who wish to diversify. Permission to grow the industrial, non drug varieties can be obtained and seed is readily available France and Hungary. It grows well in most kinds of soil and does not require pesticides of fertiliser. Hemp has been successfully grown in Counties Down and Roscommon.
Hemp growing has not expanded so far, as considerable investment is required in locally based processing plants which can receive crops from farmers, strip the fibre and chop and clean the hurd or shive which is then used for building. Attemps are being made to pilot a processing plant in Ireland.