Considering the rather small size of the environmental building movement, it is interesting to discover that there are various camps and groupings within it, with some notable debate taking place between them. The most striking difference of all has often been between the ‘energy’ and ‘ecology’ wings, or to give an example, between the ‘energy nuts’, as a well know eco materials professor once referred to ‘them’, and the ‘hairy shirts brigade’ as another professor of equal standing likewise countered. The gap between such colleagues is often wide, is generally counter productive and needs to be bridged.
One such area of bridge building is the world of bio composites and in particular the development of lime hemp as a bio composites material, which has serious ecological and energy credentials, and is attracting interest from both wings of the environmental movement, not only those concerned about toxicity, embodied energy and so on. but and also those interested in U values and thermal performance. Indeed lime hemp’s carbon sequestration capability should be music to the ears of any ‘energy enthusiast’ as carbon reduction is often a prime driver of the energy lobby.
However it is not just the excellent environmental credentials of this material that are of interest, but also its versatility and potential to integrate into current building systems and solutions. It is this potential to mainstream that is most significant and could multiply the positive environmental benefits exponentially.
Lime
Lime has been used as a construction material for thousands of years. Some of the first cement uses were actually lime-cements with examples of lime concretes being used in Rome for both civil and building projects including, for example, various ‘limecrete’ specifications used within the walls and roof of the Pantheon.
There was a decline in lime cements following the fall of the Roman Empire, with the next main resurgence of lime cements occurring during the 18th Century. Major building and civil projects were undertaken across Europe during this period with extensive research being undertaken into the properties, mixes, specification and techniques of lime cements, such that by early 19th century lime was in extensive use.
Hemp, one of the strongest natural fibres, is a renewable material, with a fast growing season and potential for 3 harvests per annum
However the development of portland cement in 1824 by Joseph Aspdin was to lead to a decline in lime use and specification, particularly for structural use, and eventually even for renders and mortars, which in the UK and Ireland have also become dominated by portland cements.
Despite the decline of lime production, specification and use in the industry, there are aspects and properties of lime that are very positive in environmental terms, which may be critical to its resurgence, in particular its capacity to enable bio material composites.
Lime has many environmental positives, being a natural material, which in processing has lower embodied energy and carbon values than portland cement. It is vapour permeable and hygroscopic, the principle properties of breathability. It has ‘self healing’ properties and does not require movement joints. Lime can be used as a render, plaster, mortar and even as a cement agent under certain load and setting conditions, and lime mortar can allow recycling of brick and blocks at end of use. Lime has the potential to be harvested and processed on a local level and there are many examples of historical local lime sources enabling production in Ireland. Crucially, lime can act as an enabler of bio materials such as hemp.
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