We are actively researching the Life Cycle Assessment for our Super SSR building blocks and the closely associated Hemp Lime material called hempcrete. We found an excellent article from the U.K. university of East London written by Marabel Clark.
“To complete a full Life Cycle Assessment for a building is a very lengthy process. Building professionals wanting to reduce the energy embodied in their designs need to have simpler methods available. The BRE Green Guide to Specification (BRE 2008) offers information on building elements (such as floors and walls) which is incorporated into the widely used BREEAM system, but the information is in terms of ratings, derived from a weighting system. The embodied energy is not made explicit, and the selection includes industry-standard elements only. A designer wanting to use a ‘low impact’ but non-standard material is not able to make comparisons on the basis of the Green Guide. To make up for these deficiencies this thesis has proposed a 3-stage method of material selection, reiterated here in brief as follows:
· Reduce energy inputs: select the low-energy option (energy embodied in extraction + processing/manufacture + transportation).
· Reduce CO2 outputs: select natural materials to sequester carbon
· Select low-carbon products/processes: prefer renewable energy sources
This method recognises the overriding importance of reducing energy consumption, with carbon sequestration and renewable ‘carbon neutral’ energy considered at the second and third stages; because although they can contribute to improvements, they cannot in themselves bring down carbon emissions in the construction industry. The selection process was applied to the case of a planned office building, where operational energy is being kept to a minimum. The ‘sustainable’ choice for the external wall material is hemp lime, and this was compared to a range of highly rated industry standard alternatives (block and brick cavity walls) as described in the Green Guide. Embodied energy data was collected, and wall dimensions chosen to give a comparable U-value. Results from the simplified model used show that hemp lime has an embodied energy lower than at least half of the walls in the sample, but the embodied carbon is relatively high. However the effect of carbon sequestration makes the net carbon emissions of the hemp lime wall negative. An investigation of the energy effect of transportation from factory to site was also carried out. The selection process as applied in the case study showed itself to have clear potential as a way of reducing energy consumption, as well as allowing a preference for plant-based building materials for their carbon sequestration properties.”
This is an excerpt from Marabel Clark MSc Aees Thesis January 2010.
presented to Advanced Environment & Energy Studies January 2010
Graduate School of the Environment, Centre for Alternative Technology , Machynlleth, Powys, SY20 9AZ
Selecting building materials to reduce environmental impact:
Proposal of a method of selection which prioritises embodied energy and carbon;
incorporating a comparative study of hemp lime for external walls.
Please read the complete article here