Abstract
To wean us from our destructive fossil fuel dependency we must produce buildings that are better in both their occupied energy use and their embodied energy content. Bio-composites formed from cellulose aggregates and binders have a low embodied energy and provide an excellent balance of insulation and thermal inertia; when used correctly they can produce efficient and healthy buildings with considerably lower embodied energy than traditional alternatives. These materials are however naturally variable depending on their production method and this has hindered their uptake in a culture of standardised, performance-based codes. In order to gain wider use, it is important that we can model their behaviour representatively. An important, overlooked factor in the behaviour of these materials is the internal structure on a macro scale, in particular the orientation and distribution of the aggregate. As the particles have a defined aspect and orientated structure themselves, the orientation of the particles within the composite may have a considerable influence on the hygrothermal properties. While this is a concept widely acknowledged, the internal structure of bio-composites has not been characterised or adequately incorporated into behavioural models. This work implements a novel method of material characterisation based on digital image analysis to classify the internal structure of specimens of hemp-lime. The results indicate that the internal structure is highly anisotropic with strong directionality in the hemp particles governed by the construction process. A parameter corresponding to degree of directionality has been developed together with a thermal conductivity model based on a weighted average between bounding conditions.
Williams, J., Lawrence, M. and Walker, P. (2015) Thermally modelling bio-composites with respect to an orientated internal structure In; Gorse, C and Dastbaz, M (Eds.) International SEEDS Conference, 17–18 September 2015, Leeds Beckett University UK, Sustainable Ecological Engineering Design for Society.
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Acknowledgments
We would like to acknowledge all the technical staff in the Department of Architecture and Civil engineering who helped on this project and the EPSRC for funding.
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Williams, J., Lawrence, M., Walker, P. (2016). Thermally Modelling Bio-composites with Respect to an Orientated Internal Structure. In: Dastbaz, M., Gorse, C. (eds) Sustainable Ecological Engineering Design. Springer, Cham. https://doi.org/10.1007/978-3-319-32646-7_16
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DOI: https://doi.org/10.1007/978-3-319-32646-7_16
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