Development of Hemp–Clay Composites to Be Used in an Innovative Internal Lining Panel with a Specific Investigation into the Effect of Fine Hemp Shiv on Hygrothermal Performance

Author:
Organisation:
Graduate School of the Environment
Centre for Alternative Technology
Wales
Date: 2014

Rationale

Retrofitting has become an increasingly popular way of improving the energy efficiency of buildings as a pathway to reducing carbon emissions and fuel bills. It also has a central role in meeting a range of strategic policy objectives around, for example, climate change, decent homes, fuel poverty and health. Nevertheless, there are concerns that some materials used in retrofitting may have adverse impacts on the integrity of the buildings and the experiences of their inhabitants, particularly in terms of moisture retention within insulating wall coverings. Consequently, identifying alternative insulation materials or substances that can mitigate such effects will help to maintain retrofitting as a reliable approach, as well as guiding technical specifications in the future.  





Key research Question

The study investigated whether novel biocomposites could address the problem of moisture retention within thermal linings. By undertaking a comparative analysis of six different combinations of hemp and clay, it sought to confirm whether one or more options could provide viable alternatives to existing plasterboard-based solutions in terms of both hygrothermal performance and carbon savings. It built on earlier research into the potential of fine hemp shiv as a natural moisture-buffering component of retrofit constructions.  



Summary of activity

The research involved a number of controlled laboratory-based trials of samples of six novel biocomposites, with a comparison of their hygrothermal performance with that of existing plasterboard insulation materials. The results were used to calculate the potential energy savings if such materials were utilised in panelling retrofits. The trials included measurements of thermal conductivity and volumetric heat capacity as functions of a number of variables.  





Findings

  • All six new biocomposites outperformed both existing gypsum-based plasterboard materials and earlier hemp-based alternatives in terms of thermal conductivity and moisture buffering.  

  • The use of composites of fine hemp shiv and clay appeared to generate lower levels of damp and condensation within buildings, although more testing is required to confirm this. 

  • In a solid wall property, tests suggested that the replacement of plasterboard with biocomposites produced savings of approximately 8% in space heating energy use and roughly 6% in total energy demand. If reproduced on a larger scale, such results could generate significant reductions in carbon emissions. In addition, hemp-based panels appear to be carbon neutral. 

  • Decreases in levels of damp have health implications, and lower household expenditure on energy helps tackle fuel poverty. 



Recommendations

Further research is needed to develop more refined testing regimes that can assess a variety of biocomposite mixes, as well as practical considerations such as the fire resistance qualities of such materials and better mathematical modelling of the cost benefits.  



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