University of Bath

Resolving uncertainty in the thermal performance of natural fibre insulation materials

Our research supported a growing 'green economy' by providing dynamic thermal performance data for Natural Fibre Insulation materials.

An Experimentation on hemp lime construction
Investigating the breathability of natural fibre insulation

Nearly half of energy generation in the developed world is inefficiently used to heat, cool, ventilate and control humidity in buildings. Inorganic insulation materials dominate the building industry. But interest in the use of natural fibre insulation products is increasing.

Natural fibre insulation (NFI) is an excellent form of carbon emission mitigation. It reduces the in-service carbon emissions of buildings through reduced energy demands. And, by using plant-based fibres, carbon is stored within the material as a result of plant photosynthesis. This significantly reduces the global warming impact of the insulation material.

Yet, much is unknown about the performance of NFI materials. Where evidence-based data are available they are mostly based on steady-state test performance data rather than the more complex dynamic variations experienced in real buildings. Where there is test data relating to thermal conductivity, it is based on standard test conditions of a material in a dry state and at one mean temperature.

Practitioners use these test results to predict in-service energy performance or evaluate retrofit benefits. This is often without considering the variability due to the changeability in the material's thermo-physical properties, or the validity of the test conditions.

While this situation affects all building materials, there have been attempts to test sensitivity and the impact on energy performance for more conventional products. But, there is little evidence of the same approach for NFI. Furthermore, the hygroscopic nature of NFI materials results in much greater variability in their thermal performance.

Acknowledgement

The project was funded by EPSRC as part of the Building Ops & Management Programme (EP/J019917/1).