New Build and Renovation

Project Leader: Ranyl Rhydwen

Aims

This research aims to appraise and quantify the claims that hemp shiv combined with a cementitious binder (e.g. clay or lime) has the potential to be an energy saving, biodiversity enhancing, carbon sequestering (removing), environmentally enhancing and economically viable insulating building material.

Rationale

The current environmental situation is such that removing carbon dioxide from the atmosphere and improving biodiversity are of primary concern.

Buildings account for around 50% of all carbon dioxide emissions to build, run and maintain because of the high energy and carbon costs of creating building materials and the poor thermal performance of the present building stock. Manufacturing materials accounts for around 20% of carbon emissions, creates waste, hazardous toxins, is reliant on fossil fuels, can be detrimental to biodiversity and the materials themselves often become waste.

Many buildings, as well as being energy inefficient because of poor insulation or draughts, and are also often unhealthy owing to poor moisture control (condensation) leading to mould growth or rot. Therefore there is not only a need to thermally renovate millions of buildings in the UK to improve their energy efficient but also a need to improve their moisture handling ability.

However, reducing draughts leads to a greater chance of internal condensation and increasing insulation increases the possibility of interstitial condensation occurring in the wall (this is why internal vapour barriers are used in dry-lining).  The latter leads to a worsening of the energy efficiency and increases the chances of rot due to wetness in the wall. Using materials that buffer internal moisture fluctuations and that “breathe” (let moisture vapour pass through them) is reported to reduce the likelihood of internal condensation, decrease interstitial wall wetness and save energy, whereas serious concerns are raised about the long term integrity of vapour barriers.

Therefore there is an urgent need for an environmentally considerate insulating material that not only improves a building’s energy efficiency, enhances biodiversity and bio-sequesters carbon dioxide but that also improves the moisture handling ability of the building.

When combined with a binder (e.g. lime or clay), hemp shiv creates an insulating thermally efficient matrix that can be formed into whole walls in new buildings or insulating renders to renovate existing ones.  This “breathable” moisture buffering matrix also improves air tightness and has been shown to be thermally effective. It also has the potential to bio-sequester carbon, be non-toxic, not create waste, and improve biodiversity. As a renovation it is in the scope of many DIYers although labour-intensive and messy.

However there are still several unknowns about this material’s thermal performance and the environmental claims need a deeper clarification as these claims are dependent on the source of the hemp and the binder used. Therefore this research initiative is to investigate the potential of hemp and binder as an environmentally sound, energy improving and moisture handling building material for renovation and new build – and to openly share the findings.