Straw bale moisture testing

Green & Castle Ltd

National Physical Laboratory
Round 3

The Green & Castle vision is to lead in the standardisation of sustainable straw bales as a construction rather than waste agricultural material, providing a route to market which will the currently non-standard construction of natural buildings to be formalised and accepted by the insurers and mortgage lenders and thus opening up the market to larger developers for inclusion as a faster, greener, cleaner and low energy approach to housebuilding and occupation.

Our key objectives are to get a formal and reliable way to measure the moisture in a set of bales such that they can be certified as meeting the standard.

Once this has been completed further measurements can be incorporated to ensure Building Control standards can be met in line with traditional approaches and moving towards purpose built machine for the construction industry.

The main areas of focus include the ability to easily and accurately test multiple bales of straw repetitively and swiftly in order to offer a trusted certificate of standard to purchasers wanted stocks of hundreds of bales for construction projects.

Details of the innovation include the use slicing bales to produce laminar sections, outdoor exposure and artificial wetting processes to measure impact and depth of moisture transfer, provision of water barriers to prevent loss/gain, evolved vapour analysis, microwave measurements at stages throughout the drying process, weighing bales for mass and comparing against other measurement system results, conductance measurements, software visualisation and use of frequency.

Currently single point of use moisture meters can be used to put a long hygrometer probe into any single bale to produce a moisture result.

In practice this rarely happens as the moisture meters are very expensive, take time to have an impact across hundreds of bales and there is no payback for the user.

Testing is therefore done on site after purchase by smell, touch, and feel.

This can lead to either excess waste of bales or higher levels of damp than is desirable.

On completion we hope to have achieved a proof of concept for the reliable moisture testing of bales en-mass that will enable bales to be certified beyond any current level, increasing consumer and developer comfort in the use of straw.

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