RESEARCH EXPLAINER
Hempcrete, moisture and mould
Moisture buffering is useful. It is not a guarantee.
Moisture buffering is useful. It is not a guarantee. Project-specific design and evidence matter.
What the material can do
Hygroscopic materials can absorb and release moisture as surrounding conditions change. Vapour permeability and moisture storage may help a correctly designed assembly manage humidity.
Finishes change performance
University of Bath wall-assembly experiments found that internal linings and paint choices changed moisture-buffering performance. Specify the complete wall and its finish rather than assuming an exposed-material test describes a decorated room.
Resistance is not immunity
Laboratory research on carbonated hemp-lime found that lime inhibited microbial growth compared with untreated shiv, but mould risk remained dependent on humidity, temperature and the tested material. Laboratory observations do not establish a universal safe humidity threshold for every home.
What it cannot promise
A hempcrete wall does not remove the need for ventilation or protection from rain, ground moisture and leaks. No material choice makes a building automatically mould-proof.
What the research tells us
A study of a Danish hempcrete wall found no mould in the inspected wall. Its modelling also highlighted the importance of initial moisture, timber position and the season when construction is completed. One inspected building is not evidence that all assemblies are safe.
Ask your design team
How will the wall dry? Where is timber positioned? How are openings and bases protected? What is the ventilation strategy, and what needs checking before finishes are applied?
FROM CURIOSITY TO A CLEARER BRIEF
What could your home become?
Five simple questions. A useful starting point, not a technical specification.