Lime-hemp as Wall Insulation - Hygrothermal Performance Analysis by Validated Simulations

Abstract

The application of lime-hemp as a thermal insulation material is promising: besides its ecological benefits, lime-hemp has a reasonably low thermal conductivity, combined with a good moisture buffering capacity and high thermal inertia. However, adequate design and accurate execution on-site are required, as severe long-lasting moisture accumulation could cause the hemp shives to degrade. In this study, a numerical simulation model is validated using long-term measurements. Then, it is further used to evaluate the hygrothermal performance of lime-hemp as both external and internal wall insulation. The simulations show that high humidity levels are found in lime-hemp as external insulation if an external render with inadequate rain protection is used. If the lime-hemp is used as internal insulation, its high vapour permeability allows the masonry to dry towards the inside, resulting in a drier wall compared to vapour tight materials such as cellular glass.