The impact of bio-aggregate addition on the hygrothermal properties of lime plasters

The requirement to improve the environmental impact of buildings has driven changes in their design and the materials used to build them. Notably the amount of thermal insulation has increased together with improvements in envelope airtightness, with the aim of reducing operational energy use. However, an unintentional consequence of these changes has in some cases been a reduction in the indoor environment quality due to insufficient ventilation.

Some bio-based building materials, including aggregates, as well as lime and clay, have the potential to improve indoor environment quality due to their hygrothermal properties. Bio-based insulation materials are currently used as a direct replacement for higher environmental impact materials, however, their use as an aggregate in a plaster allows them to become part of the exposed surface area of walls, contributing to an improved indoor environment quality through passive humidity buffering. The incorporation of bio-aggregates within lime plasters has therefore been investigated to understand their potential for improving hygrothemal properties. In this study hemp shiv and straw have been added in various mass fractions to lime plaster. The effects of aggregate size and mass fraction on performance have been investigated.