Effect of temperature on thermal and hygric properties of hemp-lime plasters
Résumé
Hemp-lime plasters are bio-based building materials made with a binder and hemp aggregate. Their main qualities are their low environmental impact due to bio-sourced components and their hygrothermal behavior.
This study investigates two types of Hemp-lime plasters. The first composition corresponds to a mixture of Tradichanvre lime-based binder with hemp shiv (chanvribat). The second composition corresponds to a mixture of Tradichanvre lime-based binder with fibred hemp shiv (Terrachanvre).
This study investigates the effect of temperature on thermal properties (conductivity and thermal diffusivity) and on Moisture Buffer Value (MBV) of hemp-lime plasters. The investigations are based on experimental measurements and are performed at 14°C, 17°C, 20°C and 23°C.
The measurements of thermal properties are made at 50% Relative Humidity (RH). To limit the problems of water migration, the measurements are performed with transient state methods. Hot disk is used at all temperatures; it provides both thermal conductivity and diffusivity. Hot wire is used at 23°C, it provides thermal conductivity only.
The measurement of moisture buffer value (MBV) is performed following the NORDTEST protocol. Specimens are exposed to daily cyclic variation of relative humidity: 8 hours at 75% RH and 16 hours at 33% RH.
Over the considered temperature range (14-23 °C), the impact of temperature on thermal properties is very poorly while it is more sensitive on moisture buffer value. It is shown that the moisture buffer value decreases by about 36% when the temperature decreases from 23°C to 14°C.