Hemp-Lime Performance in Danish Climatic Context. Thermal Conductivity as a Function of Moisture Content

In order to fit low energy building policies and reduce environmental impact of buildings, construction materials must have good balance between thermal properties and embodied energy. By using such materials, reduction of both operational and embodied energy are achieved simultaneously.

Hemp concrete is a bio-based building material composed of the woody core of industrial hemp and lime based binder. It is a non-load-bearing material, which can be used as floor and around structural frames for walls and roof. The material is characterized by relatively low environmental impact, moderate thermal properties and, high air and moisture permeability. The properties vary with binder composition, mixing and casting techniques, as well as intended application.

This research presents preliminary heat and moisture building simulations of single family house made out of hemp-lime composite. To evaluate the performance of hemp-lime, it is compared to models with common external walls, upon defined parameters.

The article also determines the variation of thermal conductivity for hemp-lime commercial plaster and wall mix, as a function of moisture content. The most promising binder composition and mixing proportions for the wall mixture are identified through literature review; thereafter samples for the experiment are prepared and tested in laboratory environment. Thermal conductivity is found by using Hot Plate Apparatus λ-meter EP500, while moisture dependence is established upon testing samples with different moisture content.

Results from the experiments show non-linear increase in thermal conductivity with increase in moisture content. The results and potential benefits of using hemp-lime are discussed and conclusions are drawn.