Hempcrete is a biocomposite material made from a mixture of hemp hurds and a binder, used in construction and insulation as a sustainable alternative to concrete or plasterboard.

Sustainability is a core tenet informing the design of the university’s new Hobart campus. While investigating locally available materials with a low carbon footprint, Woods Bagot and contractor Hansen Yuncken identified hempcrete as a viable material with unique sustainability credentials and effective acoustic properties.

“Every material was interrogated in terms of its provenance, carbon footprint, and circularity,” says project architect Alastair Flynn.

“After extensive research, we selected hempcrete as one of the key interior materials. Hempcrete is made from Tasmanian hemp hurd; it has a small carbon footprint, is easily recycled, and is biodegradable at the end of its life. It’s also a unique natural material that has not been used in a project of this scale before in Australia.”

This composite has a unique texture and finish that develops natural variations in its surface once poured. With the addition of oxide, the material takes on unique striations, like a ripple effect in its tonal variegation, for an organic aesthetic outcome.

“Oxides can be used to create exaggerated striations in the layering,” says Woods Bagot Associate Phoebe Settle. “But we also rely on the natural colour variation in the hemp hurd that occurs when hurd is harvested from different locations. Soil, weather, and water all contribute to the colour variation of each crop.” 

The acoustic hemp compositions will incorporate a curved geometry and make up the internal walls for meeting rooms within the restored Forestry Building. The prototype installation is an important stage of the process, helping to train local contractors in preparation for laying the scale and unique geometry of the final wall, and to achieve the detailing required to integrate doors and glazing. 

The hemp has been sourced from local supplier X-Hemp, with a production facility in Cressy, northern Tasmania. Flynn adds that much like in the case of mass timber construction, the use of natural hemp materials onsite results in in a pleasing organic aroma, “much like straw”.

Once complete, the total hempcrete volume used within the project will reach more than 207 cubic metres. At practical completion, the Forestry Building will be the largest example of a commercial use of the hempcrete product in Australia.

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