Could Hempcrete be the next big sustainable building material?

  •   14 November 2017

Industrial hemp is a variety of the Cannabis Sativa plant, but unlike its marijuana relative, hemp has long been valued for its fiber content, strength and versatility – features that have caught the attention of builders, architects and manufacturers worldwide.

In 2010, North Carolina-based architecture practice Push Design brought to life a ‘breathable’ home prototype whose exterior walls are made of 12-inch-thick Hempcrete. Hempcrete is an eco-friendly compound of industrial hemp, hydraulic lime and water that has an insulating value of R2.5 per inch.


Push House by Push Design

The material sequesters carbon from the atmosphere, and undergoes a natural petrification process as air filters through it. This means it actually becomes stronger over time.


Another example of an alternative housing solution using hemp that has grabbed headlines is Hemp Home: Tiny+ by award-winning New York architect and Passive House consultant, Christina Griffin, who worked with GreenBuilt for the project.

Designed to be the first modular HempHome to reach Passive House standards, and be certified Net Zero by the Living Building Challenge, the project will feature Hempcrete walls that modulate humidity, eliminate the building’s carbon footprint, and have an R-30 insulation.


“Hempcrete materials provide many advantages over other insulation and wall envelope assemblies,” Hemp Home’s project team explains on their Kickstarter page.

“Hempcrete walls are simpler than most conventional wall systems. They don’t need a vapour barrier, additional sheathing, rain screens or complicated engineering to prevent moisture buildup in the walls. Vapour permeable, i.e. breathable hempcrete walls regulate indoor humidity. They allow moisture to pass through the wall instead of getting trapped in the wall cavity.

“Yet they are airtight and provide good thermal insulation. The lime binder provides fire and [mould] resistance, repels pests, and makes the composite extremely durable. Hempcrete provides good racking resistance and becomes structurally stronger over time. It does not deform or crumble and so does not slump or create air gaps in the walls.”

As a prefab modular home, Hemp Homes can be easily customised – whether homeowners are looking to add a bedroom for a child, set up a home office, or seeking to live “off the grid”.

The team is also developing a prefab hemp-lime panel technology that will enable future Hemp Homes to be built efficiently and inexpensively. Currently, Hemp construction is expected to cost about seven to ten percent more than traditional methods. However, as with many other ‘fringe’ sustainable innovations and applications, this higher up-front cost evens out over the lifespan of the building.


Hemp fiber board by Elke Wetzig. Source: Creative Commons 3.0

Despite the many benefits of Hemp in building construction, its use has continued to be limited in Australia for two key reasons. One, the system of curing Hemp is slow and labour intensive. Two, hemp has a stigma attached to it, due to its relation to cannabis. This latter is an unfounded bias, as hemp is completely different from marijuana in function, cultivation and application. In fact, it contains less than 0.3 percent of THC, the chemical responsible for marijuana’s psychological effects.

The Australian Industrial Hemp Alliance was formed in 2015 to combat these misconceptions and support industrial hemp-based business developments in agronomy, oil production, pharmaceutical research and development, clothing and textile, and building-related products.  The group’s work includes producing an Australian Standard for industrial hemp construction techniques, which could be the building blocks needed to change mindsets and drive research into making the curing process more labour efficient.

Then there are the companies who have gained steady ground over the last two decades. The Australian Hemp Masonry first began researching hemp construction technologies 15 years ago. The University of New South Wales is even developing an Australian hemp-lime composite building material.


An artist’s studio designed by Michael Leung and constructed by Balanced Earth combines hardwood timbers with hemp walls and Japanese screens to create a light and airy natural space nestled in the Byron Bay hinterlands.



Source: The Australian Hemp Masonry Company

This year, Western Australia also welcomed its first hemp home, which was constructed in just eight months. Gary Rogers of Ridgeview Building and Hemp, a traditional builder who taught himself about hemp construction, chose the product for its sustainable qualities.


The hempcrete walls of Rogers’ Margaret River residence are sealed with a natural render made of crushed quartz and silica.



Source: Hemp Homes Australia

“It’s natural, it’s clean, and sooner or later I think we just have to move down this path and change the way we build,” Rogers said in an interview with News Corp Australia.

“France has been using this system for the last 40 years, so basically what we are doing is bringing it over here and presenting an alternative [that says]: ‘Look, we don’t need our double-brick home’.

“It’s not rocket science, it’s about working together and nutting it out to make this mainstream. It’s moving away from your owner-hippy kind of people to clients who I’m pricing full architectural homes for. Whether it’s going to be seen to be green I don’t know, but it’s a start. We’re moving in the right direction.”


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