Hempcrete: The Building Material That’s Good for You and Good for the Planet

Kirstie Wulf of Shelter Building Design holding a hempcrete block

Kirstie Wulf of Shelter Building Design holding a hempcrete block (Belle Butler)

Story by Belle Butler

As we rethink how to live in a warming world, building designers like Kirstie Wulf in Hazelbrook are exploring new fire-resistant building materials like hempcrete. In 2015 Kirstie received the National Building Designers Association Award for her first hempcrete home and she’s been designing them ever since.

Meeting building designer Kirstie Wulf in her Hazelbrook home was a bit like walking into someone’s living room on Christmas morning. Kirstie exuded an energy of barely contained excitement, like she had this secret gift that she couldn’t wait to share. The gift was, in fact, her knowledge about hempcrete, a building material that seems to tick all the boxes you could possibly throw at it.

Key Points:

  • Hempcrete is fire-resistant, offers great thermal insulation and is renewable, recyclable and compostable.
  • Industrial hemp differs from marijuana in that it has a low percentage of the psycho-active property THC and is now legal to build with.
  • Hempcrete can be retrofitted and is easily installed in standard building design.

If you haven’t heard of hempcrete, that might be because stigma and legal barriers around growing industrial hemp in Australia have led to relatively slow uptake of the product. Industrial hemp differs from marijuana in that it has a low percentage of the psycho-active property THC. Nevertheless, growing it for commercial or research purposes wasn’t legalised until 2008 in NSW, and 2017 Australia-wide.

Hempcrete is a mixture of a lime-based binder and hemp hurds, which come from the woody inside of the hemp stalk. Conveniently, this is a by-product of the other uses of the plant. Freshly made, it has a muesli-like texture and is placed in a formwork surrounding a standard timber frame. The following day the formwork is removed and once dry the hempcrete walls can be rendered.

Hemp hurds to make hempcrete

Hemp hurds come from the woody inner stalk of the hemp plant (Belle Butler)

“It’s a lightweight, vapour-permeable and insulating material that is resistant to both fire and pests,” said Kirstie, who is the director and owner of Shelter Building Design as well as a Certified Passive House Designer. “If you are looking for a low embodied energy, healthy and natural building material with great performance, then look at using hemp in your next build.”

Hempcrete v Blowtorch: Kirstie Wulf from Shelter Building Design (supplied)

Kirstie highlights many reasons behind her decision to use hempcrete:

  • Hempcrete is fire resistant. It is rated up to BAL FZ, the highest bushfire rating.
  • It is a carbon neutral product with low embodied energy. From plant to harvest, hemp takes 3-4 months to grow, with low water, minimal fertiliser and little to no pesticide requirements. The plant takes in carbon while growing, then locks it up in the building material. Once set, the lime component of hempcrete continues to absorb carbon dioxide from the atmosphere.
  • It has excellent thermal performance, resulting in diminished or no need for heating and cooling.
  • Hempcrete is vapour permeable. This means that it regulates humidity by absorbing water vapour and releasing it.
  • Hemp is a renewable, natural material resulting in a product of low toxicity. Being natural, it can eventually be composted, or recycled by crushing and mixing 10 % of older material into a new mix.
  • Hempcrete promotes healthy indoor air quality: the lime prevents mould and the vapour permeability results in no condensation.
  • Because of how it is used in construction, it results in well-sealed buildings with no gaps, preventing temperature loss as well as reducing fire risk due to ember encroachment.
  • It acts as excellent acoustic insulation.
  • Because of high silica and lime content, hempcrete is vermin and termite resistant.
  • It boasts design flexibility that allows owners to choose the look they are after.
  • It is achievable for owner-builders to use in DIY projects.
  • It uses a standard timber frame, so it is compatible with standard building practices, easy to run services through, and accessible to conventional builders.
  • It can be retrofitted in existing buildings.

The story of Kirstie’s passion for hempcrete started 21 years ago, well before the product was known or accessible in Australia. She had engaged a builder and was actively involved in the build of her mudbrick house in Hazelbrook. “I knew nothing about building at the time and it was a huge learning curve,” she said. “But I discovered I loved building. I built myself a shed in the backyard, got into natural building materials, did some workshops with the Earth Building Association, and then I finished all of that and thought, ‘oh, I want to keep doing this.’ So I looked up online and saw that you could do a building designers course through TAFE.”

Kirstie holding hemp hurds used to make hempcrete

Kirstie holding hemp hurds used to make hempcrete (Belle Butler)

At the time, Kirstie was working as a lawyer and studying for a specialist accreditation exam which had a 50% fail rate. “I thought, ‘look if I don’t pass this, I’ll do my building designers course and change my career.’ Then when I passed, I was slightly disappointed because I really wanted to do building design. So I went ahead and did it anyway.”

Kirstie’s self-determination, a quality that was evident during our interview, then led her to the discovery of hempcrete. She had bought land on the South Coast at Culburra Beach and wanted to put her newly acquired knowledge to the test by building her own home. “I wanted to use natural building materials but wanted something that was easy, that I could do myself, and had good insulation,” she said. “I stumbled across an article on hempcrete, in Owner Builder magazine. I liked the idea that, unlike some other natural building materials, it is a chemical rather than physical set: once it is set, it will not go anywhere. So it was the good insulation, that it was a natural material, had low embodied energy, had a bit of thermal mass to it, it was light-weight and easy to do that attracted me to the material. I thought, ‘I’ll give that a go.’”

At the time of the build, 2012, Kirstie’s was one of the first hempcrete homes in Australia. She documented her efforts in a blog that gained over 20,000 followers worldwide: culburrahemphouse.blogspot.com, and the completed home received the National Building Designers Association Award in 2015.  “Towards the end of the build, I thought, ‘I love this, I just want to keep doing this.’ So I went back to TAFE, did some more qualifications, got my diploma in building design, and went, ‘that’s it, I’ve got to do a career transition and do this full time.’”

Kirstie’s Culburra Hemp House as displayed in “Hemp Buildings - 50 International Case Studies”

Kirstie’s Culburra Hemp House as displayed in “Hemp Buildings – 50 International Case Studies” by Steve Allen (Belle Butler)

Kirstie later started up her own business, Shelter Building Design, with the tagline: Designing a sustainable future, one house at a time. The company provides a number of sustainable building solutions using natural building materials, but Kirstie’s particular passion for hempcrete sees her advocating for wider use of the product. She has conducted workshops to guide owner-builders on their own projects, overseen a number of builds, started up the Hemp Building Australia Facebook page, which boasts over 10,000 members, and recently co-created the Hemp Building Directory: a one-stop website that links up building designers, architects, engineers, builders, installers, suppliers, and certifiers working with hempcrete and anyone wishing to build with it. “My view is that the more people know about it the more people are going to want to do it.”

Two things that impressed me most about this product: its propensity to withstand fire and the fact that it can be retrofitted in existing buildings. Given the predictions of more frequent and intense fires to come, Kirstie suggests that hempcrete offers security and safety for those building in high-risk areas. We also have existing housing stock that doesn’t have to be knocked down to benefit from using this product.

hempcrete house

  1. LEFT: This Blackheath home met the highest bushfire rating, BAL FZ, by using hempcrete. (supplied)
  2. RIGHT: Interior of a Blackheath hempcrete home. Walls can be finished in soft or sharp style, making hempcrete flexible to suit different design tastes. (supplied)

Leaving Kirstie’s house after the interview, I still felt like it was Christmas morning and I’d just been given an exciting new gift. As I live with my family in an old Blue Mountains home with all the old-Mountains-home-problems you can possibly imagine, I have often felt bereft of solutions that don’t involve knocking down and rebuilding, or moving house. Now it seemed there was another option. I went home, did some further research and announced to my family that, at some point, we would be undressing the old fibro and weatherboard rags of our home and giving it some fresh new clothes in hempcrete.

Take Action:

  1. Learn more about hempcrete via the Hemp Building Australia Facebook page and the Hemp Building Directory
  2. See more examples of hempcrete homes at Shelter Building Design
  3. Consider doing a workshop with the Earth Building Association

Share this article:

This story has been produced as part of a Bioregional Collaboration for Planetary Health and is supported by the Disaster Risk Reduction Fund (DRRF). The DRRF is jointly funded by the Australian and New South Wales governments.

More from around the region

In April 2021 Blue Mountains City Council became the first Council and government entity in Australia to commit to integrating Rights of Nature (RON) principles into its operations and practices. Yesterday we were thrilled to be able to spend a few hours with Susie Talbot, an Australian lawyer, based in the UK, who was visiting on a Churchill Fellowship to explore the implementation of Rights of Nature in different parts of the world. It was inspiring to hear how she has spent decades using the law to achieve transformative change in relation to complex socio-economic and environmental challenges. In 2020, she founded the Anima Mundi Law Initiative to strengthen the intersections between human rights and ecology, and to encourage the practice of law in alignment with planetary realities and collective consciousness. Projects include the creation of a ‘Rights of Nature Toolkit’ and we look forward to working with her into the future. You can read more at her website: https://www.animamundilaw.org/
Photo: Susie Talbot standing in front of Scott Marr`s artwork in the Planetary Health Exhibition space.

#rightsofnature #earthjurisprudence #anewlegalstoryforanecologicalage #ecologicalage #churchillfellowship @churchillfellowship #animamundi #humanrights #ecology #planetaryhealth

Nelson Mandela once said “Education is the most powerful weapon which you can use to change the world”; and William Butler Yeats, the great poet, said “Education is not the filling of a pail but the lighting of a fire.” If you’re a teacher, educator or involved in education in some way in the Blue Mountains the staff of the Blue Mountains Planetary Health Initiative would love to meet you next Monday 20th May when we join the Blue Mountains Sustainable Schools Network to see how we can all join forces to urgently accelerate the change we need to restore the health of our planet. 3.30-5.30 at Faulconbridge Public School. RSVP Beth Healy DirtMum (details in poster)

#sustainableschoolsnetwork #collaboration #planetaryhealth #environmentaleducators #artteachers #englishteachers #musicteachers #allteachers

Our Planetary Health newsletter is now out, sharing inspiring stories from the Lower Mountains to Lithgow: Read it here and subscribe via any of the Local News sites: https://bit.ly/3QKevs6 (link in profile)

Katoomba Area Local News: Living on the Ledge: Saving the Dwarf Mountain Pine

Lithgow Local News: How a Tolkien Fantasy Turned Into Off-grid Reality at Middle-Earth in the Kanimbla Valley

Blackheath Area Local News: Inspirational, Intergenerational Play in Blackheath

Lower Mountains Local News: The Positive Social Impact of the Glenbrook Country Women’s Association

Mid Mountains Local News: Stronger Together: Mid Mountains Neighbourhood Centre Walks the Talk

Springwood Area Local News: People Of Binfluence: The 2024 Binfluencer Awards

#solutionsmedia #hyperlocalnews #planetaryhealth #localstories #inspiration #bluemountains #lithgow

Woohoo we just hit 1 MILLION views on our reel about Physicist Hans Coster and why he`s using nickel-iron batteries.
You can now read the full story and watch a video about him and his wife Tillie at their property Middle Earth (links in profile). We`d love you to subscribe to our Blue Mountains Planetary Health YouTube channel and share the latest video on him there as well.
The video is fabulous:
#offgrid #underground #nickelironbatteries #planetaryhealth #reforestation #selfsufficient #middleearth #bagshotrow

A small group of Blue Mountains women is helping local women survive and thrive and also contributing to improve maternal and newborn survival in developing countries. Assembling birthing kits for women in remote locations is just one of the many ways the @zontaclubbluemountains is empowering and supporting women, both abroad and at home. Read more in Lower Mountains Local News (link in profile)

#womensupportingwomen #maternalhealth #birthingkits #zontainternational #zonta #abetterworldforwomen #localaction #localactionglobalimpact #planetaryhealth

We are thrilled to announce that award-winning health writer and author Sophie Cousins will be leading the workshop: Our Community, Our Stories: Writing for Change from 2-5pm on Saturday 25 May at the Planetary Health Precinct. Sophie`s work has been published in the New York Times, London Review of Books, the Guardian, the Lancet, Meanjin and others. She also works as a public health consultant for the World Health Organisation. The workshop will be followed at 7pm by the launch of the Planetary Health Writers Network. Places are limited so bookings essential (link in profile): https://www.eventbrite.com.au/e/our-community-our-stories-writing-for-change-tickets-895548458547

#writingforchange #impactfulstories #solutionsjournalism #writingworkshop #planetaryhealth #changethestory #thenewsweneed #writersnetwork #bluemountains #katoomba

We`re thrilled to welcome Tamsyn McGrouther to our growing team of volunteer storytellers. She`s reporting on how the Springwood Lot Party transformed an underused space, the car park at Springwood Train Station, into a vibrant community space with food stalls, art opportunities and live music. Read more in Springwood Area Local News (link in profile) : https://springwoodlocalnews.com/springwood-lot-party-2024/
#changethestory #hyperlocalmedia #solutionsmedia #springwood #inspiringstories #planetaryhealth #bluemountains #localnewsmatters

Mushrooms are a hot topic at the moment with more and more research illuminating the essential role these organisms play in the health of the planet as well as the significant health and medicinal benefits they hold for humans. Belle Butler visited local mushroom grower, Alex Felix, at his farm in Lawson to talk about the mighty mushroom. Read more in Mid Mountains Local News (link in profile)

#mushroomgrowkit #mushrooms #fungi #growyourown #lawson #bluemountains

About Belle Butler

Belle Butler is a writer, musician and occasional photographer. She likes mix-and-matching these artforms and often explores the same themes through each of them. Her short fiction has been published in numerous Australian literary journals and she recently received a WestWords Fellowship and Mentorship with Delia Falconer for her novel manuscript, ‘River.’ Hopefully it will be published one day.

You might also like:

Kris Newton of Resilient Villages

Kris Newton & Resilient Villages: Preparing to Reduce the Risk of Disaster

As we face predictions of increasing natural disasters due to climate change, past events show that community-led recovery and preparedness is key to building resilience. Belle Butler talked with Kris Newton of Mountains Community Resource Network about how she prepares to reduce her own risk of disaster, and about MCRN's pilot project Resilient Villages, which aims to equip communities with the skills and tools they need to take control of their own destiny.


Enjoyed this article? Please help spread the word :)