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 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 (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” 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.
LEFT: This Blackheath home met the highest bushfire rating, BAL FZ, by using hempcrete. (supplied)
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.
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.
Join the Planetary Health Centre this Sat 6 Dec for the last Skill Share Saturday of the year: Qigong at 9am, Seed Saving & Gardening Group at 10am, and Bushcare at 1.30pm. One perfect day with great company, great coffee and food, and great steps for living a healthy balanced life, while also contributing to the health of our planet for present and future generations. All ages welcome!
Registration links in profile and below.
Register for Qigong here: https://bit.ly/48wlHjD Register for Seed Saving & Gardening here: https://bit.ly/4prcRe7 Register for Bushcare here: https://bit.ly/4oAFDrz
We have a rare opportunity to learn about the newest and best possible ways to support family and community members struggling with mental health issues, at a free talk and afternoon tea provided by Upper Blue Mountains Sunrise Rotary at the Planetary Health Centre at 2pm this Saturday 29 Nov. Hear from Peter Joseph AM, Chair of the Black Dog Institute, and Professor Helen Christensen AO, Fellow of the Australian Academy of Science and former Executive Director and Chief Scientist at the Black Dog Institute. They`ll be in conversation with journalist Emma Rossi. Dr Christensen is a pioneer in using the internet to reach young people struggling with depression. Her digital mental health interventions are used by millions globally, delivering evidence-based therapy for depression, anxiety, and suicide prevention. Her research uses data from smartphones and wearables – like movement, screen use, and sleep – to detect early signs of mental health issues. Bookings essential here (link in profile): https://bit.ly/4oOnYxz
This Saturday Sherlie McMillan from Rotarians 4 Planetary Health will be running a workshop on How to use a sewing machine from 9am at the Planetary Health Centre in Katoomba. Learn how to set up a machine, service it, troubleshoot when it`s not sewing correctly, and learn some basic sewing skills.
Bookings essential here (link in profile): https://events.humanitix.com/how-to-use-your-sewing-machine
NB. This class is a prerequisite for our very popular Fashion Upcycling classes held once a month.
We`re thrilled to announce that Professor Helen Christensen, a pioneer in using the internet to reach young people struggling with depression, will be joining the conversation with Peter Joseph AM from the Black Dog Institute and journalist Emma Rossi at the Planetary Health Centre at 2pm this Saturday 29 November. Helen was the Executive Director and Chief Scientist for the Black Dog Institute for 10 years and has now been elected a Fellow of the Australian Academy of Science. Her digital mental health interventions are used by millions globally, delivering evidence-based therapy for depression, anxiety, and suicide prevention. Her research uses data from smartphones and wearables – like movement, screen use, and sleep – to detect early signs of mental health issues. This free event is being co-hosted by Upper Blue Mountains Sunrise Rotary and the Blue Mountains Planetary Health Initiative. Afternoon tea will be provided. Bookings essential here (link in profile): https://bit.ly/4oOnYxz
Human composting is increasingly being legalised around the world. Read about it in Katoomba Area Local News here (link in profile): https://www.katoombalocalnews.com/legalising-human-composting/
If you’d like to see this option available in NSW you can now sign a live petition to the NSW Parliament here (link in profile): https://bit.ly/43QIHbz
Thanks to everyone who contributed to deliver a fantastic Disaster Risk Awareness Expo and Family Day yesterday. @mark_greenhill_mayor opened the event at which we celebrated the 13th birthday of Betty the Asbestos Education House; @firecoat_au demonstrated and launched its range of fire retardant products that can help protect homes, gardens and even electricity poles; the Bushfire Retrofit Toolkit was launched; Santa arrived and delighted young and old; and @plantinspired99 and Action for Animals fed us all with a delicious plant-based sausage sizzle. The day was filled with talks, workshops, stalls and the sharing of a huge amount of expertise to keep us, and the other species we share our planet with, safe and healthy! @southkatoomba.rfb @nswses @fireandrescuensw @nswrfs @redcrossleura @redcrossau @shelter.building.design @firehalo.au @asbestosawareness @amelie_ecology @bbagsbluemtns @wireswildliferescue @handsheartfeet
Our marquee is up and we`re excited about our Expo and Family Day tomorrow (Sat 22 Nov). There`s something for everyone from a free sausage sizzle, plants from Santa and drumming and pollinator workshops, to sessions on keeping you and our community safe from extreme weather events and hazardous substances like mould and asbestos. Learn how intumescent paints can slow the spread of fire and pick up a sample pot; check out all our emergency service organisations; learn how to dispose of hazardous materials; paint a native orchid, make some seed balls or sew a boomerang bag to give as plastic-free Christmas presents this year; enjoy coffee and locally made sweets; and get tips on how to retrofit your home safely and beautifully to be prepared for future extreme weather events. View the full program and register here (link in profile): https://bit.ly/4nFrY1J
There are so many new and innovative ways of doing things, like the new cooking techniques being explored by Michael from Good Fat Pastry, and the new fire protection methods being launched at the Planetary Health Centre`s Expo and Family Day on Sat 22 Nov. Check out Michael’s recent presentation at the Food Security Fair in our video here: https://bit.ly/4pnXbIg (link in profile) and come along to taste his delicious carrot cake and pastries at the Expo on Saturday. Check out the program and register to attend here (link in profile): https://bit.ly/4nFrY1J
In 2006 Peter Joseph’s son Michael suicided after a 14-year episodic battle with mental illness. Peter is now the Chair of the Black Dog Institute which is working to achieve better outcomes for all those struggling with mental health issues. Journalist Emma Rossi will engage Peter in an intimate and moving conversation about a life of purpose and mental health advocacy. As a Rotary scholar Peter will also reflect on how Rotary helped shape his values and sense of purpose as a young man - and how those early lessons continue to guide his work today. This free event is being hosted by the Upper Blue Mountains Sunrise Rotary Club and the Blue Mountains Planetary Health Initiative on Saturday 29 November from 2-4pm at the Planetary Health Centre at 33-39 Acacia St Katoomba. Afternoon tea will be provided. Bookings essential here (link in profile): https://bit.ly/4oOnYxz
Learn about intumescent fire retardant paint and a range of other strategies to prepare for extreme weather events, and to manage hazardous materials, at the upcoming Expo and Family Day at the Planetary Health Centre on Sat 22 Nov. You can register to attend here (link in profile): https://bit.ly/4nFrY1J We checked out how intumescent paint works in this video.
When temperatures reach a certain point the intumescent paint begins to swell and expand, often up to 50 times its original thickness. It forms a thick, carbonaceous "char" that acts as an insulating barrier. This layer slows the rate at which heat reaches the structural elements and buys valuable time for people to safely exit a building during a fire. It makes the structure safer for firefighters and rescue teams. #intumescentpaint #fireretardant #bushfire @firecoat_au...
Mould, lead paint, asbestos, silica dust from engineered stone bench tops and a wide range of chemicals, are amongst some of the many hazardous substances entering our environment and negatively impacting our health. Asbestos is found in over 3000 products including textured paints, moulded garden pots, brake pads and clutch linings in older cars, floor and ceiling tiles, lino, fibro, roofing, pipes and gutters, hot water systems, backing for switchboards and insulation boards in air-conditioning ducts, insulation, sealants, fillers, caulking and adhesives, gaskets for industrial and lab equipment and more. We’ll have information to take away and Blue Mountains City Council and the Asbestos and Hazardous Materials Consultants Association (AHCA) will be running free workshops on how to identify and manage these hazardous substances at the Planetary Health Centre`s Disaster Risk Awareness Expo in Katoomba on Sat 22 Nov. Find out more and register to attend here (link in profile): https://bit.ly/4nFrY1J
Are you ready for the next bushfire, heatwave or flood? Why not take steps to prepare at the Planetary Health Centre`s Expo and Family Day on Sat 22 Nov. Award-winning Hempcrete designer Kirstie Wulf from @shelter.building.design will share 10 steps to build or renovate for sustainability and resilience; engineer Mark Liebman will share how you can build a green roof to reduce stormwater runoff and cool your building; Dr Agnieszka Wujeska-Klause will share research results on the most appropriate actions to lower heat in summer and help you use a thermal imaging camera to identify which surfaces retain the most heat; Frank Inzitari will introduce you to the @firehalo.au which can help reduce ember attack; and a team from the University of Technology Sydney (UTS) will work with you to use the Bushfire Retrofit Toolkit to design your own personal bushfire plan. We`ll also be launching Firecoat`s new Bushfire Home Protection Kit. Learn more and register to attend here: https://bit.ly/4nFrY1J
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.
The Homes for Older Women (HOW) program is a successful community-based solution to the national housing crisis. Since launching in May last year, the Blue Mountains not-for-profit has secured accommodation for 47 older women facing housing insecurity and homelessness.
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