Beautiful, Eco-friendly and Fire Resistant – Why Architects are Choosing Walls Made of Hemp
Image: Casa Feita por Muitas Mãos / Cairn. Image © James Retief
Hemp
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Let’s Talk About Hemp
Sumptuously textured, carbon negative and just a bit more expensive, hempcrete is being increasingly used in eco-friendly building.
Original Article by Maddie Thomas for The Guardian
Why Choose Hempcrete
Michael Leung first came across hempcrete after a family tragedy. When his father-in-law died from asbestos-related mesothelioma, Leung, an architect, swore off using toxic materials in building.
“When you go on a healthy building journey, inevitably you bump into hempcrete,” he says.
Building with hemp is growing in popularity, from public buildings in Tasmania to private homes in Byron Bay, with architects looking to more sustainable materials in one of the world’s most carbon intensive-industries.
With the ability to capture more than twice its own weight in carbon, purported insulation, moisture- and fire-proof qualities, and now with a hempcrete building winning a National Architecture Awards nod, the eco-material is cementing its place in modern construction.
Image: Hempcrete
Time to go Mainstream
Leung first used hempcrete in 2015 when he built an experimental cabin with hempcrete walls and as much recycled material as possible.
Back then, it was a “window into the future” but now, almost a decade on, Leung’s practice, Balanced Earth Architects, has an extensive portfolio of residential and commercial projects, built exclusively with hempcrete.
“Hemp is a really trendy word these days,” Leung says. The material is becoming increasingly popular, but Leung says, “I really want to see it taken much further into the mainstream.”
Hempcrete is Carbon Negative
Hemp takes just 100 days to grow. It has regenerative benefits for soil and is used in a range of industries, from building to textiles.
Once the crop is harvested, the stem – known as hemp hurd – is processed (also known as retting), leaving woody fibres that are shredded and crushed to size. To build, it is most often mixed with lime-based binder and packed into the timber wall frame.
While big architectural gestures commonly feature glass and steel, those building with the material hope to show that hemp can be grand in its own right.
Image: Hemp Retreats
Figtree Hemp House
A stone’s throw from Byron Bay, Figtree Hemp House is one of Leung’s favourite projects.
A striking red oxide wall, created by the clients themselves with guidance from Leung’s team, shows off the exposed, coloured hempcrete. In the sub-tropical climate, the breathable material counters the humidity and any buildup of mould. There is natural cross-ventilation and no air conditioning.
“The great thing about it is, if you did demolish it, you could literally crush it all up, put it in a mixer and reuse it,” Leung says. “There’s really no landfill material.”
Bringing hempcrete on to the national stage is Public Realm Lab’s Powerhouse Place, this year’s winner of the National Award for Sustainable Architecture.
On the banks of the Murray River, the repurposed Mildura power plant site is now home to the first carbon-positive, hemp masonry public buildings in Australia.
Rusted metal sheeting of the boiler house was repurposed, and three new hemp buildings – a cafe, commercial kitchen and public toilet block – slotted into the site. Now a thriving precinct for public use, Powerhouse Place also includes an open mezzanine area and surrounding gardens.
Public Realm Lab hopes recognition for the project will entice others to experiment with hempcrete.
Anna Maskiell, co-founder and principal architect at Public Realm Lab, is already working on her next hempcrete project – a community hub in south Gippsland.
Public Realm Lab have spent years researching hempcrete, which Maskiell describes as a material that “literally breathes”, with great moisture regulation and “incredible acoustic properties”.
“We were really sick of designing buildings that were just less bad, tinkering around the edges with solar panels and that kind of thing,” Maskiell says. “We were really on this mission to try to find a material that was truly regenerative.”
Opportunities Arising for Prefabricated Blocks and Panels
Hemp is most commonly built “in situ”, packed into the wall frame, but opportunities are also arising for it to be used in prefabricated blocks and panels, pre-packed and delivered to site.
It can eliminate the need for timber studs (part of a wall frame), bulky insulation and often synthetic wall linings. Lime render is added, as well as a sealant, to ensure waterproofing. “Hemp is a single system. It’s your insulation, it’s also your facade,” Maskiell says .
“Standard hemp … is about 20% more expensive than double brick construction,” she says. “As the industry develops and diversifies we are seeing a range of prefabricated hemp systems that can reduce the labour costs further.
“It’s a very different way of working, but we think there’s a lot of efficiencies in it.” At the Australian Hemp Masonry Company, the managing director, Klara Marosszeky, promotes the possibilities of the material to architects, builders and owner-builders.
The Possibilities are Endless
At the Australian Hemp Masonry Company, the managing director, Klara Marosszeky, promotes the possibilities of the material to architects, builders and owner-builders.
“It’s really quite light to work with, and it is owner-builder friendly,” Marosszeky says. “The expense in building hemp houses is generally in the labour component of it, much more so than in the material.” As a new material, specialists are typically required to install hempcrete walls.
New projects such as the University of Tasmania’s forestry building and the Lithgow Women’s Shed, a community-led project designed by Envirotecture and using hempcrete for its walls, are proving the material has some traction. For Leung, the movement is already well on its way.
