OXYGEN FILES UPDATED 15 Feb 20: How about a material that can be harvested in four years, is carbon-sequestering, resilient and perfect for increasingly tropical environments?
There’s a growing interest in the use of bamboo as a structural material in Australia’s tropics. It’s already got form as a traditional material in South East Asia, Oceania and, increasingly, in tropical parts of South America.
Hawaii-based company, Bamboo Living, designs and constructs prefabricated bamboo homes and sells them around the world. Projects have included detached dwellings, multi-residential multi-storey low-rise developments, commercial buildings and hospitality.
Co-founder and architect David Sands was part of the International Network for Bamboo and Rattan committee that developed an International Standards Organization (ISO) standard for structural bamboo.
This enabled his company’s homes to meet the requirements of building codes in the US and other jurisdictions – but it’s not yet referenced in the Australian building codes.
Sands has said that bamboo can address both sustainability issues and also provide a solution for developments in impoverished areas.
It’s cheap, renewable, quick to build with and lightweight. It also resilient to cyclones and earthquakes due to its flexibility, and weight-for-weight has greater load-bearing capacity than steel.
Just four years to grow and harvest
A 2019 paper by Korean researchers Rashmi Manandhar, Jin-Hee Kim and Jun-Tae Kim, also found benefits including a short time-frame between planting and harvesting of around three to four years for the first harvest and annual harvests after that.
- See the research paper, Environmental, social and economic sustainability of bamboo and bamboo-based construction materials in buildings,
It also regrows from the rootstock following cutting, whereas tree roots generally die off and must be removed before replanting.
By comparison, plantation pine takes around 10 years or more to each point of harvest.
Bamboo growers in Australia also told The Fifth Estate that it survives prolonged dry periods, requires no chemical inputs, and involves minimal soil disturbance once planted.
Getting the industry onboard
Structural engineer and PhD candidate at University of Queensland, Mateo Gutierrez, is currently working on research that could see structural round bamboo accepted by Australian building regulations.
He believes it is a material that could transform global construction.
“During testing, we found that when burning, bamboo creates a char layer that protects the inner layers that are not directly exposed to fire, which means it’s relatively hard-wearing in a fire,” he says.
“Like timber, bamboo suffers a reduction in structural integrity at high temperatures, but our goal is to understand how that reduction occurs and how we can predict the failure of load-bearing elements in a building.”
The next step is to develop design frameworks that can predict how bamboo buildings will perform during a fire. These can then be used to inform revisions to building regulations.
There is also a need to address some logistical issues, such as weak production chains. Currently, it appears there are no major structural bamboo product manufacturers in Australia.
But the potential is there – and the sustainability benefits and regional economic benefits could be immense.
“With research advancing in the area of bamboo fire safety, bamboo buildings in Brisbane are closer than we might think,” Gutierrez says.
Bamboo products share some of the features that have given timber a high profile, including similar thermal insulation properties, acoustic properties, and the biophilic feel-good factor of a natural material.
Beyond the regulatory challenges, Gutierrez says there is another hurdle to overcome: lack of interest in the industry outside experimental or bespoke projects.
Not only is the timber industry very strong, it is also very familiar to designers and builders.
There is not a culture of using bamboo here, he says. Investment in bamboo plantations also lags well behind investment in plantation timber.
Elsewhere, it’s having a moment – in the Philippines, for example, a not-for-profit foundation has delivered 1000 homes in seven years using bamboo.
In Thailand, Vietnam and Malaysia, high-end resorts are using bamboo, and in South American nations such as Colombia, it’s also being adopted for low-cost, fast delivery of sustainable dwellings. Even in Canada is looking to bamboo as a material that can help save the planet.
Let’s get inspired by our neighbours
When looking at thermal performance of homes in the tropic zones, concepts from South East Asia tend to give better airflow and ventilation than adapting the architectural styles that have roots in Europe, Gutierrez says.
In Melbourne, you are looking for mass. In tropical zones, you want to “mix with the weather”.
Passive but not Passive House
Australia-based designer and principal of Barefoot Design, Jaye Irving, has designed and delivered bamboo projects around the world and also teaches bamboo design and construction.
He is focused on sustainable design, using natural materials, passive ventilation and passive solar design strategies.
There has been a trend in Australia for builders in the tropics to deliver the “sealed box” with air conditioning.
“The sealed unit mentality means very big energy use,” Irving says.
But looking to design in other parts of the region, there are ways of delivering less energy-hungry buildings without adding to project costs.
Key design elements include a ventilated attic space, and shade for every wall and window all year round.
Airflow is the key aspect, Irving says.
It’s not only the design of the home that matters either. Plantings around a building also help air to move and cool it. As do ponds.
Convective cooling approaches such as high-set louvres work well.
Another thing that works is extensive sheltered outdoor spaces, such as deep verandahs with outdoor cooking and living that can be shuttered in the event of a severe storm.
Inside a dwelling, instead of the “rabbit warren” separate rooms that are standard in project homes, for the tropics it’s better to have open areas and alternative ways of defining and allocating space to assist with air movement.
“It is stagnant air that creates mould,” Irving says.
Irving has completed some bamboo projects in Australia, but it has been challenging navigating the building regulations. He has also used hemp construction for the tropics and says this works well as hemp is anti-fungal – so won’t grow mould.
“I simply wouldn’t do brick housing anymore [in those regions].”
Is the NCC suitable for the tropics anyway?
Some in the construction and design sectors think that the National Construction Code is not sensitive enough for different climate zones.
Executive director of ASBEC, Suzanne Toumbourou told The Fifth Estate this idea needs to be tested with good evidence.
There is research underway at James Cook University in Darwin and also at University of Adelaide in South Australia to look at the question of cooling houses in our tropical regions of Western Australia, Northern Territory and Queensland.
Toumbourou says this is “an important piece of work”.
There are two main kinds of tropical design at play in our north. The first is the lightweight, high-set type, which relies of high levels of natural air inflow and ventilation. The other is the high mass, low-set style – often referred to as the “concrete eskie” – which relies on mechanical fans and/or airconditioning for comfort.
The first type can fail to perform at the energy efficiency levels originally predicted by the design when an owner or occupant retrofits airconditioning.
In a highly permeable, deliberately airy home, it needs considerably more energy for A/C to keep a building comfortable due to constant loss of conditioned air.
In North Queensland onshore winds can ventilate buildings, in Darwin the still air means you need mechanical ventilation
The other complication is each Australian tropical and subtropical zone has its own distinct climate variables in the building code.
In North Queensland, prevailing onshore winds allow for a design response that uses those winds as part of passive ventilation and air movement strategies.
In Darwin, however, air is often still, so mechanical means such as ceiling fans are often installed.
Western Australia varies greatly depending on where a building is located – Broome has better breezes, for example.
The Torres Strait Islands present their own set of challenges, including increased storm vulnerability, constrained energy resources and challenging supply chains.
What works for Cairns may be entirely unsuitable.
The other potential issue with the NCC is the deemed-to-satisfy pathway and its reference designs for homes are based on templates that perform to standard in our lower latitudes.
Where builders in the north are using DTS approaches, again, performance may not be what the code predicts.
For Toumbourou, ideally designers and builders in our tropics would look for better solutions than the concrete eskie, so the housing they build is adaptive to climate change, mitigates emissions, delivers health for occupants and is affordable to operate.
“[Homes] need to be mindful of the place, and the culture,” she says.
“People in certain localities are bonded to the style of architecture in those places.
“The cookie-cutter approach of transplanting southern-style homes doesn’t work well [in the north].”
Beyond what the building codes may specify, Toumbourou says educating industry practitioners in those regions is part of the way forward. There needs to be a deliberate focus on upskilling them about how to adapt their practices to the tropical regions.