Australia must build to withstand extreme weather

By on 18 April, 2018

Extreme weather events are increasingly prevalent globally.

This article was written by Brett Casson, digital infrastructure leader at Autodesk. It originally appeared in Issue 94 of Position magazine.

Debbie, Marcia, Yasi, George. These are some of the visitors that Australians expect, but are never prepared for.

Insurance companies consistently struggle to forecast the intensity of natural disasters and the total cost of damages. In fact, Suncorp Insurance exceeded its natural hazard claims allowance 10 times over the last 11 years, while IAG exceeded it nine times. Why do we keep spending millions on insurance claims after disasters, rather than invest in more sustainable construction that minimises damage to buildings in the first place? Australians need to rethink how to build cities and towns to better withstand extreme weather.

Australian summers regularly feature severe thunderstorms and flash-flooding, especially in the north. When weather phenomena such as La Niña arrive on our doorstep, Australians become even more at risk of catastrophic weather events that have the potential to devastate communities lacking sustainably-constructed buildings.

Since Cyclone Tracy demolished 70 percent of Darwin homes in 1974, the Australian Building Codes Board made changes to ensure that buildings’ design, construction and performance meet minimum standards to withstand extreme climate related natural disasters. That said, the code doesn’t meet best practice standards and the minimum standards don’t take some hazards into account — such as wind-driven rain, hail, storm surges and heatwaves.

Considering the frequency of extreme weather on our continent, it is clear that Australians must become more proactive about finding more sustainable ways to construct, using all the available technology and tools. Preparation will not only save in costs, but heartache during unpredictable weather circumstances.

The availability of new and improved materials and technology

Today, we have the tools to build to withstand extreme weather. New materials and technologies are available that help fortify buildings against a cyclone’s suite of hazards such as winds, flying debris, and flooding from rain or storm surges. These are often inexpensive and available in a wide range of experimental and off-the-shelf options.

For traditional wood-frame homes in particular, off-the-shelf items can significantly boost resistance to cyclones. New roof attachment methods can add strength, and spray-foam adhesives — which are applied on the inside of the house’s roof and double as insulation — are used for higher wind speeds. To deal with flooding, hydrostatic vents allow water into the home but stop floodwaters from accumulating and potentially degrading its walls and foundation. In wood-frame houses, all of the components are tied together by mechanical connectors. A wood-frame home can be as strong as anything else, as long as all the walls are tied together properly, tied to the roof properly, and the roof and walls are tied to the foundation properly. Specialty metal connectors for this task are relatively inexpensive — around one per cent of the cost to construct an entire house.

Experimental materials can also aid in building sturdiness in the event of extreme weather. Typically, when glass windows burst from high winds, a house will pressurise as wind rushes in, popping off the roof and freeing dangerous debris. Several research efforts are focused on finding glass prototypes that increase the resilience of impact glass. For example, researchers at the Australian National University are studying shatter-proof glass, which relies on engraved ‘microfissures’ to allow it to bend without breaking or fracturing. Currently used in cars, impact glass doesn’t shatter like standard glass.

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Another promising new material on the market is ultra-high-performance concrete (UHPC). UHPC can bend and give, yet is six times stronger than regular concrete. It is made of very fine aggregate, often from recycled materials, such as fly ash and silica fume. The addition of carbon metallic or polyvinyl alcohol fibres allows the material to bend and carry loads even after some cracking has occurred. It is so strong that in 2014, Dr. Chengqing Wu and researchers at the University of Adelaide produced ultra-high performance concrete with high blast resistance against the impact of bombs.

Unfortunately, UHPC is not cost effective for the majority of normal construction projects, given its high development cost as well as the requirement of a license for use. However, the strength of the material means that less is needed for construction compared to standard concrete, making it more efficient by weight and more effective during extreme weather conditions. UHPC’s durability can be seen at one high-profile project in Miami. The Perez Art Museum withstood Hurricane Irma — a Category 5 hurricane which hit the United States in 2017 and became the fifth-costliest tropical cyclone on record — with no damage.

The cost of resilience

With the premiums attached to some sustainable building materials, does it make economic sense for Australians to invest in resilience and construct to last? If we want to achieve best practice standards for construction, rather than minimum requirements, then the answer is a resounding ‘yes’.

An analogy is the cost-effectiveness of a more energy-efficient fridge: there will be a higher initial cost, but lower operating costs. That said, it’s a lot harder to convince Australians about the cost-effectiveness of construction when it comes to future proofing against hazard-related damages. Asking consumers to bank on the worst-case scenario to justify extra expenses is a recipe for under-preparation in almost any context.

In the United States, the MIT Concrete Sustainability Hub has developed a framework that uses data to determine cost-effectiveness in more detail. The Break-Even Mitigation Percentage (BEMP), looks at extreme weather damage likelihood over 50 years in a given location, calculating the amount of damage predicted, as well as the building type and the way it was constructed. It uses this data to determine whether making these structures hurricane-resistant (in the case of the US) is an efficient use of money, and to calculate how soon the anticipated cost savings in an avoidance of hurricane damage will pay back the initial expense.

In the future, the BEMP will expand to include building materials’ carbon footprint and other environmental impacts. It might seem like accounting for a natural disaster is a discrete and singular cost-benefit analysis, but in this way, it’s really an overall measure of sustainability. With this level of analysis, town planners and construction companies will know which areas climate change may make dangerously uninhabitable, and which areas can withstand extreme weather through the aforementioned materials and technologies.

Locally, researchers at the University of Melbourne are looking at how urban planning and natural hazard mitigation can become integrated, as well as the implications of emerging risks on infrastructure, and the differences of construction service capacity across cities and regions.

But, generally speaking, disaster management still has a long way to go in Australia. Challenges faced include a lack of consideration of multiple hazards, no streamlined measurement tools and a disconnect between operations run by the public and private sectors. Neither sector has overtly expressed the realisation that the cost of sustainable construction outweighs the cost of insurance claims that are taken out after extreme weather strikes.

What Australia needs is to implement a framework of its own. Similar to BEMP, it would become a go-to field guide for construction companies to apply weather-resistant materials and methods across a wide range of vulnerable coastlines, matching careful economics with the deep-seated desire to construct to last.

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