Image Mike Lemanskii
As the global temperature continues to increase, so too does the frequency and intensity of the catastrophic climate events it causes.
Last year was the second warmest on record and brought to an end the hottest decade in human history. In January this year, there were fierce bush fires in Australia, caused by severe droughts and strong winds, that have burned an estimated 18.6m ha (46m acres) of bush, forest and parks across the country. At the time of going to print the BBC reports that at least 29 people have lost their lives due to the fires.
In September last year, the Bahamas was hit by a Category 5 hurricane – the strongest the islands have ever endured. And worse is predicted: in February last year, a study part-funded by the National Oceanic and Atmospheric Administration and published in Nature, suggested that, in future, similar storms will strengthen faster in the Atlantic Ocean.
And the UK hasn't remained untouched by the chaotic weather. Large parts of the country battled floods last year. In November, the rivers Severn and Avon burst their banks, and the Sheffield Met Office weather station reported its wettest ever autumn.
It seems undeniable that climate change is ushering in a new world of extremes, with each posing a unique risk to different elements of the built environment. With that in mind, we take a closer look at precisely what those threats are and, perhaps more importantly, what can be done to mitigate their potentially disastrous effects.
Obviously, tall buildings are particularly vulnerable to extreme wind speeds, especially when it leads to a process called vortex shedding. This occurs when wind moves past a building, creating a fluctuating low-pressure area (vortex) behind it, causing the building to vibrate or sway. The taller and more uniform in shape the structure, the more damaging vortex shedding can be
As cities construct taller and taller buildings in the face of rising urbanisation, innovative solutions to vortex shedding will become more pressing, especially as winds become stronger and more frequent. Research published in November last year, a report in the peer-reviewed journal Nature Climate Change, suggested that shifting global ocean circulation may have triggered a significant change in wind speeds over the past 10 years. Analysing data from 9,000 weather stations, researchers found that in the past decade wind speeds have unexpectedly increased.
Currently, much of the focus on mitigating against this problem is on improving the aerodynamics of buildings, smoothing sharp edges to reduce the strength of the vortices
Shanghai Tower, which stands at 128 storeys and 2,073ft (632m) in height, making it the second tallest building in the world, is a good example of how this works in practice. The tower is susceptible to sways of up to 5ft (1.5m) during the region's regular typhoon conditions and has been designed with a twisting, smooth, triangular shape that has been found to reduce the force of typhoon-strength winds by nearly a quarter.
The tower is also equipped with a 1,200 tonne mass dampener – a computerised stabilisation system that counteracts the motion and slows the sway.
Another method used to minimise the areas where vortices can form is to taper the shape of the building as it rises. This is evident in the design of the world's tallest building, Burj Khalifa in the United Arab Emirates. It rises from a flat base, with setbacks occurring in an upward spiralling pattern and the central core emerging at the top of the structure to form a spire.
However, with space at a premium, tapering isn't always possible – or even desired – as demonstrated by New York City's super-skinny 432 Park Avenue tower, which is a perfect square that reaches 1,398ft (426m) in height.
Rather than tapering the building or smoothing its corners, engineer WSP sought to reduce the likelihood of vortex shedding by omitting the glazing from the mechanical floors, which occur at 12-storey intervals all the way up the tower, allowing air to pass through the building.
But it isn't just tall buildings that are affected: low-lying properties face their own challenges, particularly if they are located in hurricane-prone areas.
Having inspected the devastating impact that Hurricane Dorian had on properties in the Bahamas, quantity surveyor Ron Taylor MRICS says that work still needs to be done in some areas to implement and enforce building codes to better prepare for severe storms. Taylor says inadequately fixed hurricane straps, which play a big part in keeping the roof anchored, as well as the design and installation of hurricane windows and doors, were frequent problems.
While bad design clearly heightened the vulnerability of these properties, elsewhere innovative design is being used to reduce the risks associated with hurricanes.
Not far from the Bahamas, in Miami, Koen Olthuis, from architectural firm Waterstudio, has designed a storm-resilient home in partnership with housing start-up Arkup. Built on water, the home is fixed with several stilts that enable it to move up and down with rising water levels during a storm, and withstand winds of up to 156 mph (251 kph). The first prototype was built last year.
"In an extreme situation, where there is a hurricane – and they've just tested it with Hurricane Dorian – the technology enables the house to move up 6m above the water, so it's really like a growing house says," Olthuis.
Olthuis' firm has also been involved in the building of a sustainable floating neighbourhood, called Schoonschip, in Amsterdam. Schoonschip, which is still under development, will eventually have 46 homes built across 30 floating plots and be home to more than 100 residents.
The idea behind the community is that it makes better use of Amsterdam's available space, while developing houses future-proofed against rising sea levels. So far, 26 homes have been built.
"In the project all the clients try to be as sustainable as possible and try to take as much from the natural energy around them as possible," explains Olthuis. "So, many of the houses have systems in the water that can take heat out of the water during the winter or cold out during the summer."
On this latter point, the heat is generated by water pumps, which extract warmth from the canal water. Tap water is then heated by sun boilers in warm-water pumps, while all the showers are equipped with installations that recycle the heat.
Elsewhere, green infrastructure is being used as a more environmentally friendly way of protecting against storm waves and coastline erosion.
North Carolina had previously tried to tackle coastal erosion by constructing bulkhead walls or stone riprap. But this resulted in loss of vegetation and degraded shellfish habitats along the shoreline, which naturally absorb storm run-off.
To combat this, the North Carolina Coastal Federation, in partnership with multiple public and private bodies, has created living shorelines which are made up of restored salt marsh and oyster reefs – both of which help to reduce the impact of waves and reduce coastal erosion by acting as natural buffers and sponges. In 2019, 2,379ft (725m) of living shoreline was installed in North Carolina.
Michael Floyd, environmental technologist and design director at architectural software company Autodesk, explains how some cities are using similar principles to adapt buildings to deal with increased rainfall and storm run-off, which can cause city drainage and flooding. "A typical response to designing for drainage is to think 'let's channel the water into a sewer drainage system'," says Floyd. "But we also need to think about what we can do at a site-by-site level and think about better utilisation of rain gardens, retention ponds, permeable pavements and green roofs – all ways of catching and allowing water to absorb."
One city that's doing particularly well in that regard is Singapore, largely due to the state's Landscaping for Urban Spaces and High-Rises (LUSH) programme, which places a requirement on developers to integrate green features into their building, the level of which must equal the size of land that was used for the development.
Far from merely improving the aesthetic of the building, foliage also boosts the drainage system, with the plants and substrate absorbing the water before releasing it naturally into the environment at a slower rate.
With these types of benefits in mind, Autodesk came up with a software solution to help designers and engineers incorporate green infrastructure into their building developments. The Green Stormwater Infrastructure (GSI) plug-in works alongside Autodesk's InfraWorks infrastructure design software, which supports the building information modelling (BIM) process.
Floyd explains: "They [Designers and engineers] can choose and customise a variety of techniques – including green roofs, bioretention, harvesting, swales, permeable pavement, trees, infiltration and wetlands.
"GSIs ability to provide real-time feedback on stormwater performance with each design change enables users to iterate quickly compare alternatives, and improve their designs. Engineers, landscape architects and planners can use GSI as part of their early-phase planning and conceptual design process for new or existing development projects."
The recent bush fires in Australia provide a tragic and stark example of how prolonged periods of drought, extreme heat and dry weather can devastate a country. But while it's all but impossible to control wildfires once they spread, innovative design can help protect buildings in the event of a fire.
Ian Weir, research architect at the Queensland University of Technology, is known worldwide for his bush-fire-resilient housing designs including his acclaimed H House which can withstand strong fires. Located in bush-fire-prone Point Henry, Western Australia, the home is elevated on steel stumps and clad in galvanised steel. Bush-fire-rated reflective glazing and fire-rated roller shutters were also installed to the outside of the building to protect against fire embers – which Weir explained to the Guardian in 2016 were the primary cause for house loss in bush fires – as well as timber decks and verandas that are protected by sprinklers.
A more unusual building concept, meanwhile is being tried out by Baldwin O'Bryan Architects elsewhere in Australia. Based on so-called "earth-sheltering" construction, the idea behind the design is that the building is enclosed under stabilised compressed earth blocks – building blocks made from soi l– much like a bunker, which reduces the number of entry points for flames and ember attacks. The blocks have the same bush-fire-resistant qualities as reinforced concrete, which is typically used in earth-sheltered buildings. However, they are a cheaper and more sustainable option, since they can be made from soil taken from the building site.
Elsewhere in the world, heatwaves – like the one that hung over France last July pushing the temperature to 46.1°C (115°F) – are expected to become a more frequent problem. Indeed, in December 2018, the Met Office in the UK said that heatwaves were now 30 times more likely than they would be naturally.
For Asif Dan, head of sustainability at architect Perkins & Will, the buildings most at risk are residential, particularly in northern Europe, where most homes have no air conditioning, which itself doesnt offer a sustainable solution for the long term.
Statistics from energy analyst International Energy Agency (IEA) show that carbon emissions from space cooling tripled between 1990 and 2018 to 1,130 million tonnes. The group says that without significant efficiency improvements, electricity demand for cooling in buildings could increase by as much as 60% globally as soon as 2030.
As such, Dan says the built environment will have to think about more passive design to cool properties. Passive design looks to control building temperature using natural and low-energy solutions and techniques, including thermal mass an example of which can be seen in Council House 2, an award-winning office building, located in Melbourne Australia.
Thermal mass is essentially a heat storage system, in which the heat arising during the day gets stored in exposed concrete ceilings. Then at night, when the external temperature has fallen below that of the internal concrete ceilings windows beneath the low points of the vaulted ceiling, automatically open, allowing cool air to flow through.
Melbourne is also carrying out a "cool roofs" initiative in a bid to control internal building temperatures – as is New York City. This relatively low-cost solution works by layering specialist paint on the roof of a building. The paint includes additives that reflect the sun's heat, and it also absorbs radiation and emits it back into the atmosphere at a higher rate than standard materials could.
At the other end of the temperature scale, cold snaps are an increasing blight across the world. This year, a polar vortex swept in from the Arctic causing temperatures in the American Midwest to drop to -35°C (-31°F) with wind chills as low as -50°C (-58°F).
With that in mind, adequate insulation will be a critical factor for many homes in the UK, which has a lot of vulnerable heritage stock says Floyd. He points to the Rocky Mountain Institute's Innovation Center in the US as an example of the types of solution that could be applied.
The building uses what it calls "aggressive insulation" against the elements and is surrounded by thick concrete walls and levels of insulation three times thicker than that required by regulation.
The centre has also been made 97% more airtight than a conventional commercial building, using advanced materials combined with strict construction details, including two coats of airtight tape and air barriers and seals to avoid leakage.
"This protects against swings in internal temperature, hot or cold, and creates a more stable atmosphere inside the building and comfort for the inhabitants," explains Floyd.
WSP head of London building services Austin Wikner, meanwhile, says it's worth contemplating how tall structures in dense city areas, that are not used to extreme cold, would need to adapt. "If we get to climates where we're regularly experiencing temperatures of -10°C (14°F) or -15°C (10°F), you've got a real potential issue of the build-up of snow and ice, which means there is a risk to pedestrians from falling hazards," he cautions.
"This is a problem they deal with regularly in parts of America, but the UK and London don't tend to have that problem because – at the moment – temperatures don't often get that cold. But as things change, and if we're going to be heading for more extreme temperatures, that's something that could impact design."
As a consequence, he says, the actual shape and form of buildings would need to ensure that snow and ice couldn't build up along any overhangs. Also, consideration would need to be given to the design of the public realm at the base of the building, which may have to include "no-go" zones to protect the public.
"Adequate insulation will be a critical factor for many homes in the UK, which has a lot of vulnerable heritage stock" Michael Floyd, Autodesk