More heatwaves … how to plan for the future

More heatwaves … how to plan for the future

On days when the mercury rises dramatically there is no shortage of advice – or ‘hot’ tips – to keep us cool. But that is only part of a more complex picture. In the long-term, how we design future towns, cities, and communities, and modify our behaviour towards heat, will be even more important.

Climate change, it was said recently, is racing ahead like ‘an athlete on steroids’. This is worrying. With heatwaves now predicted to become permanent features of our weather in the not too distant future, I think we must plan very seriously for heat. We have already started. But there is much more to do … increasingly quickly!

Increasing impacts

For many people, the most damaging effects of warming experienced so far in the UK stem from a powerful surge in Atlantic storms, unprecedented and catastrophic flooding events across northwest Europe that affect us too, and in some instances rising sea levels.

But global warming is a slippery customer. Yes, rising temperatures do create rainstorms. However, they are also the driving force behind heatwaves, urban ‘heat islands’ plus the new phenomena of ‘heat domes’, wildfires, and intense droughts.

This makes environmental planning more challenging because we must now consider extremely wet, extremely dry, and all conditions in between, to be on the safe side.

Some like it hot

Some like it hot

Human physiology has coped with hot climates for circa 300,000 years. By walking on two legs, Homo sapiens sapiens (the wise, sensible, judicious ape) have minimised the body profile they expose to the sun. With hairless skin and the ability to sweat, the human body can also adapt to hotter conditions. But there are limits.

Until recently, our species has been able to thrive in almost all of the world’s environments, given the use of fire and clothing. But the planet’s hottest parts are now too hot for human survival. We have never lived in such conditions before. And we are in retreat!

The result is, firstly, that a growing population will have to live in smaller habitable areas of the globe, and secondly, ‘hot’ hyperthermia, as opposed to ‘cold’ hypothermia, is a very real risk.

Back to the drawing board

In Europe, our historic infrastructure is also working against us. Where affordable, medieval towns used large south-facing windows to gather maximum solar light and heat.

Ironically, poorly insulated homes are heat-traps in summer. Many Europeans still live in poorly constructed housing blocks erected quickly to cope with, firstly, the Industrial Revolution, and post-war migration later.

In contrast, buildings in the Middle East and other hot regions traditionally have small windows looking out into narrow shaded alleyways to minimise exposure to the sun and limit heat retention.

Old towns often stand on riverbanks. As temperatures rise, so does humidity. A further problem is that large expanses of modern concrete and asphalt absorb heat by day but radiate it out at night back into sleeping communities.

Clearly, we cannot demolish and rebuild established cities and towns to suit a warming world. But we can construct new buildings differently and retrofit and adapt existing structures to withstand conditions for which they were not originally designed.

As a result, how we design individual buildings, both the small spaces between clusters of buildings and the large spaces in whole cityscapes, plus the wider relationship between hot urban and cooler rural settings is something we now need to think about constantly.

Be prepared … for everything!

As an environmental consultant, and also a planning consultant, my mantra has always been “preparation, preparation and more preparation”.

I need to quickly mention that Enzygo ( as an independent consultancy fields multidisciplinary teams of specialists who develop innovative solutions to manage many different risk combinations.

In recent years, this has increasingly involved flood risk assessments. However, we now by default automatically include design factors linked to heat management.

As such, we allow for both wet and dry conditions in our environmental audits, environmental impact assessments (EIA), planning practice guidance, environmental management systems, plus environmental permitting regulations, and landscape management advice. The team also carries out ground investigations, traffic surveys, and noise assessments.

However, as the city summaries show later, a key natural cooling tool is vegetation and tree planting, which is why our tree surveys and arboriculture service are often particularly important (arboriculture).

Details of some of our other environmental services relevant to heat management design and planning are available at (hydrology), (permitting), (planning), and (landscape).

What will a hot future be like

What will a hot future be like?

Future summers are set to be hotter, drier, and longer, boxing in spring and autumn, and turning winters into a couple of dreary months punctuated by damaging storms and destructive floods. Blistering heat will be the default for July and August, with elevated temperatures and humidity making sunbathing and working in the open unpleasant and potentially deadly.

At the same time, summer downpours fed by convective storms will be heavy. Little rain will percolate into the ground. Most will flow over the surface to feed destructive flash floods.

Many people could vote with their feet. A general migration northwards and uphill is likely. Cooler conditions may become a big property selling point.

City living

City living

Heatwaves are already by far the deadliest weather-related disasters in Europe, with 140,000 deaths and 83 heatwaves recorded so far this century. In 2020, circa 2,500 people died from heat-related illnesses in the UK.

The Met Office predicts that in the worst case by 2100, the UK could experience 40C days every three to four years. A parallel study pinpoints Europe as a heatwave hotspot with extremes increasing three to four times faster than other mid-latitude regions.

But cities are becoming increasingly popular too. Some 4.75 billion people now live in non-rural areas and almost 70% of the world’s population is expected to be cosmopolitan by 2050.

Making the problem worse

The standard default solution for cooling in cities is more air conditioning. The number of cooling units in the world could grow from 3.6 billion today to 9.5 billion by 2050. If everyone who needs one has one, they could total 14 billion by 2050.

But this brings its own set of problems. Energy-hungry cooling systems use electricity and exhaust hot air outside. Emissions would go through the roof.

Clearly, novel approaches are required, and in particular passive ones that need no external energy.

Making the problem worse

Many cities are moving in this direction, planting trees, and even using high-tech sprinklers to cool the public. The goal is to remove heat, but also prevent any heat build-up that causes problems in the first place.

As a simple example, on sunny summer afternoons, clean white roofs that reflects 80% of the sunlight hitting them back into space are cooler than grey roofs which reflect only 20%.

In fact, the International Energy Agency estimates that with passive methods well-designed cities could save 25% of the energy they now use for heating and cooling.

Small steps and bigger strides

The record-breaking heatwave conditions of summer 2022 have highlighted basic measures we as individuals can take to protect ourselves, plus straightforward design factors that could be incorporated quite quickly into ordinary buildings.

Beyond that, we can learn traditional lessons from the modern mega-city projects of Masdar in Dubai ( and Neom in Saudi Arabia (

However, many other cities around the world are being very innovative in tackling heat and I will look at some of them briefly in a moment.

Staying cool

While keeping ourselves cool and hydrated, we need to take simple steps like closing windows and keeping curtains closed to keep heat out.

Staying cool

Beyond that, for new-build properties and ‘refurbs’ we could see a return of out-of-fashion window shutters, blinds, or tinted glass. Better room layouts to improve internal ventilation flows will also be important.

One option for properties with modern heat pumps is that these can often run on a reverse cycle which pumps cold rather than hot water through radiators. However, this must be built into the system when installed and is not as straightforward as simply flicking a switch.

Going further still, architecture will also need to treat walls and windows facing north, south, east, and west differently – perhaps using the foliage of deciduous trees to shield southern facades in summer which conveniently vanishes in winter. Trees in general will become crucially important.

How other cities do it

What can we learn from leading cities? Many are taking a technical approach. But vegetation is clearly a popular civic solution.

– Dubai – Masdar sustainable city project was launched in 2008 with qualified success. Street temperatures are 15C to 20C cooler than the surrounding desert. A 45-metre-high wind tower pushes a cooling breeze through the streets. Buildings are clustered to create streets and walkways shielded from the sun.

– Saudi Arabia – Neom is an ambitious experiment in building a self-sufficient sustainable desert city in a country dedicated to oil and gas. Success may be based on its use of renewable energy, and specifically how renewables can power desalination plants that turn sea water into drinking water.

Taking the technical route: –

– New York is painting more than 900,000 m2 of its roofs white to reflect solar heat and cut the heat island effect; if white roofs covered all large cities, maximum daytime temperatures might fall by circa 0.50C.

– Nice’s urban architects have installed ‘pavement wetting’ systems to make walkways cooler in summer.

– Vienna’s ‘cool straßen’ (cool streets) provide heat refuges with ‘fog showers’ that spray a fine mist to cool down walkers when temperatures climb.

– Los Angeles is painting roads a lighter shade of grey, with plans to cover more than 250 city blocks and lower surface temperature by 5C to 8C compared to darker colours. Expensive and prone to wear, dogs prefer to walk on it!

But trees are winning out in: –

– Melbourne, Australia, plans a massive urban forest increase to improve air quality, provide shade and reduce mechanical cooling.

– Milan aims to plant three million new trees by 2030 to reduce urban temperatures by 2C.

– Sierra Leone’s capital Freetown wants to plant 1 million trees and increase vegetation cover by 50%.

– Barcelona’s 1.4 million trees modify its microclimate, reduce temperatures, and provide shade; a 20-year tree master plan will increase tree cover to 30% with species resilient to hot temperatures.

Going further still: –

– Frankfurt is creating ‘green living rooms’ around the city where plants provide natural cooling. Another innovation is ‘luftleitbahnen’ – ventilation corridors – stretches of land with no tall buildings or trees that let outside air some 10C cooler flow into the city at rates of up to 40,000m3 per second.

– Stuttgart is in a river valley surrounded by hills that concentrate heat and air pollution. It has built wide, tree-flanked arterial road ventilation corridors to channel cool clean air in from high ground.

– Paris is creating more than 800 ‘cool islands’ in parks, forests, swimming pools and museums linked by cool walkways; a cool island should be more than a seven-minute walk away for every citizen.

– London can get unbearably hot in summer but is using innovations such a 1.5 million m3 of green roof to increase its green spaces and lower temperatures; a ‘cool spaces’ app shows their location.

– Singapore which with highways canopied by lush trees, leafy urban parks, thousands of sideway trees and vegetation-clad buildings aims to become the world’s greenest city.

Please feel free to contact me directly to discuss any of the issues above, or heat in general.

Meanwhile, keep cool.

Matt Travis, Company Director, Enzygo Ltd.

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