Abu Dhabi, UAEMonday 19 August 2019

The heat is on: how cities choose to combat rising temperatures

From shading and vegetation to reflective paint, a mixture of new and old ideas are keeping things cool

With the UK set to reach a sweltering 39C on Thursday, millions of people will be sprinting for the shade or reaching for a cold drink.

Temperatures in Paris are expected to peak at 41C this week while Belgium, Germany and Holland have also experienced a heatwave.

But with the delight of record summer temperatures for some, the issue of how to keep vast city populations cool is an increasing problem for others.

One recent study in the Gulf forecast that the region’s peak daily temperatures would increase by several degrees over the next half-century.

Use of air-conditioning units is one solution, yet experts claim the technology is expensive and environmentally unsustainable.

What is really needed, according to climate and energy specialists, is a renewed focus on alternative methods of cooling, particularly of homes and offices.

Poorly designed, rapidly constructed buildings tend to expend a great deal of energy staying cool, with the ubiquitous glass facades often adding to the issue.

“The International Energy Agency is extremely concerned about the growth in air-conditioning load,” said David Shipworth, a professor of energy and the built environment at University College London.

“We’ve got very sophisticated design packages to design buildings so they use very little energy, but with a few exceptions there’s little cultural appetite.”

Despite concerns, however, some cities, including those in the UAE, are taking steps to address the problem through often very simple techniques.

Factoring in outdoor shaded areas into architectural drawings, using white paint on surfaces to better reflect the sun’s heat, and planting more trees and vegetation are all tried and tested means of lowering temperatures.

Shade

Buildings in the Arab world have used shading since at least the Middle Ages. For example, traditional mashrabiya windows with their wooden latticework provide shade while still allowing airflow. Shaded walkways are another approach.

“The UAE’s traditional towns consisted of clusters of inward-facing courtyard houses connected via narrow pathways, creating shaded areas, reducing heat gains and benefiting from prevailing winds,” said Saeed Al Abbar, chairman of the Emirates Green Building Council.

“The Al Fahidi neighbourhood in Dubai, which was recently restored to keep with the traditional fareej style of neighbourhood design, was based on a network of shaded walkable pathways between homes to channel a breeze through the neighbourhood.”

Shading need not be static: Abu Dhabi’s Al Bahr Towers have 1,049 moving hexagonal shades per tower that are closed under the sun’s gaze, but opened when the sun is not overhead.

Reflection

Pavements, roads and buildings absorb the sun’s rays and can contribute to the “urban heat island” effect, which warms towns and cities.

In Los Angeles, roads have been covered with white sealant, while in New York subsidies have been paid for roofs to be painted white.

The Burj Khalifa skyscraper, centre, stands on the Dubai city skyline. Tasneem Alsultan / Bloomberg
The Burj Khalifa skyscraper, centre, stands on the Dubai city skyline. Tasneem Alsultan / Bloomberg

In the same vein, villas in the Middle East, including Mohammed Bin Rashid City in Dubai, are commonly painted white or in very light colours.

Offering a high-tech twist, several years ago, scientists at the UAE’s Masdar Institute, now part of Khalifa University, developed white paint which reduces roof surface temperatures by 20°C.

Vegetation

The shade offered by trees can ensure urban landscapes absorb less heat by blocking the sun’s rays. The impact is also magnified by “evapotranspiration”, the process of plants and soil releasing water into the air, leading to a cooling effect.

The Marina Bay Sands hotel and SuperTrees grove at the Gardens by the Bay in Singapore. Singapore has a reputation as the Garden City. EPA / WALLACE WOON
The Marina Bay Sands hotel and SuperTrees grove at the Gardens by the Bay in Singapore. Singapore has a reputation as the Garden City. EPA / WALLACE WOON

Dubai’s Madinat Jumeirah makes use of the cooling and shading effects of trees to reduce temperatures.

For more than half a century, Singapore has also been greening itself, helped by building regulations that mandate plant cover in new developments.

The technique has also been employed at Liwa International School in Al Ain, where a “green wall” covers the façade of the building.

Water

Echoing the cooling effects of vegetation, water features such as fountains reduce temperatures, again by evaporative cooling, a characteristic long-used in the Middle East.

“Old Arabian techniques [include] running water over absorbent clay grills,” said Colin Porteous, a senior researcher at the Glasgow School of Art in the United Kingdom. “Evaporative cooling can do quite well with this.”

A woman cools off at the Trocadero Fountains near the Eiffel Tower in Paris. AFP / ALAIN JOCARD
A woman cools off at the Trocadero Fountains near the Eiffel Tower in Paris. AFP / ALAIN JOCARD

Offering a high-rise example, a Malaysian architect, Ken Yeang, is noted for modern designs that feature, as well as vegetation, swimming pools to promote evaporative cooling.

Windows

Taking account of the sun when deciding where to place windows can reduce heating.

“If you’re near the equator, you want to avoid, as far as possible, fenestration [windows] on the east and west sides,” said Prof Porteous.

Most windows are north facing at Madinat Jumeirah in Dubai, which also has a large thermal mass to reduce temperature changes.

In some parts of the world, windows are oriented to catch the sun in the winter (when it is lower in the sky), but not in the summer (when it is higher).

“These ideas around designing buildings to fit the environment have been around for hundreds of years,” said Prof Shipworth.

Airflow

From the Middle East to the United States, buildings and their surroundings have been designed to encourage airflow.

“There are buildings which are wholly passively cooled and naturally ventilated which exploit the ages-old configurations,” said Professor Alan Short, author of The Recovery of Natural Environments in Architecture.

The windtower is a Mena regional example. Dubai’s Al Fahidi neighbourhood, also known as Al Bastakiya, is noted for its windtowers. The structures can either draw air up and out from inside a home or funnel air down into the interior to help keep it cool.

Meanwhile, the “shotgun” house, first built in the United States in the 19th century, promotes airflow by having one room behind the other, allowing windows and doors to be lined up.

Updated: July 25, 2019 05:48 PM

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