The ancient technology replacing air conditioning in Chinese homes

BBC Future

Ru Ling loves spending time in the courtyards of ancient Chinese houses. For them, these places are perfect for hot and humid days.

“They are airy, cool and provide shade,” says Ru, who is 40 years old.

Between 2014 and 2021, Ru lived in a centuriesold wooden house in Guanlu Village (east China’s Anhui Province). She moved there to change her life after living and working in airconditioned buildings for many years.

“The natural cool feeling of my house in the summer was very refreshing and hard to find in the modern world,” she says. “It also gave the home a zen feel and a calming atmosphere.”

Ru says the home’s courtyard contributed to this cooling effect. And she’s not the only one listing the benefits of home patios in warm weather.

Studies have shown that temperatures in the courtyards of some homes in southern China are significantly lower than outside, by up to 4.3°C.

Due to China’s rapid urbanization, fewer and fewer people are currently living in buildings with courtyards. Airconditioned apartments in highrise buildings and apartment buildings are the main forms of housing.

But a renewed interest in traditional Chinese architecture is leading to some historic buildings with courtyards being restored for modern times.

And as the government promotes lowcarbon innovation in the construction sector, architects are already looking to courtyards and other features of traditional Chinese architecture for inspiration for cooling new construction.

Now to heaven

The courtyard or tiān jǐng (天井, in Mandarin literally “well to heaven”) is a typical feature of traditional houses in southern and eastern China. It is different from the open courtyard or yuàn zi (院子) common in the north of the country, which is larger and more exposed to the outside environment.

Courtyards are common in residences of the Ming (13681644) and Qing (16441911) dynasties, designed to accommodate multiple generations of family members, according to a document published in 2010 in the Journal of Nanchang University in China became .

The size and design of courtyards varies from region to region, but they are almost always rectangular and located in the center of the house. They are surrounded on four or three sides by rooms and a wall. Some larger homes have more than one patio.

Courtyards are relatively common in historic homes in much of southern and eastern China, such as Sichuan, Jiangsu, Anhui and Jiangxi provinces. Some of the bestpreserved courtyards are in the historic Huizhou (徽州) region, which stretches between modernday Anhui and Jiangxi provinces.

Long before the invention of air conditioning, courtyards were designed to cool buildings.

When the wind blows across the patio of a house, it can enter the interior through the opening. Because outside air is often cooler than inside air, the breeze rises through the walls to the lower floors, creating air currents by replacing the warmer inside air that rises and exits through the opening.

Yu Youhong is 55 years old. He has been restoring courtyard houses in Wuyuan County, Jiangxi Province, part of the ancient Huizhou region, for 30 years. He has been recognized as an intangible cultural heritage inheritor by China’s Ministry of Culture and Tourism and has extensive knowledge of the courtyards of Chinese houses.

Yu explains that the main functions of courtyards are to let in light, improve ventilation and collect rainwater.

In Huizhou, the courtyards are small and high. He points out that on hot days, the surrounding rooms can block sunlight, leaving the lower part of the terrace cool. And in the meantime, warm air from inside the house can rise and escape through the opening, which “works like a chimney.”

“The ground floor of ancient Huizhou houses usually has high ceilings and faces the courtyard, which is good for ventilation,” Yu said. “Some wealthy families had two or even three courtyards, which provided even better ventilation.”

Cultural and Architectural Revival

Buildings with courtyards have existed in China for hundreds of years. But recently they have been forgotten by many people who prefer modern facilities.

Until the last two decades, with the revival of traditional Chinese architecture as a result of the resurgence of traditional culture in China, courtyards as a whole came back into the spotlight.

One of the houses Yu restored is located in Yan Village, Wuyuan County.

The residence was built 300 years ago and remained abandoned until 2015, when it was purchased by Briton Edward Gawne, a former marketing director for the company, and his Chinese wife Liao Minxin.

With Yu’s help, the couple transformed the threestory house into a 14room boutique hotel.

Gawne and Liao installed air conditioning in all apartments, but kept the common areas around the courtyards in their original condition without fences and with natural air circulation.

Gawne says the terraces are very comfortable in the summer, even without air conditioning. “Everyone notices when they enter the house how naturally cool it is,” he says.

Yu expects courtyards as architectural features to become “increasingly popular” among younger generations because of their ventilation and lighting functions, especially as sustainability becomes an important element in new construction.

Even in the absence of natural wind, air circulation occurs even within a home with a courtyard due to the “chimney effect.” The temperature difference between the top and bottom of the terrace causes the hot air inside the terrace to rise and cooler air to escape from the rooms to the lower part.

Traditional houses further south in the historic Lingnan (岭南) region, which consists of today’s Chinese provinces of Guangxi, Guangdong and Hainan, as well as northern and central Vietnam, have smaller, deeper courtyards due to the longest summer months and hottest in the region.

As a transition space between the indoor and outdoor environments, the courtyard acts as an efficient thermal barrier to protect residents from hot air from outside. However, the greatest cooling effect of the inner courtyard actually occurs when there are bodies of water within the enclosure.

As the water evaporates, it cools the hot air. This process is called evaporative cooling and can be clearly observed in the courtyards of Huizhou.

In the past, families in Huizhou collected rainwater in their gardens because they believed that collecting could protect and increase their wealth. Therefore, the courtyards are surrounded by channels to drain the rainwater that flows down from the roof.

Yu explains that some wealthy families installed drainage systems under their yards to ensure that rainwater only leaves the house after circling the underground entrance hall.

Huizhou’s courtyards also have a large stone tub in the middle to store water for daily use and put out fires.

A 2021 study of houses with courtyards in two traditional villages in Huizhou concluded that evaporative cooling was likely the main factor in causing the average temperature in the courtyards to be 2.6 to 4.3 °C lower than the average temperature at the was on the outside.

Green technology

Currently, government regulations are beginning to play an important role in the return of courtyards to modern buildings. Since 2013, the Chinese central government has been promoting green buildings that conserve resources and emit fewer pollutants throughout their entire service life.

A 2019 government directive required 70% of buildings opened in 2022 to meet its “green” standards, which include a range of specific criteria such as the quality of insulation and the ecological properties of the building material.

Architects are now studying the principles of courtyards to design new buildings that use less energy. One example is the National Heavy Vehicle Engineering Technology Research Center in the city of Jinan in eastern China.

The 18story, glasswalled tower was completed last year. In the center is a huge “skywell” that stretches from the fifth floor to the top. All elevators, bathrooms and meeting rooms are arranged around this axis, which, according to architects from Shanghaibased CCDI Group, helps improve the building’s lighting and ventilation and reduce energy consumption.

In Jixi District of Xuancheng (part of the Huizhou Historical Region), the old town hall building was renovated and converted into a museum in 2013. The complex pays homage to Huizhou’s architectural style, with multiple courtyards that officials say provide air circulation in the interior spaces and help preserve several of the site’s ancient trees.

At the same time, a popular tourist village in Sichuan a province known for its hot and humid summers features a row of round houses with courtyards and large roof overhangs.

Some skyscrapers have adopted the principle of courtyard ventilation to increase airflow without building external courtyards for practical reasons.

An example is the TBA Tower in the city of Dongguan in the Chinese province of Guangdong. With ventilation pipes that function similarly to courtyards, it ensures natural air circulation on all 68 floors.

The aim is to keep the temperature of the building at a comfortable level in spring and autumn and to use only natural ventilation, the tower’s managing director told a local newspaper.

The “green wisdom” of ancient times, which included courtyards, continues to inspire the adaptation of architectural designs to today’s climate and innovations in the passive cooling industry, according to Wang Zhengfeng, a postdoctoral researcher in environmental sciences at the Institute of Area Studies at Leiden University in the Netherlands. Wang previously worked as an architect.

Passive cooling is a method that combines design and technology to cool a building without using energy.

However, Wang points out that there are some difficulties in incorporating courtyards into today’s designs. The courtyard mechanisms that provide natural lighting, ventilation and rain collection are well known, but their principles must be applied in a specific way for each site.

Just as traditional courtyards were built in varying shapes, sizes, and features that depended largely on their natural surroundings—for example, the region’s exposure to sunlight or rainfall—incorporating courtyards into modern buildings requires designers to be sensitive to the situation and the context of their project make it difficult to apply as a universal solution, according to Wang.

“At the same time, artificial lighting, air conditioning and water supplies are now so readily available that we use them without much consideration for their environmental costs,” she explains. “It will not be easy to learn sustainably from the past if we do not think about our current behavior.”

When asked why courtyards have attracted more attention in modern China, Wang says that courtyards are also intended to serve as meeting places for families or communities. They have a ceremonial meaning.

For them, “changes in lifestyle may also have awakened local nostalgia among people living in forests of concrete and glass.”

Read the original version of this report (in English) on the BBC Future website

This report was published here