Ancient Chinese Gardens Can Help Mitigate Modern Chinese Urban Heat

We all know gardening is cool, but can gardening be cooling? Huo and colleagues have published a study in the International Journal of Remote Sensing investigating how garden layouts can influence the thermal and wind environment of surrounding urban areas. By examining classical and modern landscaping in both northern and southern cities of China, the researchers have revealed the significant role played by garden planning in moderating heat in cities. This research is important for city planners and environmentalists alike, pointing towards smarter, greener ways to create urban comfort zones while reducing our reliance on energy-intensive cooling methods, like air conditioning.

Huo and colleagues have found that size and water matters – the larger the garden area and the more water features incorporated into it, the more the space cools down its surroundings. This is due to the cooling effects of shade and water evaporation. Conversely, the more buildings in a garden, the hotter they get due to poor wind movement and the heat-retaining properties of structures. The classical Chinese garden at the Summer Palace in Beijing, for example, was found to have a higher cooling effect and reached a wider distance than the modern Taoranting Park in the same city, thanks to its larger size and greater water area.

These insights draw from centuries of Asian traditions of landscaping, where gardens have been viewed as microcosmic recreations of nature and sources of harmony and balance. Space, water, and the green cover have always been crucial elements in these gardens, built to foster a sense of peace and aesthetic pleasure. Today, these classical design elements, the researchers suggest, can offer solutions to the modern issues of heat islands and urban climate modification.

For their research, the scientists used a combination of high-resolution remote sensing and computational fluid dynamics (CFD) to carry out spatial wind and thermal environment simulations of gardens. The four gardens for the study were the modern Taoranting Park and the classical Summer Palace in Beijing, and the modern Jingsi Garden and the classical Humble Administrator’s Garden, in Suzhou near Shanghai. Validation for these simulations came from actual field measurements and meteorological station data, making for robust data sets that allowed for solid, quantitative analysing of garden layout impacts on the local wind and heat environment.

The results were enlightening: The maximum cooling value of the Summer Palace, a classical garden, was 2°C better than Taoranting Park. The distance of the effect was also much better at the Summer Palace, with a cooling distance in the downwind direction as high as 1 km, 800m longer than Taoranting Park. Results were slightly different in Suzhou. Jingsi Garden, the modern layout in Suzhou, had a greater cooling intensity than the Humble Administrator’s Garden. Nevertheless, the Humble Administrator’s Garden had a longer cooling range than Jingsi Garden. Huo and colleagues suggest that the reason is that the Humble Administrator’s Garden has a much more complex shape than Jingsi Garden, and this might both affect the cooling intensity and cooling range. The results show a complicated relationship between garden shape, green plant areas, and water areas in determining their impacts on their thermal environments. The results don’t automatically mean that older is always better, but Huo and colleagues write that there is value in examining classical garden design.

To better play the mitigation role of urban inner gardens, the transforming modern gardens can learn from the construction theory of the ancients. The new concept of combining ancient/modern garden design may optimize the degree of improvement of urban landscape gardens to the local wind and heat environment.

In the final analysis, this study underscores the immense potential of clever, green design on moderating urban climate conditions. It draws a clear line between our horticultural practices and their impact on our environment, demonstrating that how we organize our city spaces can have far-reaching effects on our comfort and well-being and the planet’s climate. As the increasingly palpable effects of climate change take hold, such judicious use of green space could go a long way in reducing our energy use and carbon footprint while also improving the livability of our cities.

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Huo, H., Tao, J., Zhang, W., Guo, L., Leng, P. and Li, Z.-L. (2023) “Urban 3D spatial thermal environment simulation and comparative analysis of Chinese ancient/modern typical garden based on CFD,” International Journal of Remote Sensing, pp. 1–27. Available at: https://doi.org/10.1080/01431161.2023.2227321.