Dennis Lee

Opinion | How green design can aid Hong Kong’s climate change fight by taking heat off buildings

Landscaping and other green design features are not just pleasing to the eye but can reduce buildings’ overall heat gain, lowering the need for air conditioning

While not a panacea, green design features can limit damage to the environment, bring safety and comfort to users and cut energy consumption

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A combined green roof and solar photovoltaic system at One Taikoo Place in Quarry Bay on July 15, 2021. Green roofs and other green building techniques can help cool buildings and reduce use of air conditioning units, which in turn improves the environment and helps the fight against climate change. Photo: Edmond So

Dennis Lee

Published: 1:30pm, 21 Oct 2022

Weather records are dropping one after another. We had the hottest Chung Yeung Festival since records began in 1884 with the mercury climbing to 33.5 degrees Celsius. We had the hottest September day at 35.9 degrees. In July, we had 25 “hot nights” – defined as a minimum temperature of 28 degrees or above – the highest number in a month ever.

This extreme heat phenomenon was not limited to Hong Kong but affected the world at large. China logged its hottest summer since 1961, with cities in Sichuan province experiencing a series of August days over 40 degrees. India and Pakistan suffered from spring heatwaves that hit as early as late April, with the temperature reaching 50 degrees. Europe, North Africa and North America were not spared, with often-extreme heat combined with droughts and wildfires overstressing power grids while people were advised to limit electricity usage.

Extreme heat does not simply make us uncomfortable. Studies show it can trigger serious health issues including heatstroke, heart attacks and dehydration. Researchers at the University of Southern California found that when extreme heat mixes with pollution – which is common in urban areas – the toxic particles from vehicle emissions could worsen ground-level ozone and induce respiratory distress. Extreme heat also hurts economic growth by decreasing work productivity, affecting crop yields and setting off power shortages when supply cannot meet demand.

Since architects and engineers discovered two interdependent materials as being reliable and long-lasting more than 100 years ago, most buildings and infrastructure have been built with concrete and steel. Concrete is great for compression and steel offers a good strength-to-weight ratio, which made them ideal materials for high-rise construction.

Unfortunately, concrete and steel do more than just hold a significant amount of embodied carbon. They also create urban heat islands, which is when concrete and asphalt absorb and reradiate heat throughout the day, making the surroundings hotter. In densely populated areas, wasted and dissipated heat from mechanical equipment further contributes to temperature rises.

In addition, almost all of us are guilty of turning on the air conditioning with a flip of a switch. Air conditioning units take in fresh air and expel warmer air, making the outside temperature warmer. Estimates suggest that air conditioning units are on pace to increase global temperature by half a degree within this century. Worse, most such units use polluting hydrofluorocarbons as refrigerants, are inefficient, drive up electricity demand and threaten power shortages during peak usage on hot days.