Cities cannot outrun hotter climates with air-con alone
Air conditioning units flying off the shelves worry Australian urban heat expert Mat Santamouris.
With 10 systems being purchased every second worldwide, a University of NSW professor fears cooling technology will become the default response to rising global temperatures.
“We can’t weather our way out of climate change,” he said.
“If every building depends entirely on mechanical cooling, we’re adding even more heat to our cities while putting tremendous pressure on electrical systems.”
40C days in generally temperate European cities have brought urban heat into focus, with more frequent and severe heatwaves linked to rising atmospheric greenhouse gas concentrations.
In Australia, an El Niño, alongside a global temperature rise, could lead to harsh summer conditions, especially in heatwave hotspots such as western Sydney.
Because man-made materials such as asphalt and concrete absorb rather than reflect solar radiation, cities are plagued by higher temperatures that are worse than surrounding farms and forested areas.
Professor Santamouris says cities can benefit from passive cooling strategies that prevent heat from entering buildings, such as ventilation and sunlight-reflecting roofs, according to a global review by academic and RMIT’s Konstantina Vasilakopoulou.
For example, research suggests that widespread use of “cool roofs,” which reflect solar energy through design, color, and material selection, could reduce urban ambient temperatures by about 1-2 degrees.
Heat-reflecting roofs can reduce peak electricity demand for cooling by 30-40 percent; This is key to keeping bills lower for all users as the cost of operating networks is lower if the maximum electrical load is minimized.
Higher electricity demand also leads to higher greenhouse gas emissions; because fossil fuels are still the main generation sources for most grids.
Passive techniques, which are often inexpensive, can further reduce the mechanical cooling load, which is vital for low-income households.
Despite their benefits, Prof Santamouris says awareness of non-mechanical cooling technologies is limited and air conditioning remains the default response in many parts of the world.
“Buying an air conditioner is the simplest solution,” he told AAP.
Prof Santamouris says that although it is a life-saving and critical technology, air conditioning should be seen as a last line of defense against climate change rather than a first line of defence.
“We need a holistic systems approach that starts with climate-responsive building design, shading and better materials, then uses the most efficient cooling technologies only when they are truly needed.”
Building codes and planning policies represent opportunities for policymakers to promote passive cooling design.
In Australia, initiatives to tighten energy efficiency and other environmental requirements may face opposition from interests seeking to ease housing shortages with rapid new supply unhampered by regulations.
Prof Santamouris said failure to proactively deliver climate-adapted homes and cities would cost much more in the long run.
“We must protect our buildings. We must protect our people.”
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