Cooling the Crisis: The Environmental Impact of Air Conditioning
In Hamilton, the average number of days per year with temperatures over 30°C is expected to more than double in the next 30 years, rising from 16.2 days to 37.2 days of extreme heat (1).
These extreme temperatures lead to higher mortality rates from heat-related illnesses such as heat exhaustion and heat stroke. Vulnerable populations, including the elderly, children, infants, the ill, the homeless, low-income households, and outdoor workers, are particularly at risk (2). High temperatures are also linked to community mental health issues, increased violence, and poorer educational performance (3).
Globally, this consistent warming trend is driven by human activities that contribute to the climate crisis.
The Role of Air Conditioning in Climate Change
Modern cooling technologies like air conditioning aim to address heat-related problems, but many are unaware of the significant role they play in exacerbating the problem. The widespread use of air conditioning contributes to rising global temperatures.
North America is over-reliant on air conditioning, with usage disproportionately high compared to the actual need. While only 9% of the population in North America requires cooling infrastructure based on climate, 78% had air conditioning in 2022—more than any other continent (4). However, communities have been managing unsafe heat levels for centuries using sustainable methods that are still relevant today.
The Negative Environmental Impacts of Air Conditioning
Greenhouse Gas Emissions
Air conditioning runs on electricity, which may seem like a clean, endless resource. However, electricity is often a mix of various energy sources, including coal, natural gas, hydroelectric, wind, and solar. In Ontario, gas or oil accounts for an average of 27% of the energy mix (5). Therefore, the electricity used to power air conditioners (ACs) partly comes from natural gas combustion, which generates greenhouse gases (GHGs).
During heat waves, when electricity demand spikes due to increased AC usage, natural gas power plants are used to meet this demand, further increasing GHG emissions. Most ACs are not very efficient, consuming more electricity than necessary to cool the air. In fact, the average AC is only half as efficient as the top-of-the-line models (4). These inefficiencies make air conditioning an energy-intensive process. In 2019, air conditioning was responsible for 1 gigaton of CO2 emissions (6).
Unsafe Refrigerants
AC technology relies on compressing and expanding a volatile compound known as a refrigerant, which absorbs and releases thermal energy. Typical refrigerants used in ACs are hydrofluorocarbons (HFCs), which have a global warming potential (GWP) between 12 and 14,800 times greater than CO2 (7). HFCs can escape into the environment through leaks or at the end of a product’s life, making them extremely potent contributors to global warming. Even if HFCs are less prevalent than CO2 they are much more potent.
Feedback Loops
Air conditioning is part of a negative environmental feedback loop. As global temperatures rise, AC usage increases, leading to more GHG emissions and further warming. This cycle perpetuates itself, especially in densely populated areas.
Even if the electricity used to power ACs were entirely renewable, this feedback loop could still occur. ACs remove heat from indoor spaces and expel it outside, raising local temperatures. This can result in increased AC usage, further perpetuating the cycle.
This feedback loop exacerbates the “urban heat island effect,” where cities experience elevated temperatures due to heat-absorbing materials like asphalt, closely packed buildings, and a lack of green spaces. Studies have found that heat emitted from ACs can increase urban surface temperatures by 1°C at night (8).
Tackling the Problem: Sustainable Solutions
Fortunately, there are many low-energy alternatives for managing heat.
Nature-Based Solutions
Vegetation can cool surrounding areas through shade. Trees absorb solar radiation and use it for photosynthesis, with only 10-30% of sunlight passing through their canopy in the summer (9). This cooling effect benefits surface air and buildings. Strategic tree planting to shade windows can significantly reduce energy use. Vines can also provide vertical green facades, offering coverage in tight spaces.
Vegetation also cools through evapotranspiration, where water is released into the atmosphere, producing a cooling effect as heat energy converts liquid water into vapor. Suburban areas with mature trees are 2 to 3ºC cooler than new suburbs without trees (9). In direct sunlight, vegetation can reduce temperatures by as much as 20°C in hot climates (10).
Examples of trees that thrive in Ontario and provide substantial shade include hackberry, Freeman maple, and red oak (11).
Building Science Solutions
There are many strategies to enhance your home’s natural cooling ability without major renovations:
- Close blinds or curtains on sun-facing windows during the day.
- Open windows at night to allow cooler air in and close them in the morning as temperatures rise.
- Create a cross-ventilation effect by opening the lowest window on the windward side and the highest window on the leeward side.
- Use fans as an energy-efficient alternative to AC.
- Turn on oven hood fans when cooking to expel heat.
These simple solutions can cool your home by several degrees during the summer months. If you do use AC, the International Energy Agency (IEA) recommends setting it no lower than 24-25°C to maintain a safe temperature without straining energy systems (12). Lowering the AC setting by just 1°C can increase annual AC energy consumption by 12-18% (13).
Improving your home’s airtightness and upgrading to ENERGY STAR-certified windows can also prevent cool air from escaping.
The average Canadian home has the equivalent of a 40 cm diameter hole due to cracks and gaps (14). Air sealing, such as caulking and weatherstripping, can help keep treated air inside for longer.
ENERGY STAR-rated windows specify their heat transfer rating (U-factor) and the solar heat gain coefficient (SHGC). Choosing windows with low U-factors and low SHGC can reduce the amount of heat entering your home.
Green Venture offers Home Energy Assessments where our Registered Energy Advisors (REAs) inspect your home for energy inefficiencies and provide personalized recommendations to help you reduce your energy consumption.
Sources
- https://climateatlas.ca/map/canada/plus30_2030_85#z=8&lat=42.88&lng=-80.12&city=451
- https://www.canada.ca/en/health-canada/services/climate-change-health/extreme-heat/who-is-at-risk.html
- https://climateatlas.ca/health-impacts-extreme-heat
- https://www.unicef.org/innocenti/cooling-dilemma-amid-climate-change
- https://www.ieso.ca/Learn/Ontario-Electricity-Grid/Supply-Mix-and-Generation
- https://discovery.ucl.ac.uk/id/eprint/10150633/1/Mumovic_256-6100-1-PB.pdf
- https://www.canada.ca/en/environment-climate-change/services/climate-change/greenhouse-gas-emissions/quantification-guidance/global-warming-potentials.html
- https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013JD021225
- https://www.epa.gov/sites/default/files/2017-05/documents/reducing_urban_heat_islands_ch_2.pdf
- https://coolcalifornia.arb.ca.gov/how-cool-vegetation-works#:~:text=Evapotranspiration%20includes%20the%20evaporation%20of,and%20thus%20cool%20the%20air
- https://www.regionofwaterloo.ca/en/health-and-wellness/resources/Documents/ShadeTree_List.pdf
- https://www.cbc.ca/news/science/air-conditioners-sustainability-heat-1.6914054
- https://qz.com/1695582/how-to-use-the-air-conditioning-without-ruining-the-environment
- https://natural-resources.canada.ca/sites/nrcan/files/canmetenergy/pdf/housing/fixtheholeinyourwall.pdf
