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The authors are researchers from the Climate Change Health Effects, Adaptation, and ResiLience (HEAL) cluster at the University of British Columbia.

Record-breaking temperatures are sweeping Europe and North America, a grim reminder of last summer’s deadly heat dome in British Columbia. Increasingly, it seems our cities are just not built to withstand this intense heat.

Until last summer, Vancouver and much of the West Coast of Canada was able to remain convinced of its historical climate gifts. While the area gets hot from time to time, it’s nothing like the heat in the East, right? After all, this is one of the last wealthy regions of the world yet to adopt building air-conditioning en masse, at least outside of Europe.

That’s why the City of Vancouver’s move to mandate mechanical air cooling in all new multifamily homes as of 2025 is particularly concerning.

We know that air conditioning is important when it’s above 40 degrees Celsius outside, but there is a wide array of heat-mitigation measures that are more cost-effective and more conducive to creating healthier buildings and cities, especially given that such heat extremes will be infrequent in Vancouver. In its urgency to address an extreme scenario, the city has missed an opportunity to improve public health while increasing urban climate resilience.

Typical air-conditioning retrofits to existing residential buildings include installing window units or ‘mini-split systems’ that will only recirculate indoor air – in fact, they can reduce the amount of fresh air received indoors to near-zero. New buildings can mitigate this with more complex ventilation equipment and control systems, but this comes at a premium that can require cost-cutting in other areas of a project.

In the 1990s, health scientists and engineering researchers coined an illness called Sick Building Syndrome, which was found to affect millions of office workers in North America who carried out their careers in buildings that, while well “air-conditioned,” received poor natural daylight and very little fresh air.

The great solution to Sick Building Syndrome turned out to be a set of building design measures that are likely of surprise to no-one: if you place humans in an indoor space with more direct fresh air, daylight and vegetation, we actually become healthier. Government policy has traditionally played a vital role in ensuring this is reflected in our building codes and it is worrying that a mandate to install air conditioning in new residential buildings was introduced in absence of any tangible mandates for creating overall healthier, climate-resilient buildings and communities.

Air conditioning is also not a solution for a ‘net-zero’ future. Indeed, Singapore, a country whose founding father once called air conditioning the greatest invention of the 20th century, has launched several major projects since 2018 to mitigate urban overheating and reduce energy use for air-conditioners.

In Spain and Italy, buildings have been designed for decades with features that naturally mitigate the effects of heat, such as outdoor shutters over windows. This year, the countries enacted new energy conservation measures that ensure indoor spaces cannot be cooled below 27 degrees Celsius. Vancouver, however, has set 26 degrees Celsius as the maximum allowable indoor temperature of future homes, a threshold with poor scientific consensus. In countries with experience of hot climates, emerging policies are focused on reducing reliance on air conditioning. Ironically, Vancouver just set its course in the opposite direction.

If we are to survive and hopefully thrive in a warming world, we need our policies to promote many cost-effective solutions with multiple benefits, not mandate only one technology. Alternative technologies for cooling such as radiant systems are a start. These rely on cooling the interior surfaces of our buildings instead of directly cooling the air, providing a similar degree of comfort with much lower energy requirements.

We also need to prioritize cost-effective passive and ecological forms of cooling that have already been tried and tested elsewhere: our building surfaces and roads need to be renovated with materials that reflect more of the sun away. Our buildings need to be designed to promote better nighttime cooling via natural ventilation. And we need shading on the exterior of our buildings, including from trees.

Further, every neighbourhood needs at least one outdoor space that remains cool and can serve as a refuge when temperatures are high. These spaces also provide additional, year-round benefits to citizens as locations for stress reduction and social engagement. Our research has clearly demonstrated that areas with greater natural vegetation have healthier residents.

We need to rethink how we integrate urban trees into cities, prioritizing them and ensuring that they too survive the increasing pressures of climate change. This involves protecting the existing urban tree canopy during development, engaging in pro-active management to keep trees healthy, planting trees in low-canopy and heat-vulnerable neighbourhoods and engaging residents in tree stewardship through activities such as planting and watering, keeping trees healthy while reaping the benefits of contact with nature. Unfortunately, Vancouver has recently weakened its tree-protection bylaws, prioritizing housing over urban nature.

Cities in Canada need to rethink their action plans when it comes to extreme heat. Any mandates for mechanical cooling such as air conditioning in future or existing buildings must be paired with sensible requirements for passive building design, urban forestry and related climate adaptation measures to cool our cities both indoors and out.

If the global heat waves of the past two years have shown us anything, it’s that we have only one chance to do this right.

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