The design and cooling strategies we need now.
Our planet is warming. Every summer, extreme heat events take over the world, and every year they increase in intensity, duration, and frequency, killing more people than other climate disasters. The 2018 National Climate Assessment found that the frequency of United States (US) heat waves have tripled since the 1960s and that the average heat-wave season has increased by 45 days. The United Nations’ Intergovernmental Panel on Climate Change expects a similar global trend.
In March, a two-month heat wave blanketed India and Pakistan while record heat struck both poles simultaneously, despite the Arctic and Antarctic being in opposite seasons. In June, heat-trapping weather systems hit the US and Europe, setting all-time temperature records. The UK climbed over 40 degrees Celsius (104.5 degrees Fahrenheit) for the first time in history. The British government issued its first ever red-level extreme heat warning for several parts of England, including London. These extreme weather trends, exacerbated in cities by the heat island effect, poor bio-climatic building design, and expensive energy, make air conditioning (AC) unaffordable, particularly for many low-income families, leading to increased mortality and morbidity, especially amongst the elderly, even in wealthier countries. In July, on one Sunday alone, Portugal and Spain reported more than 1,000 heat-related deaths, while thousands of people fled wildfires in France.
Many buildings, especially in these once temperate locations, are still not designed for such conditions, and their inhabitants suffer. Even for those that can afford air conditioning, this is not the solution. The energy used by the air conditioner, unless it comes from a renewable source, will also add Green House Gas (GHG) emissions to the atmosphere, increasing the global warming effect and thus increasing the severity of subsequent heat waves. Global warming is further exacerbated by poor climatic design approaches, thermal and energy-inefficient building stock, and poorly drafted and policed energy codes.
Rapid population growth and urbanization have worsened the problem in less developed countries where vulnerable communities in informal settlements have proliferated. Many of the most susceptible also generate far fewer GHGs but suffer most, further fueling climate injustice.
Global warming requires buildings to be capable of adapting to more extreme temperatures while also reducing GHG emissions and the rate of related changes. Passive adaptation is not typically possible in many of our current buildings as these were designed to solve overheating problems by simply using more energy for mechanical cooling to achieve indoor thermal comfort. Even with a renewably powered electrical grid, buildings must now not only be energy efficient in design. Still, they must also be resilient because they ensure occupants’ thermal safety and comfort even when the grid fails. Utilizing low-cost, low-energy, passive cooling design strategies and features operating without or with minimal imported electricity can offer enhanced comfort and health with fewer running costs.
Nature-based cooling solutions play an essential role in both scenarios by distributing energy and providing zero/low-energy thermal comfort to cool the building when and where needed. They increase building resilience by allowing occupants to survive extreme weather trends in which the grid might fail and related disruptive events without mechanical cooling. Designers utilized many of these simple strategies in vernacular architecture for years.
Many buildings, especially in these once-temperate locations, are still not designed for such conditions, and their inhabitants suffer. Even for those that can afford air conditioning, this is not the solution. The energy used by the air conditioner, unless it comes from a renewable source, will also add Green House Gas (GHG) emissions to the atmosphere, increasing the global warming effect and thus, increasing the severity of subsequent heat waves. This is further exacerbated by poor climatic design approaches, thermally and energy-inefficient building stock and poorly drafted and policed energy codes.
Rapid population growth and urbanization have worsened the problem in less developed countries where vulnerable communities in informal settlements have proliferated. Many of the most susceptible also generate far fewer GHGs but suffer most, further fueling climate injustice.
Global warming requires buildings to be capable of adapting to more extreme temperatures while also reducing GHG emissions and the rate of related changes. Passive adaptation is not typically possible in many of our current buildings as they only solve overheating problems by simply using more energy for mechanical cooling to achieve indoor thermal comfort.
For example, shade, especially on windows, reduces heat gains to the building and the need for cooling. Through design, shade can block the heat while still providing daylight. Opening windows when the air is cooler outside, especially at night in dry climates, can cool the interior. The building can stay cooler for longer if combined with thermal mass in the interior and insulation in the exterior.
Air movement with fans can also provide thermal comfort in humid climates. So too, evaporative cooling in dry climates can cool outdoor or indoor air. At the same time, different types of living roofs can also increase biodiversity and provide natural cooling. Roof ponds transfer heat from the building to the night sky, just as living roofs bring biodiversity to the city and cool it down. The materials used in these buildings and their fabrication methods also affect our emissions.
Many materials we use in buildings are energy and carbon-intensive; they generate GHG emissions embodied in the building itself and have a significant impact. Therefore, it is essential to design buildings with materials that use less energy or, better yet, use carbon-sequestering materials such as responsibly harvested mass timber.
We must also remember the environment surrounding a building also affects indoor temperatures. Most of the world’s population now lives in a city and so are exposed to heavy construction surfaces like exposed asphalt that are continuously absorbing and releasing heat. Here we see the urban heat island effect and experience higher temperatures than outside dense urban environments. As designers of buildings and urban environments, we must design better environments. Buildings should possess features that keep them from overheating in most climates and are more resilient to climate change. These buildings’ designs incorporate strategies that keep them from overheating and even cooling, from smart shading and ventilation to micro-cooling devices integrated with green roofs, radiant and evaporatively cooled roofs, water-to-air heat exchangers, and variable ventilation green roofs.
The building becomes the air conditioner system and is shaped by the natural forces of the sun, the wind, and the earth until it becomes part of the natural environment. We have the tools to do this now and must act now.
