Our buildings usually remain comfortable during warm days because of constant air conditioning, sealed windows, and an assumption that power never fails. But as large parts of the country have learned, blackouts can hit at the worst possible moment.
When that happens, glass towers and sealed-off homes can quickly become stiflingly hot, showing why passive cooling methods are essential.
Ancient builders had no electricity, yet they made structures that protected people from the worst heat. Some devised thick walls that absorbed heat by day and released it at night.
Others planned entire neighborhoods to maximize shade. These time-tested ideas remain relevant for anyone who wants to stay cooler without cranking up the air conditioner.
This view is shared by Dr. Pablo La Roche, an architecture professor at California State Polytechnic University, Pomona, and sustainable design director at Arcadis.
With decades of research on passive cooling systems and low-energy architecture, his work highlights how historical construction techniques effectively addressed the challenges of harsh climates with intense summer heat.
Archaeologists have documented the Sumerians’ buildings in what is now southern Iraq. Walls made of mud brick or adobe were thick and had only small windows. This design helped reduce heat inside during the sun’s intense hours.
In some places, homes were built side by side, so fewer walls were directly hit by sunlight. The neighborhoods also included narrow streets that created cooling shade as people walked through the city.
That compact arrangement worked when indoor temperatures had to stay tolerable. Families gathered in inner courtyards where light and breezes could get in but the scorching rays had trouble reaching the seating areas.
Some of these principles might still be practical in hot, urban environments today.
Major power failures can be disastrous during a heat wave. In July 2024, the Houston area lost electricity for several days. When air conditioning shut off, many high-rises became uncomfortable in a hurry.
Some designers suggest that reintroducing features like operable windows, thicker walls, or rooftop shade structures might help with indoor temperature control and lower energy consumption at the same time.
Studies indicate that extremely hot summers are occurring more frequently. Placing more emphasis on passive cooling could reduce the stress on power grids and keep people safer when the grid goes down.
In ancient Egypt, builders knew that porous materials such as mud brick would block intense sunlight and slow the movement of heat indoors. Residents also slept outdoors on rooftops at night, taking advantage of the cooler air.
One striking invention was the mulqaf, which used a tall opening to catch breezes and push them downward into a building.
That airflow let hot indoor air escape through other vents. This system is still used in parts of the Middle East, where tall wind catchers provide fresh air without the need for electricity.
In the U.S. Southwest, the ancestral Puebloans built with mud brick and stone for many centuries. They placed dwellings close together and used smaller windows to limit excessive heat. Cliffs provided natural shade in places like Mesa Verde.
The layout took advantage of the sun’s angle to block the harsh summer rays and let in lower winter sunlight that warmed the interior.
These older methods still guide some modern builders who adopt adobe for its ability to moderate indoor temperatures.
Many cities today send rainwater away as quickly as possible through storm drains. Old societies in arid regions did the opposite.
During the eighth century, the Muslim caliphates in northern Africa and southern Spain put a high value on every drop of rain. Their structures often had systems that channeled water from rooftops and courtyards into underground cisterns. That water cooled patios and irrigated gardens during scorching months.
In other parts of the world, societies like the Mayans in Mexico built huge reservoirs to store the wet-season rainfall. Modern researchers are exploring ways to adopt or improve rainwater harvesting, especially in places threatened by droughts or limited water supplies.
Some architects believe that new designs should rely more on passive cooling and water collection. Orienting buildings in the northern hemisphere to take advantage of south-facing windows can help regulate heat gain and loss (International Association of Certified Home Inspectors).
Rainwater captured onsite can be reused for landscape needs, thus reducing the burden on public water supplies.
Larger cities that hope to reduce their energy usage and keep people safe during emergencies could integrate these techniques into upcoming developments. Some methods might look old-fashioned compared to modern high-rises.
Yet people who live in the world’s driest and hottest places have been testing these approaches for a long time, and their successes can offer strong guidance.
There is a growing call to learn from strategies that rely on local resources. Converting entire cities will take effort, but these ideas do not belong in the distant past.
There is a need to reconsider glassy towers and single-purpose rooftops, especially as blackouts become an increasing risk in regions experiencing more frequent heat waves.
Historical knowledge of staying cool in extreme heat could provide valuable solutions for maintaining comfort when air conditioning is not an option.
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