You are assuming that you don't need an aircon at night. Something that's very much not the case during a multiday Australian heatwave.
Despite a fan pointed right at me I’d awake every morning with a sweat soaked mattresses…
Source: In brisbane and lived in the north.
No, this is Australia. Houses are more like tents than actual buildings.
Pre-AC being ubiquitous (or being invented), the way for people to cool off in summer was to have airflow. Insulation was a more of a cold climate thing, as keeping the heat in / cold out was more intuitive when burning wood or coal: thermal boundaries were more 'needed' when there was snow outside.
Having thermal boundaries in your structure didn't make sense when it was as hot inside (due to lack of AC) as it was outside, and it has only been in recent years that people clued into that fact. But unfortunately there's a large stock of housing around that was built pre-clue in.
Even now there are people who insist that houses need to "breathe", i.e., have holes / be drafty. They do not:
* https://www.energyvanguard.com/blog/Myth-A-House-Needs-to-Br...
* https://www.greenbuildingadvisor.com/article/most-houses-tha...
* https://www.greenbuildingadvisor.com/article/buildings-dont-...
Buildings need to be as air tight as possible, and be ventilated through mechanical means so that stale air is vented out and fresh air is brought in after being filtered and tempered (via an ERV).
Perhaps in California, Australia or other desert areas. The pacific northwest had major issues when OSB met the concept of "air tight" housing. No airflow in/through walls leads to condensation, mold and collapse of many "engineered" wood products held together with glue.
These are not indicators that air tightness is bad, but rather that people don't understand building science. Washington state (for one) has mandated air tightness levels (§R402.4.1.3) and testing (§R402.4.1.2):
* https://sbcc.wa.gov/sites/default/files/2023-04/2021_WSEC_R_...
Air tight passive houses are built without issues in the US PNW:
* https://hammerandhand.com/high-performance/passive-house-bui...
* https://asiri-designs.com/f/how-to-design-an-energy-efficien...
The province of BC is mandating near-passive house levels of air tightness:
* https://www.energyadvisor.pro/airtight-energy-advisor-contac...
* https://energystepcode.ca/how-it-works/
* PDF: https://www.bchousing.org/publications/Illustrated-Guide-Ach...
Build your structure according to how physics works and it will work just as well from the tropics (IECC Zone 1) to the arctic (IECC Zone 8):
* https://buildingscience.com/documents/insights/bsi-001-the-p...
* https://basc.pnnl.gov/images/iecc-climate-zone-map
Air tightness is coming to building codes everywhere, and if you can't make it work then you shouldn't be building because you are incompetent:
* https://www.iccsafe.org/building-safety-journal/bsj-technica...
...also I doubt anyone from e.g. Brisbane would need to be told about mold and condensation.
Modern A/C was invented in 1901, and A/C penetration in Australia is not that far behind the US.
But much as in Texas where houses are also made of paper and cardboard, cheap energy has made forcing temps down via AC much simpler (for property developers).
I'm not saying that to be snarky, I would generally love to know. I live in a moderately cold climate (England) and I often wonder how people here survived through the winter before the comforts of modern technology. And England's not that cold - how the hell did indigenous Canadians do it, for example? Did people just shiver by a fire for months at a time?
EDIT: I didn't think I was being snarky in my original final sentence, but to avoid misunderstandings I've removed it.
I think there are two main things at play: buildings used to be built differently, and yes, people prefer not to suffer these days.
Old Australian buildings (e.g. "Queenslanders") were often built on poles to let the air circulate underneath, they'd have the roof extend far over windows to stop sunlight (and heat) getting in. Those are not the most enjoyable places to live in, these days people prefer a bit of sunlight during the day, and a constant draft is not pleasant in winter.
And yes, I imagine people just didn't sleep all that well and spent heatwaves sitting around in the coldest spot in the house waiting for it to be over. These days people want to sleep well throughout the year and want to be productive even during heatwaves.
Also: wood stoves large and small can pump out a lot of heat. You can kick up the small tin metal camping stove and make your canvas tent 75 degrees, dry out any wet clothes. Likewise, a large iron stove can make a room boiling. After all, saunas - in one form or another - are a common feature of northern cultures.
You'll also find westerners accustomed to air-conditioning who live there and have "adjusted".
It takes about 2 weeks and your body makes some sort of adjustment.
It's an interesting phenomenon that maybe someone here can comment on more fully. By that I mean what exactly is happening to us when we adjust? Is it purely psychological or are there actual biological changes/effects at play? Whatever it is you really do "adjust" and it's not that bad after a few weeks. You even learn to sleep well at night in sweltering heat...again after you adjust.
Of course there are limits but we're built to handle the heat.
A lot more people live out in cheaply built homes with small, barren yards and dark roofs that are literally designed for air conditioning. Older homes often have better airflow.
An example of a newer suburb in Sydney is Marsden Park: https://www.youtube.com/watch?v=WzV3H_K73To
I don't use/have aircon in my home in Brisbane and I get by fine :) Although it is nice to have aircon in the summer when I'm working on the computer and need to concentrate (my office at work is air conditioned, like most).