Throughout history, humans have required comfortable temperatures to survive. Despite being able to temporarily survive in extreme temperatures, the estimated ideal temperature for a resting human sits around 21C, with a rough comfort range of 10C to 30C. But how did humanity keep their homes at a comfortable temperature, despite the hugely varied climates we have settled in?
No matter where we are in the world, it is true that night time temperatures drop, and that cooked food is a crucial part of survival. Therefore, the most obvious example of increasing temperatures is the use of fire. While being an important source of heat required for cooking food, fires also heat the area or rooms around them. This was often just an open fire but was sometimes a brazier or central hearth.
Many civilizations refined and improved the use of fire to heat their homes more efficiently. The ancient Koreans and Romans independently discovered that by raising the floors of their buildings above the ground, they could effectively channel the warm air and smoke of an external fireplace underneath a masonry floor. The hot air is pulled through the underground space by having a chimney on the other side of the building from the fireplace. The result is that the masonry floor radiates the heat into the building, keeping everyone warm.
At the cooler end of comfort techniques, the Ancient Egyptians used reeds or cloth soaked in water to cover their windows. Wind would blow through the windows, cooled by the water, and cool the inside of the building. There are even examples of paintings that showed slaves fanning clay pots filled with water, which not only cooled the air but also added moisture to the air, improving the comfort of the building occupants in the dry climate. These are both examples of evaporative cooling, where water evaporation absorbs large amounts of heat to evaporate.
Ancient Egyptians and Persians also used windcatchers, which ventilate buildings by relying on wind to pass through a space and cool the occupants. Similarly to the Roman and Korean methods for heating, this requires external openings (an inlet and an outlet) to allow the air to enter and exit. A variation of this that negates the issue of wind being an unreliable source is known as stack ventilation, whereby the inlets are placed at ground level and the outlets at ceiling height. The warm air rises and exits, while cooler outside air enters from below. The cool air of night time is also used in a technique called night flushing, where windows are kept closed all day and then opened in the cooler night air.
The Persian windcatchers were used in addition to a system known as qanat. Near-horizontal underground water tunnels were connected to underground reservoirs or aquifers. The water was then transported over many kilometres by gravity, eventually used for agricultural purposes. Along the way however, the numerous well shafts could be used with a wind tower to draw warm air in. The shade of the tunnels keeps the water cool, and the warm air that passes over it is cooled as well. This could then cool basements for food storage and or homes. This system spread from ancient Persia to other arid regions. Even today, the qanat system is being trialled in Seville as an alternative modern day air-conditioning solution.
In the modern age, we have advanced computer simulation software and powered mechanisms to help buildings and occupants be kept at a comfortable temperature. Building Management Systems such as HeatingSave can help keep temperatures comfortable autonomously with precise thermometers, exact and timed control of heating or cooling machines, and complex algorithms to adapt to changes in routine or heat loss profiles. It's incredible to think that humans invented, designed, and built so many varied and complex technologies to help keep themselves comfortable, and often found similar solutions to shared problems despite vast distances between them!