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Natural Ventilation

 As the weather is getting warmer, it is a good time to look into how to make our spaces cooler and more comfortable for summer. For centuries, people in Africa, the Middle East and other hot climates have developed ingenious ways of ventilating their spaces and cooling the air that flows through their buildings. Traditional ways of building in these hot climates include building rooms around a courtyard, often with a water feature and vegetation in the courtyard to cool and refresh the air. Their streets were traditionally very narrow, so that one building would shade its neighbour, preventing heat buildup. Their buildings were crafted from clay with very thick walls and roofs to  keep the rooms cool, and they often included wind catchers that act like chimneys to draw the air through their buildings.

Windcatchers on the rooftops in Iran
Creative commons licensed from https://es.wikipedia.org/wiki/Captador_de_viento

But how can we capitalise on these traditional ideas in our own homes, so that we don't need energy guzzling fans and airconditioning? The first thing to understand when looking at natural or passive ventilation is how the air flows in a room. If you have the window directly in line with the door, it tends to create a tunnel of air, leaving most of the room unventilated, resulting in a hot and stuffy space for most of the room. If you have a choice of windows to open, use one diagonally opposite the door - this will also reduce the funnelling of the air that can be quite draughty. Now the air can flow into all the corners of the room, as you can see in my diagram here.

Air flow depends on the position of openings

If you have a room where the window is directly opposite the door, you can adapt it slightly by hanging the door with the hinges on the other side, so if the door is half open, the fresh air will be channelled to the opposite corner. It is best to call in a carpenter to do this, as it can be quite tricky to re-hang a door so that it opens and closes smoothly.

We can also capitalise on the principle that hot air rises - the cool air will enter the room at a low level, and as it heats up, it will tend to rise. This is why you find many homes have fanlights, so the warmer air can escape. In summer, it is good to keep all the fanlights (to windows and above the doors) open day and night to keep the rooms well ventilated.

Cool air comes into a room at a low level and rises as it heats up

Another way to help cool a room is with the addition of pot plants - the air is cooled through evapotranspiration, as well as evaporation from the soil and drip tray. A favourite is succulents, which are also excellent at removing carbon dioxide from the air and replacing it with fresh oxygen. They are also very resilient to drought, so if you go away for a few days or simply forget to water them, they survive very well. 
My little family of succulents

Another method that uses evaporation is to have water in a porous (unglazed) ceramic pot close to an opening. The water is drawn to the outside of the pot where it evaporates, and lowers the temperature of the room. This is a method in common use in North Africa and the Middle East, and there is evidence of its use around 800CE in the palaces on the east coast of Africa. You can use a ceramic wine cooler to get the same effect - place it near a window so that the sun can heat it up for maximum effect.

An unglazed ceramic wine cooler



 

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