In the middle of summer the heat can be unbearable. With innumerable power cuts the little relief that  ceiling fans afford while turning at high speed is denied too. Is there no way to reduce the dependence on electric fans? Or at least reduce the dependence on the electro-mechanical ventilating and cooling systems like air conditioners?
The answer is yes, provided we give the fickle minded devil - the weather it's due! During the summer months we get cool breeze essentially from the South and West. Whereas it is a little difficult to control the sun and heat entering the house from the West through the windows, it can be quite easily controlled in the South. By merely having big windows in the South, lots of cool air can be got into the house provided we also have some openings in the North or East for this air to pass out, carrying the heat to the outside. During the summer months the air pressure will be less in the North and East directions compared to the West and South. By strategically placing windows on opposite or adjacent sides of air entry, cool summer breeze can be made to pass through the house.(See figure)

Natural ventilation v/s artificial  ventilation
Apart from saving energy bill, natural ventilation provides safe, fresh, cool breeze that is at the right temperature and speed. Many times it is found that the fans run too fast drying the mucous membranes of the respiratory system and cause nasal blocks and dry throats. Some people get dry coughs if they stay under fans for any length of time. Whereas ceiling fans churn in the same stale air again and again inside the room natural ventilation causes frequent air changes by bringing in the cool breeze which is fresh from outside.
Another advantage of natural ventilation is that it is not a continuous stream.
There are natural breaks when the body can adjust to the changing air temperature and humidity. It is advisable for those sensitive to sudden changes in air temperature and humidity, not to keep their beds directly in the flow of the breeze. During some seasons, there will be too much of climatic variations during the night, when they are sleeping and they may not be in a position to get up and reduce the air flow by closing some of the shutters of the windows. Too much of cold draft of air, passing over a sleeping person may cause some discomfort in the morning.
Even though in summer, the general breeze direction is from south and west,as the south-west monsoon starts in summer months, it does not set immediately. Due to local variations, cyclones and turbulence the summer breeze may be blowing from the opposite direction some time, but by and large it blows from the south and west.
Summer monsoon, incidentally is not just the three months of actual summer, but it also includes the rainy season immediately after summer. In fact in India, monsoon usually means the South-West monsoon rainy season, during which, even though it rains, the in between period can be quite warm and humid Therefore it becomes essential to provide suitable sun and rain protection devices for all openings in the south and west, other wise the benefits of cool summer breeze entering the house may be cancelled by the rain and sharp afternoon sun entering the house.
Once we provide big windows in the South and West, with suitable sun and rain protection devices, it becomes equally important for this breeze to go out carrying with it all the heat from inside the house.
Hot air can be sent out by providing smaller openings in the East and North. Smaller openings in the east and north are sufficient to draw off the breeze entering the house from the South and the West, since the breeze will be at higher pressure in these directions and naturally it will easily flow towards the East and North as these are at low pressure compared to the South and West.

Ventilation requirement of different rooms
Of all rooms, providing suitable natural ventilation for the bed room of adult couples is very important. Here the special requirement is that we have to provide the privacy along with window openings for good cross-ventilation. The adult couple lead an active life and the heat generated needs to be taken off and they naturally prefer a well ventilated cool room. This becomes more complex as we have to maintain privacy too at the same time. It is comparatively easy to cross ventilate or make the breeze flow through or cross the children's room or elderly couple's room. Children and elders may not close their bedroom doors and curtains will ensure what little privacy they need. Infact children and elders expect the adult members to be within calling distance and this is easily done in a room where the door is not closed and curtains ensure privacy.
We can beat the summer heat,the natural way provided we take care of all known physical aspects like summer breeze direction, difference in air pressure around the house and the heat gain from the direct rays of sun.