In a hot and humid climate such as in Kerala, wind direction is the most critical factor that gives thermal comfort to a person. Afternoons at the beach during summer does not feel hot because of the breeze there. Even though the temperature is high, the wind movement can make you feel comfortable. So, this movement of wind or cross-ventilation is a very important criterion for designing buildings in hot and humid climates. This blog examines the importance of natural cross-ventilation in houses, and also offers some techniques to incorporate it further in the planning of houses.
Proper Placement of doors and windows
When I think of proper natural cross ventilation in buildings, Padmanabhapuram Palace comes to mind. It is the best example of traditional Kerala architecture. I think about the innumerable number of courtyards it has and I realized that buildings can be made do without any windows by using the various designs of timber jallis.
The sill level of the openings can start closer to the floor level so that when one lies down on the floor, the wind blows and embraces them. Natural ventilation has to be brought to the floor level in places where people would sit down on the floor. When one follows the normal sill level of two or three feet for placing the windows, the wind does embrace a person sleeping on the floor.
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One common mistake seen in houses is that large window openings will be given on one side of a room, while the other side will have none at all. As a result, there will be no wind movement. (See Illustration 1- cross ventilation).
The plan of the building has to be designed in such a way that the doors and windows face the direction of the wind to allow for maximum natural cross-ventilation (See Illustration 2). The wind direction in Kerala is from the southwest for major portions of the year. It changes in the northeast direction during the months of October and November. Therefore, openings have to be provided in the north-east and south-west directions for free flow of air throughout the year.
Use of Courtyards in House
In traditional Kerala houses, the central courtyard is the natural ventilation system (See Illustration 3).
The typical plan of stacking rooms one behind the other is avoided when a courtyard is introduced in the plan. They can help in bringing in more natural light and air. They also ensure that properly designed openings can be given to enhance cross ventilation in houses. However, the use of courtyards is decreasing as people feel the safety of the house may be compromised because of it.
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Roof Gables in Kerala Houses
One physics lesson from school that is useful in designing climate responsive buildings is the concept that the lightweight hot air rises, while the cool air flows in to replace it. This is how the sea breeze and land breeze are caused. The timber roofs in traditional Kerala houses have roof gables (Mukappu) through which hot air can escape and the cool air blows in to replenish the space. This natural wind movement is the reason why the old Kerala houses were cooler. (See Illustration 4).
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To Conclude
Cross-ventilation helps in improving the thermal comfort of a house by maintaining the minimum air quality, reducing heat and other pollutants, and allowing natural airflow. The size and placement of doors and windows have to be given importance when designing a building. They should be incorporated right from the first stage of design. The sizes of the openings can be larger, and closer to the floor for maximum comfort. They should be placed along the wind direction to make sure air moves in and out of the house freely. Therefore, regardless of the place, natural cross-ventilation in houses is as essential as breathing is to humans.
(This is an article that I wrote for a Malayalam magazine a few years ago, but getting published in English for the first time.)
