IMPORTANCE OF CROSS VENTILATION in Hot Humid Climates
Cross-ventilation is very important criteria for designing buildings in hot humid climates like in Kerala.
When I think of cross ventilation, I think about Padmanabhapuram Palace which is the best example of traditional Kerala architecture. I think about the innumerable number of courtyards that it has. I realised that we can do buildings without any windows using the various designs of timber jallis. The openings start at the floor level so that when one lies down on the floor, the wind blows and embraces you. Ventilation has to start at the floor level if one is designing buildings where people lie or sit down on the floor. When one follows the normal sill level of two or three feet for placing the windows, the wind does not embrace a person sleeping on the floor.
In a climate such as in Kerala, where it is humid, wind movement is the most critical factor that gives thermal comfort to a person. Even in the peak summer, at noon, if you are at the beach where the wind is blowing, one does not feel hot because of the wind movement. Even if the temperature is high, the wind movement can make you feel comfortable.
For cross-ventilation, it is important that openings have to be provided in windward direction (for the wind to get in) and in the opposite direction also for the wind to get out. Both the windward side opening and leeward side opening shall be of the same size. This might be one of the reasons that in the old houses, opposite a door, another door or window openings were provided.
One of the common mistakes that people make is that large window openings are given on one side of the wall. If there is no opening for the wind to get out, there will not be any movements. (See Illustration 1). But the plan of the building has to be made in such a way that openings can be given at the right locations so that wind can get in and get out, then there will be cross-ventilation (See Illustration 2).
Also for a major part of the year in Kerala, the wind comes from the south-west direction. So you have to give openings in the north-east direction also for the wind to get out. During the October November months, this is reversed where the wind blows from the north-east direction.
"Vishram by the sea". Click to visit the project.
Use of Courtyards
In a traditional house with a courtyard, the courtyard helps in cross ventilation (See Illustration. 3)
The typical planning of one room behind the other is avoided when the courtyards are introduced as a design element. There is more natural light and the properly designed openings can enhance cross ventilation. The reason given by some clients is that when there is a courtyard, the safety is compromised.
Roof Eaves in Kerala Buildings (May Be Put in a Separate Box)
I think one of the basic lessons in school Physics which is very useful as far as the design of many of the buildings is concerned is that the hot air is lighter and rises, while the cool air blows in to take its place. This is how the sea breeze and land breeze are caused. The traditional Kerala roofs have the roof eaves (Mukappu) through which hot air can escape and the cool air blows in to take its place. This creates the wind movement in the houses and this is one of the reasons that the old houses were cooler (See Illustration 4).
"Vishram by the sea".Click to visit the project.
(This is an article which I wrote for a Malayalam magazine few years ago, but getting published in English for the first time.)