Indoor air movement can be controlled by careful positioning of openings in opposite directions, says architect Sathya Prakash Varanashi
Somewhere down the history, thanks to the invention of operable windows with shutters, we have forgotten all about walls with openings in them. These perforated walls, also called as jaalis in our region, can be seen in all Indian temples, Middle Eastern mosques, African huts or Cambodian monasteries. During these days of solid walls, this global use of jaali walls is only a reminder of a forgotten heritage and neglected green sense.
During the days when glass windows were yet undiscovered, masonry wall concept prevailed and the only option for providing openings was within these solid walls. Based upon the local material and climate, varied modes of creating the voids within the walls were explored, them playing an overarching role in the buildings. With modern ideas and glass shutters changing the design profession, jaalis were forced to the back seat.
Researchers have already proved that the indoor air movement can be scientifically controlled by careful positioning of openings in opposite directions following the principles of Venturi effect. The inlet and outlet sides are provided with varying sizes of voids to ensure air in the windward direction moves across the room out into the leeward direction.
Jaalis create climatic comfort also by reducing the solar glare inside. A typically large window gets so bright in our tropical sun that the rest of the room looks dark. The group of small openings in a jaali soften the light.
Cost saving is effected by reduced number of bricks required, reduction in mortar consumed, increased speed of construction and eliminating the need for much more costlier glass shutter windows.
Though perforated, jaalis could be either load bearing walls or partitions. Few manufacturers have been producing the inclined jaali blocks that provide complete privacy to the interiors, while many architects have also experimented building the wall block itself in an angle, such that no rain penetrates and direct view is avoided. The mason may have to take extra care not to unnecessarily spill mortar or pack the joints beyond the need. Alternately, it is possible to buy the jaali block made with clay or cement. Subsequently, the task of jaali building is like any other wall construction — only the regular brick is replaced by the jaali block.
Jaali walls are still found in all village settlements, for all core and ancillary facilities like house, school or the production shed. The city contexts may limit the use of jaalis due to proximity of houses or apprehension about security when all the residents work, leaving the place locked the whole day. However, jaalis are yet an eminent possibility even in a city, especially in public buildings like schools, institutions or government offices. Also, residential walls enclosing ancillary areas like wash, utility, taller wall tops, family spaces, and such others can have jaalis, beautifully contrasting with the rest of solid walls.
(The writer is an architect working for eco-friendly designs and can be contacted at firstname.lastname@example.org)