Yatin Pandya on 'jaali' as a traditional element

Sunday, 16 October 2011 - 5:34pm IST | Place: Ahmedabad | Agency: DNA
The author, a city-based architect and historian, talks about the effectiveness of Jaali

In today's times when green movement is being hijacked by select manufacturing lobby and the array of service providers with tools, norms and parameters drawn from the west, it is imperative to look into our own backyard and review what tools and strategies did architecture of the place applied for centuries. A look at the vernacular/traditional architecture reveal that these built forms have proven their performance over centuries in terms of combating environmental conditions with least or no electrical energy spent for the same.

A number of architectural elements have contributed in respective regions to arrive at comfort conditions with optimisation of material resources and energy consumption. Jaali is one such element of architecture that has been an effective tool in addressing environmental comfort.

Jaali as small perforations in a wall has been versatile enough to prove effective in hot dry as well as hot humid climate zones. Jaali manages to cut down on direct sun and thereby the heat ingress. It also allows movement of air for cross breeze and ventilation. Jaali breaks down total square metre of consolidated aperture area of a typical window into number of small holes. The holes are nearly of the same size or often smaller than the thickness of the material it is built with. This means each void is a cubical proportion of height equal to depth, protecting ingress of direct sunrays and haze as well as glare associated with it, for most of the sun angle through the day and across seasons.

It only cuts the glare but lets illumination through, not affecting the intensity of light. Similarly even view across the aperture is maintained. In fact, it makes the view more convenient to Indian notions of privacy. From within, everything outside is visible through Jaali holes but from the outside, nothing gets visible inside due to light difference. This best suited privacy notions and therefore was synonymous to Rajput and Islamic architecture in Middle Ages, the era of defence.

Not only does it work for light, sun and view, it also works scientifically for wind. Both Bernoulli as well as Venturi laws apply effectively through the Jaali. When air passes through smaller aperture, its velocity increases. Thus there is a perceptible presence indoors even with a mild breeze outdoors. This improves efficacy and provides a deeper penetration. Principles of physics also suggest that when air is compressed and released it becomes cool. This is similar to an air-conditioner where compressor, as the name suggests, compresses the air and releases the same through microholes. Thus, Jaali, in micro ways, helps cool the air by passing the same through small holes.

Jaali was an effective element replacing modern day glass for a transparent view and yet improving on the glass by controlling glare and heat and allowing breeze. The proportion of holes was larger and the overall percentage of opacity lower in the humid climates like Kerala and Konkan compared to the drier climes of Rajasthan and Gujarat.

Thus, glamour of glass for uninterrupted view is not a new phenomenon. Jaali achieved the same with better aesthetic grace as well as environment management within socio-cultural denominations of privacy and security.

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