What is the function of cross-ventilation fins or jaalis in tropical architecture?

• A. Block wind entirely.
• B. Allow airflow while maintaining privacy and security; reduce glare.
• C. Solely decorative.
• D. Increase heat load.

Answer: (B)

Cross-ventilation fins or jaalis are air-permeable screens placed at openings that let breeze pass through while controlling sunlight. Their openings are sized and patterned to promote cross-ventilation, so indoor spaces are cooled by fresh outdoor air instead of relying on artificial cooling. At the same time, the solid elements and the screen pattern block direct sightlines and reduce glare, providing privacy and a sense of security. The result is a cooler, more comfortable interior that still feels private and protected, with shading that cuts down heat from the sun.