Rear-ventilated façades and fire classification for high-rise cladding

Ashwanii Khanna explained the principles of rear-ventilated cladding systems and the practical meaning of fire classifications A2 and B for high-rise applications, drawing on material performance data and completed Indian projects.

A rear-ventilated façade creates a continuous cavity between the wall and the outer cladding so that air can enter at the base, rise and exit at the top. In Ahmedabad’s hot climate this natural stack effect carries heat away from the building, reducing the load on HVAC systems while also providing acoustic benefits and a degree of thermal insulation.

Fire classes and real-world behaviour

FunderMax offers an A2-class product (Mlook) that does not reach ignition temperature and a Class B product that accounts for the large majority of sales. Class B material crosses the ignition point but does not reach flashover. Supporting data included ASTM E84 Class A results, EN classifications of B-s1,d0 or B-s2,d0 depending on thickness, and A2-s1,d0 for the non-combustible grade.

Managing cavity fire spread

Because a rear-ventilated system deliberately leaves an air gap, fire can potentially travel vertically. Expanding fire stops that activate under heat create compartmentation and confine any fire to a single floor.

Project applications and double-skin options

Completed high-rise installations include Cloud Nine in Ahmedabad, HM Grandeur in Bangalore (G+20), ONGC in Mumbai, Jain Heights in Bangalore (G+23) and TRIL-Taj in Chennai.

HM Grandeur Bangalore — **HM Grandeur, Bangalore.** G+20 tower with riveted 6 mm Max Exterior panels on an aluminium framework.

Double-skin configurations deliver both thermal and visual comfort. The outer layer can be detailed as louvres whose angle is determined by sun-path analysis.

Ahmedabad University louvres — **Ahmedabad University.** Max Exterior panels detailed as vertical and horizontal shading elements that respond to sun-path analysis.

**Lucknow marketing office.** Double-skin outer layer that cuts excess heat and glare while improving the shading coefficient.

NET College Raichur — **NET College, Raichur.** Passive sun-shading system designed from full sun-path analysis, reducing heat transfer to the inner layer.

Khanna concluded that awareness, proper design, insulation choices and detailing remain the practical levers for improving façade fire safety on tall buildings.