Glass Curtain Wall Fire Risk: NFPA 285 and Grenfell Lessons

Glass-clad high-rises are the signature of modern architecture. But aluminum composite panels (ACM) behind the glass can spread fire rapidly up the facade. The 2017 Grenfell (London) and 2009 Mumbai Taj fires are two extreme examples. NFPA 285 defines a full-scale fire test for facade composite systems. This article covers the test procedure, material risks and the regulatory situation in Turkey.

Curtain Wall Anatomy

A typical curtain wall system:

• Outer skin: Tempered glass or ACM (aluminum composite material)
• Air cavity: 25-100 mm (capillary drainage)
• Insulation: PIR, PUR, MW (mineral wool) or EPS
• Inner wall: Concrete or light steel framing

Critical question: will these layers carry a fire from floor to floor, or can they contain it at one floor?

NFPA 285 Test Procedure

Full-scale fire test conducted on a two-story mock-up:

• Lower level burn room — 35 MW fire simulation
• Upper level has window opening — flames exit here
• 30-minute test duration
• Pass criteria: flames do not spread >4 m above the lower window; interior surface temperature stays below 500 °C; facade does not detach

ACM Risk Assessment

Two core types in aluminum composite panels:

• PE (polyethylene) core: Cheap, combustible, rapidly spreading. Used at Grenfell. Fails NFPA 285.
• FR (fire-retardant) or MW core: non-combustible or very slow-spreading. Passes NFPA 285.

Cost difference is 15-30% per m2 — critical for fire safety.

Post-Grenfell Changes

The June 2017 Grenfell Tower fire (72 dead) triggered bans on PE-core ACM across the US, UK and EU:

• UK: combustible cladding banned on 18m+ buildings from 2018
• EU: CPR A2/B-s1,d0 minimum
• USA: IBC 2021 mandates NFPA 285; many states add restrictions
• Australia: ACM removal programs initiated

Turkey Status

Turkey's BYKHY regulation Article 27 addresses facade fire safety directly: external facades of buildings with a building height above 28.50 m must be of limited-combustibility material (zor yanıcı, A2-s1,d0 under Annex 2/Ç), and at least "zor alevlenici" in other buildings; between unprotected openings of two floors there must be a fire-resistant solid band at least 100 cm high, or sprinklers at no more than 2 m spacing within 1.5 m of the inside of the facade (Article 27(1)). In curtain walls with open or ventilated joints, facade and insulation materials must be at least limited-combustibility (Article 27(3)(b)). There is no NFPA 285-style full-scale test mandate; material reaction-to-fire classes are given in Annex 2/Ç to TS EN 13501-1 and TS EN 13501-5 (Article 29(6)(ç)). TS EN 13501-1 Class A1/A2 certification is the practical baseline. Bare PE ACM is still seen on projects; insurers flag such buildings as 'high risk' with elevated premiums.

For the Mechanical Engineer

1. Request insulation certification (at least limited-combustibility, i.e. A2-s1, d0, for buildings above 28.50 m and for curtain walls with open or ventilated joints; at least "zor alevlenici", e.g. B-s1, d0, in other buildings) when facade documents arrive
2. Watch sprinkler proximity to outer facade — no protrusion through windows
3. Smoke exhaust must work during facade fires (positive pressure)
4. Firestops between floors inside the facade are architect's responsibility — verify anyway

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