Glass-facade high-rises (unitized curtain wall) carry vertical fire-spread risk (leapfrog effect) across slab edges (perimeter void). ASTM E2307 perimeter fire-barrier, ASTM E119 walls and ASTM E814 firestop penetration apply separately. After Grenfell 2017, facade-combustibility classifications were tightened.
Perimeter Void Risk
- Slab edge: 25-150 mm gap between slab and facade
- Spandrel panel: narrow band between windows - full-glass prohibited
- Mullion: vertical frame - 2h firestop
- Isolation: structural insulation + fire barrier
- Leapfrog fire: window blowout → upper floor entry
ASTM E2307 Test
- Test: two-floor mock-up
- Duration: 2 hours min (F and T rating)
- Fire scenario: interior room fire + windowout flame plume
- T rating: slab temperature below 140 C
- F rating: no flame passage
- Mineral wool: most common - 4 pcf density, 4 inch thick
Spandrel Panel
- Height: 900 mm min for plume limiting
- Back-up: cement board or metal
- Shadow box: view-blocked area behind glass
- Insulation: mineral wool; aluminum composite panel PROHIBITED
- Grenfell lesson: PE-core ACM panels must be A1/A2
Firestop Design
- Mineral wool: 20-35 percent compression
- Smoke seal: silicone sealant top
- Safing clip: Z-shape metal retention
- Movement: 25 mm building sway accommodated
- UL HW/CW system: listed detail
Worldwide Incidents
- Grenfell 2017: 72 dead, ACM cladding
- The Address Dubai 2015: facade leapfrog
- Mermerler Residence 2012: Istanbul facade fire
- Beckton London 2019: HPL cladding
- Regulation: Turkish BYKHY Annex 2/F, Class A2-s1,d0 above 28 m
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Sources & Further Reading
ASTM E2307, ASTM E119, ASTM E814, NFPA 5000, BYKHY Annex 2/F, EN 13501. NFPA 5000 Building Construction Code.