Technical guide
Fire rated glass ratings explained
Fire glazing is classified under BS EN 13501-2. E means integrity — it holds back flame and hot gases. EW adds a limit on radiated heat. EI adds insulation, keeping the unexposed face cool. The number is the tested minutes.
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E — integrity only
Holds back flame and smoke for the stated period. The glass gets extremely hot, so anyone close to it is still at risk from radiated heat. Used where separation distance is generous.
EW — integrity plus limited radiation
Caps the radiated heat at 15 kW/m² measured one metre away. Often the sensible middle ground on atrium and internal separation where full insulation is not justified.
EI — integrity plus insulation
The unexposed surface stays cool enough to touch. This is what protected escape corridors and stairwells normally require, and it costs materially more because of the intumescent layers involved.
The rating is the whole assembly
Test evidence covers the exact combination of glass, frame, beads, gaskets, fixings and maximum pane size. Change any element and the rating no longer applies — an EI60 pane in an untested frame has no rating at all.
Marking and evidence
Every compliant pane is permanently marked with its classification. If a pane carries no mark, treat its rating as unproven until documentation is produced.
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