Fire rated glazing is glass and framing tested together as a system to resist fire for a set time. E-rated glazing holds back flames and hot gases (integrity), EW adds a limit on the heat radiated through it, and EI also keeps the protected side cool enough to pass close by (insulation); the number, such as EI30 or EI60, is the time in minutes. Fire-rated glazing is a standard requirement on most commercial, mixed-use and higher-risk residential buildings in the UK. The Building Safety Act 2022 and the wider reforms that followed the Grenfell Tower fire have raised the bar on how fire-safety-critical elements are specified, evidenced and recorded. This guide gives architects and project managers a practical overview of the technical and specification issues behind fire-rated windows, doors, screens and curtain walling.
Fire rated glazing classifications: E, EW and EI
Fire-resisting glazed elements are classified by how long they keep each performance criterion in a fire resistance test, in minutes. E is integrity: the element stops flames and hot gases passing through. W is radiation: it limits the heat radiated from the unexposed face. I is insulation: it limits the temperature rise on the unexposed face. Classifications are given to BS EN 13501-2. Common ones on project specifications:
- E30 / E60 — integrity only; used only where the fire strategy does not call for control of radiation or heat transfer
- EW30 / EW60 — integrity plus limited radiation; used where the fire strategy accepts some heat transfer but needs radiation limited
- EI30 / EI60 — integrity and insulation; generally needed where glazing forms part of a fire-resisting wall such as a compartment wall — Approved Document B limits where uninsulated glazing can be used
- EI90 / EI120 — longer periods, used where the fire strategy calls for higher fire resistance, for example in taller buildings
| Class | Stops flames and hot gases | Limits heat radiated through the glass | Keeps the protected face cool | Glass typically used |
|---|---|---|---|---|
| E (integrity) | Yes | No | No | Non-insulating fire-resistant glass: special toughened, ceramic or wired |
| EW (integrity and radiation) | Yes | Yes, below 15 kW/m² measured 1 m from the glass | No | Fire-resistant glass products tested to meet the radiation limit |
| EI (integrity and insulation) | Yes | Yes | Yes, average temperature rise no more than 140 °C | Insulating fire-resistant glass with intumescent interlayers or gel |
What is EW fire rated glass?
EW glass keeps its integrity and limits the heat radiated through it: in the test, radiation measured 1 m from the unexposed face must stay below 15 kW/m² for the classified period. It does not limit the temperature of the glass itself, which can become too hot to stand next to, so EW is used where the fire strategy accepts some heat on the protected side but not the full radiation of an integrity-only pane. EI glazing goes further: the average temperature rise on the unexposed face must stay at or below 140 °C, with no single point rising more than 180 °C, which is why it is used where people need to pass close to the glass on an escape route.
Older ratings: FD30, 60/60/60 and 45 minutes
Older UK specifications written to BS 476 give fire resistance as up to three numbers in minutes — loadbearing capacity, integrity and insulation — such as 60/60/60, or -/30/30 for a non-loadbearing glazed screen, and describe doors as FD30 or FD60. The nearest European classification for a non-loadbearing glazed element is E, EW or EI followed by the same period, but the two test regimes are not identical, so the fire engineer or building control should confirm which is accepted for each element. Ratings of 45 minutes are more common in North American codes; UK fire strategies most often call for 30 or 60 minutes, with longer periods where needed.
Types of fire rated glass
Fire rated glass falls into two broad groups, and the group decides which classification the glazing can reach:
- Non-insulating fire-resistant glass, such as specially toughened (not ordinary toughened safety glass), ceramic or wired glass, which holds back flames and smoke and is used for E and, depending on the product, EW ratings
- Insulating fire-resistant glass, made with intumescent interlayers or a gel between the panes, which turns opaque and insulating in a fire and is used for EI ratings
- Fire-resistant insulating glass units, sometimes called fire rated double glazed units, which combine a fire-resistant pane with a thermally insulating unit for external walls, fire rated windows and façades
The glass only achieves its rating in the frame, seals and fixings it was tested with, which is why fire rated glazing is always specified as a system. Steel or aluminium frames with intumescent seals are usual on commercial projects, and products for external use must be rated for exposure to sunlight and weather.
Fire resistance test standards for fire rated glazing
- BS EN 1364-1 — fire resistance tests for non-loadbearing walls, including glazed screens and partitions
- BS EN 1364-3 / BS EN 1364-4 — fire resistance tests for curtain walling (full and part configuration)
- BS EN 1634-1 — fire resistance tests for door and shutter assemblies and openable windows
- BS EN 16034 — product standard for pedestrian doorsets and openable windows with fire resistance and/or smoke control characteristics, used alongside BS EN 14351-1
- BS EN 13501-2 — the classification standard that turns test results into E, EW and EI ratings
Always ask for the test evidence (or a third-party assessment based on it), not just a system brochure. The evidence should cover the configuration you are installing — frame type and size, glass type and pane size, infill panels, fixings and seals. Deviations from the tested configuration can invalidate the classification.
The fire resistance tests above are for non-loadbearing elements. Loadbearing glazed elements, such as fire rated walk-on glass floors, are tested under the BS EN 1365 series and classified with R for loadbearing capacity, for example REI60.
Fire rated screens, doors, windows and curtain walling
Fire rated glazing is specified as one of four kinds of element, and each is tested in its own way. The fire strategy marks which openings need a rating and the classification for each; the element type then sets the test evidence to ask for.
| Element | Typical locations | Fire resistance test |
|---|---|---|
| Fire rated glazed screens and partitions | Stair and lift lobby screens, corridor partitions on protected escape routes, glazed office fronts on a compartment line | BS EN 1364-1 |
| Fire rated doors | Doors set into fire rated screens, stair and lobby doors, doors on escape routes | BS EN 1634-1 |
| Fire rated windows | Windows in a compartment wall, windows onto a protected stair, external windows where fire spread between buildings limits unprotected glazing | BS EN 1364-1 (fixed), BS EN 1634-1 (openable) |
| Fire rated curtain walling | Glazed façades on a compartment line or beside a protected stair or escape route | BS EN 1364-3 / BS EN 1364-4 |
Screens and doors are usually designed together, because a door in a glazed screen needs test evidence for the door, the screen and the way the two are combined. Our fire rated screens and partitions page covers glass partitions, FD30 and FD60 screens and cuttable fire glass in more detail.
Fire rated glazing and the Building Safety Act 2022
The Building Safety Act 2022 introduced a new regime for higher-risk buildings (HRBs). During design and construction, an HRB in England is a building at least 18 m tall or with at least seven storeys that contains at least two residential units; hospitals and care homes that meet the same height test are also included. Since October 2023, building control for HRBs sits with the Building Safety Regulator, with approval gateways before construction starts (Gateway 2) and before occupation (Gateway 3), and a "golden thread" of building information that must be kept up to date.
Third-party certification is not a blanket legal requirement for every product, but on HRBs in particular, clients, approvers and insurers expect clear, traceable evidence that each fire-safety-critical element performs as specified and was installed as tested. Product certification and third-party installer schemes are the most straightforward way to provide that evidence.
For residential buildings below 18 m, Regulation 7(2) does not apply, but Approved Document B still sets expectations for external walls, and lenders may ask for an EWS1 assessment on existing blocks of flats. Fire-rated glazing in aluminium or steel frames with tested seals is generally well placed, but the documentation matters as much as the product.
Fire rated glazing specification checklist
- Define the required classification (EI30, EI60 and so on) from the fire engineer's strategy — over-specifying adds cost without a safety benefit
- Confirm whether the element is loadbearing or non-loadbearing, as this changes the test standard
- Ask for test evidence or a third-party assessment that covers the exact configuration, and record it in the project information
- Coordinate fire-stopping and cavity barriers at junctions with the structural engineer and main contractor
- Where the client requires it, use an installer covered by a recognised third-party fire installation scheme, such as BM TRADA Q-Mark or FIRAS
Where a steel fire-rated façade is specified, we also work with Jansen VISS Fire. Our curtain walling specification guide covers fire-rated curtain walling alongside thermal performance and testing, our façades and cladding guide covers the external wall rules, and our commercial doors guide covers fire doors, escape hardware and access.
Frequently asked questions
What is fire rated glazing?
Fire rated glazing is glass and framing tested together to resist fire for a set time, classified as E (integrity), EW (integrity with limited radiation) or EI (integrity and insulation), followed by the time in minutes, such as EI30 or EI60.
What types of fire rated glass are there?
Non-insulating fire-resistant glass, such as specially toughened, ceramic or wired glass, is used for E and some EW ratings. Insulating fire-resistant glass, made with intumescent interlayers or a gel between the panes, is used for EI ratings. Both only achieve their rating in a tested frame and seal system.
What are the advantages of fire rated glazing?
It keeps a fire compartment or escape route intact while letting daylight through and keeping sightlines open, so corridors, stairs, lobbies and façades can be glazed instead of solid while still meeting the fire strategy.
What affects the cost of fire rated glazing?
Mainly the classification and period: insulating EI glass is thicker and heavier than E or EW glass, and 60 minutes costs more than 30. Pane size, frame material, door hardware, the evidence needed for the exact configuration and any third-party installation scheme the client requires also affect the price.
Can fire rated glazing be used externally?
Yes, in fire rated windows and curtain walling, but the glass must be a product rated for external use, because some insulating interlayers are sensitive to sunlight and temperature. The tested scope of the system should cover the external application.
What does EI60 or EI90 mean on fire-rated glazing?
EI60 means the glazed element kept its integrity (E) and insulation (I) for at least 60 minutes in a fire resistance test, classified to BS EN 13501-2; EI90 means the same for 90 minutes. It limits both the passage of flames and hot gases and the temperature rise on the protected side.
What is the difference between EW and EI fire-rated glass?
Both keep their integrity in a fire. EW glazing also limits the heat radiated from the unexposed face, to below 15 kW/m² measured 1 m away, while EI glazing limits the temperature rise on that face, which gives a higher level of protection to people on the other side.
Can fire rated glass be double glazed?
Yes. Fire-resistant insulating glass units combine a fire-resistant pane with a second pane in a sealed unit for thermal performance, and are used in external windows, doors and curtain walling. As with single panes, the unit is only rated in a frame system it was tested with.
What does 60/60/60 mean on a fire rating?
It is the older BS 476 way of writing fire resistance: loadbearing capacity, integrity and insulation, each in minutes. A non-loadbearing glazed screen is written with a dash for loadbearing capacity, such as -/30/30. The European equivalent uses classes such as EI30 or EI60, and the fire engineer or building control confirms which is accepted.
What is the difference between a fire rated screen and a fire rated window?
A fire rated screen or partition is a fixed run of glazing that forms part of an internal wall, often with a door set into it, tested to BS EN 1364-1. A fire rated window is an individual window set into a wall, often an external wall; fixed windows are tested to BS EN 1364-1 and openable ones to BS EN 1634-1.
What is a higher-risk building?
During design and construction, a higher-risk building in England is one at least 18 m tall or with at least seven storeys that contains at least two residential units. Hospitals and care homes that meet the same height test are also included.