Fire Resistance Classes E, EW, and EI – Simply Explained, Technically Correct

Why These Three Letters Determine Safety

In the event of a fire, every minute counts. Flames, smoke and heat must be stopped before they can spread. To ensure this, building components are tested according to fixed rules – including the European standard EN 13501-2.

The so-called fire resistance classes E, EW and EI indicate how long a component – such as a wall, door or glazing – retains its function in a fire. They are the language system of fire protection. Those who understand them can plan buildings safely and prepare approvals with confidence.

What do E, EW and EI mean?

The abbreviations may seem abstract, but they are easy to understand:

E = Integrity
The component remains tight. It prevents flames or hot gases from penetrating through.

W = Radiation Control
It limits thermal radiation that could otherwise endanger people or materials on the unexposed side.

I = Insulation
This measures whether certain temperature limits on the unexposed (cold) side are not exceeded. When letters are combined, they indicate the tested classification:

E 30, EW 60 or EI 90 – the number indicates the minutes of fire resistance.

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How are fire resistance classes tested?

During a fire test, a wall, door or glazing is exposed to fire on one side according to the standard temperature-time curve (ETK).

The temperature in the test furnace rises to over 800 °C within minutes.

The criteria are clearly defined:

• E: no flames, no smoke, no openings

• W: thermal radiation ≤ 15 kW/m²

• I: temperature rise ≤ 140 °C on average or ≤ 180 °C at any single point

If the component meets these conditions for 30, 60 or 90 minutes, it receives the corresponding classification. A glazing with EI 90 therefore remains functional for at least 90 minutes – even on the unexposed side.

How long does EI 60 really last?

EI 60 means that the component withstands fire and heat for at least 60 minutes without the temperature on the unexposed side rising to a dangerous level. In real fire tests, certified systems often achieve 70 to 75 minutes – a safety margin that may be considered in planning.

Why This Classification Is So Important

Fire resistance classes are not a formality. They determine how much time people have to exit a building and whether fire spread can be prevented. Especially in modern buildings with extensive glazing or open floor plans, they are indispensable.

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When is EW 30 sufficient?

According to European standards, EW 30 is sufficient in certain areas. This class reduces radiant heat so escape routes remain safe. In Germany, however, the EW class is hardly ever required by building authorities and is not regulated. It is mentioned here solely for completeness.

Standards and Legal Framework

EN 13501-2 defines how building components are classified across Europe. In Germany, the Model Building Code (MBO) adopts this classification and distinguishes between fire-retardant, highly fire-retardant and fire-resistant components – depending on the required time rating.

The specific requirements, however, result from the respective state building regulations and may vary regionally. This is why the correct class is always part of the construction type approval and must be specified precisely in planning.

Typical guideline values (varying by federal state):

• Stairwells and escape routes: at least EI 30

• Fire compartments between different occupancy units: usually EI 90 – EI 120

Differences at a glance

Put simply: E stops fire, EW keeps distance, EI stays cool.

How planners choose the correct class

The decision depends on usage, number of occupants and neighbouring areas:

• E components: technical rooms, storage rooms, partitions without occupied spaces behind them

• EW components: only in countries where this class is officially used

• EI components: archives, laboratories, escape routes – anywhere temperature transmission would be critical

The denser the use and the more valuable the contents, the higher the class that should be selected.

Attention: The planning and implementation of fire-resistant glazing in Germany are regulated at state level and may differ significantly from one federal state to another.

Practical example: Glazing in a fire compartment

A floor-to-ceiling glazing separates the corridor from an office.

Here, a system of class EI 60 offers reliable protection: the glass panes remain tight for 60 minutes, the hydrogel interlayer evaporates and forms an insulating barrier. On the unexposed side, temperatures remain below 140 °C – people can pass safely, materials do not ignite.

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Why hydrogel is so effective in a fire

Hydrogel systems evaporate when exposed to heat.
The resulting water vapour reduces temperature; the layer becomes opaque and insulates. This maintains integrity without causing the fire-side glass to shatter. This product characteristic has proven itself in modern EI systems – safe, transparent and maintenance-free.

Modern fire protection systems are true multi-talents:

• Thermal insulation: Ug values down to 0.5 W/(m²K) reduce heating costs.

• Sound insulation: tested up to 46 dB Rw – ideal for offices or clinics.

• Light transmission: up to 86% – bright spaces despite safety requirements.

• UV resistance: no clouding of the fire-resistant glazing.

• UV permeability: beneficial for plant growth and well-being.

These values are achieved by tested glass constructions according to EN 673, EN 410 and EN ISO 717-1. They show that fire protection does not need to be heavy or dark.

Sustainability and the Future

Fire-resistant glass is increasingly becoming a sustainable building component. New hydrogel systems are recyclable, and wood or metal frames can be reused. Added to this are long life cycles and combined functionalities: one piece of glass protects not only against fire, but also against noise and energy loss. This results in true multi-purpose performance – a decisive argument in modern architecture.

Understanding Safety, Planning Correctly

Fire resistance classes E, EW and EI are more than letters. They describe how long a component protects lives. Those who use them correctly not only meet standards, but also create trust – among users, authorities and investors. Further technical information on certified glass systems of classes EI 30 to EI 120 can be found at ISOLAR ARDOREX® fire-resistant glass www.isolar.de