When you are selecting fire safety glass for any build (residential or commercial) it’s always worth taking the time to understand the different performance classifications available. We find that the underlying terminology can look quite technical at first glance, but those letter codes represent vital, not minor, differences in how the glass actually performs during a fire. The most common fire ratings that you will come across are E and EI.
E vs. EI: The Critical Distinction
While they sound similar, E vs EI fire rated glass offers vastly different levels of protection. Simply knowing that ‘E’ means integrity and ‘EI’ means insulation, for example, completely changes where you can specify that product within a building’s design.
This isn’t just about meeting minimum compliance requirements; the type of safety glass you choose directly determines the level of protection afforded to occupants during an evacuation. Effectively, choosing the right glass is crucial for creating safe escape routes and protecting the overall structure.
This guide breaks down the key distinctions between E and EI fire rated glass to help you specify the correct solution for your project.
Understanding Fire Resistance Classifications
Fire resistant glass is classified according to European standards, primarily BS EN 13501-2 (based on tests like the BS EN 1363 series). These classifications determine how a glass system (including the frame and glazing) performs when exposed to fire. The rating is usually followed by a number which indicates the duration, in minutes, that the glass can withstand the test conditions. You will typically see 30, 60, 90 or 120 minutes.
The main performance criteria that are measured are:
- Integrity (E),
- Radiation Control (W)
- Insulation (I)
Let’s take a look at what these actually mean in practice.
What is E Rated Fire Glass? (Integrity)
E rated glass provides the most basic level of fire protection. The ‘E’ stands for ‘Integrity’. Integrity is how well the glass blocks flames and hot gases from passing through to the non-fire side.
E Rated glass is designed to remain physically stable and prevent the spread of fire for its rated time period, such as 30 or 60 minutes. However, E rated glass does not stop the transfer of heat. E Rated glass in a fire can become incredibly and dangerously hot, allowing radiant heat to pass through it. This heat can be strong enough to ignite combustible materials and can make escape routes difficult or impossible for people to use.
What is EI Rated Fire Glass? (Integrity and Insulation)
EI rated glass offers a much higher and safer level of protection. The ‘EI’ rating means the glass provides both ‘Integrity’ (E) and ‘Insulation’ (I).
Like the E classification, EI rated glass prevents flames and smoke from getting through. But crucially, it also provides a barrier to heat. The ‘Insulation’ property of EI rated fire glass ensures that the surface temperature on the non-fire side of the glass remains below a certain threshold for its rated duration.
EI rated glass prevents flames and smoke from getting through with intumescent interlayers within the glass. When these layers are exposed to heat, they turn into a rigid, opaque shield that blocks the dangerous transfer of radiant heat, keeping the protected side cooler. EI rated fire glass ensures that evacuation routes remain safe for people to use and prevent spontaneous ignition of nearby objects.
Key Differences: E vs EI Fire Rated Glass
The fundamental difference in E vs EI fire rated glass comes down to heat transmission. An E rated glass partition might stop flames, but the intense heat it radiates can still cause severe burns or prevent people from using an escape corridor.
EI rated glass, on the other hand, provides a complete fire barrier. It contains the fire and the heat, which gives people valuable time to evacuate safely and it also offers a greater protection for firefighters. This distinct difference between E rated and EI rated glass is key when designing spaces where people inside the building might be in close proximity to the glazed area during an evacuation.
Why Insulation Matters: The Hidden Dangers of Radiant Heat
The risk of radiant heat is often underestimated. Radiant heat can travel through the air and be strong enough to ignite furniture, carpets and other flammable materials on the opposite side of a fire barrier, even without any direct contact with flames.
This can cause a fire to spread rapidly through a building, jumping across corridors and compartments that were designed to contain it. More importantly, it can make escape routes incredibly dangerous. A corridor lined with only E rated glass could feel like an oven, making it impossible for people to pass safely.
To explain the difference between E and EI rated glass further, we are going to provide a specific example using a hospital building. In a hospital, evacuation can take longer because the people inside might be vulnerable or slow-moving. If a fire breaks out near a corridor that uses E rated glass, the heat radiating through that corridor could make that corridor impassable, long before the flames break through. If this same corridor used EI rated glass like our fire rated glass partitions, you ensure that corridor remains usable as an escape route and this is a protected area that can stay safe from the secondary effects of a fire.
The performance of EI rated glass is essential for applications like stairwells, protected corridors and lobbies.
Applications for Different Types of Fire Safety Glass: E vs EI?
As we have illustrated in the example above, the choice between E and EI glass depends entirely on the building, where the glass is being applied and by the requirements that are set out in UK Building Regulations.
E rated glass is generally restricted to locations where the risk of radiant heat is not a primary concern. This can sometimes be the case in external windows where evacuation is not an issue.
EI rated glass is the required specification for most internal applications that form part of a building’s fire strategy. This includes:
- Protected Escape Routes: Stairwells, corridors and lobbies that are designated as escape routes must be protected from heat.
- Partitions and Screens: Glazed systems separating different fire compartments.
- Doors: Fire rated aluminium doors that separate corridors or rooms.
Here at Aluminium Fire Systems we provide a range of EI certified fire systems, including EI 30, EI 60, EI 90 and EI 120 fire rated products, ensuring a solution is available for any integrity and insulation requirement.
Why Choose Aluminium Fire Systems
At Aluminium Fire Systems (AFS), we are dedicated to providing fully compliant and effective fire safety solutions because we understand that our products play a critical role in protecting lives and buildings.
Our team focuses on delivering quality work, from initial consultation to final delivery. If you buy from us, you are buying directly from the manufacturer. The benefits of this are we offer competitive pricing without ever compromising on the quality or compliance of our systems. All of our fire rated products are manufactured here in the UK and we ensure that they meet the highest standards.
We pride ourselves on managing our projects effectively with fast lead times and on-time nationwide delivery to help you to keep your project on schedule. As well as that, with every project, we send you a full compliance pack, to give you complete peace of mind that you have installed a certified and tested fire protection system.
Contact Us
If you need any help with fire rated solutions then you can contact us today by phone on 0121 277 4870 or send us a message via the form on our contact page. Or you can find more information on our website by visiting our fire rated products page or fire rated FAQs page.
Types of Fire Safety Glass: E vs EI: Frequently Asked Questions
What are the building regulations for fire rated glass UK?
When dealing with fire-rated glass regulations in the UK under Fire Safety: Approved Document B, it is crucial to look beyond the basic paperwork. While a standard ‘E’ rating is designed to hold back flames for thirty minutes, it does not necessarily block dangerous radiant heat, which is why an ‘EI’ insulation rating is often the safer choice for busy escape routes.
Another important thing to note is that fire rated glass is only as effective as its surroundings meaning you must ensure that it is fitting within a fully compatible system of frames and seals that have been tested to BS EN 1634 (for doors) or tested to BS EN 1364 (for partitions) and not just treated as a standalone product.
To be certain everything is compliant, we would recommend checking for the permanent stamp on the pane of glass, as this identifies the manufacturer and confirms the specific rating the fire system has achieved.
What does EW rated glass mean?
EW rated glass is a classification that sits between E and EI. It offers ‘Integrity’ and a degree of ‘Radiation’ control (W), but not to the same level as the ‘Insulation’ provided by EI glass. It reduces the amount of radiant heat that passes through but does not block it completely. For most applications where heat transfer is a concern, EI rated glass remains the preferred and often required fire rated solution.
Can I use E rated glass in any application?
It depends. The use of E rated glass is permitted but is restricted by UK Building Regulations. It is often not suitable for protected escape routes (like stairwells) where the transfer of radiant heat could hinder evacuation. Always consult with a fire safety expert or your local building control body.
How long do fire glass ratings last?
The rating refers to the duration the glass and its frame can withstand fire under test conditions. For example, an EI 60 system provides 60 minutes of integrity and insulation. We offer a range of fire rated products including 30 minute fire rated windows and systems that can provide up to 120 minutes of protection.
What is the BS EN 1363 series?
Think of BS EN 1363 as the European rulebook for fire testing. It sets the specific methods laboratories must use to measure exactly how long a building component, such as a wall or a fire door, can withstand a fire before it fails.
The standard is split into two main parts to cover different scenarios:
- BS EN 1363-1: This covers the standard test. It is the routine procedure used for the vast majority of construction materials.
BS EN 1363-2: This is for special cases. It provides alternative testing methods for environments where a fire might burn hotter or behave differently than usual (such as in a tunnel or a chemical plant).
About The Author
This article has been written by Lauren Walker who is the Managing Director of Aluminium Fire Systems. Lauren has a wealth of experience in fire rated glass products. Lauren is passionate about ensuring that all of her clients receive fully compliant fire rated solutions that enhance safety.