REI30 vs EI30 Explained
What Is the Difference Between REI30 and EI30?
The difference is the letter R.
Under the European fire-resistance classification system:
R = Loadbearing capacity
E = Integrity
I = Insulation
The number indicates the stated fire-resistance period in minutes.
Therefore:
EI30 relates to 30 minutes of integrity and insulation.
REI30 relates to 30 minutes of loadbearing capacity, integrity and insulation.
Approved Document B defines these three criteria in exactly this way.
Why Does This Matter for Window Contractors?
Because window and door schedules often contain terminology copied from:
- Fire strategies
- Architect drawings
- Structural drawings
- Door schedules
- Wall specifications
and the terminology isn’t always used consistently.
If the specification says:
REI30
you should not simply change it to:
EI30
because the product you want to use is EI30.
First determine what element is actually being classified.
R – Loadbearing Capacity
R relates to the ability of a loadbearing element to maintain its structural function during the stated fire exposure.
This is commonly relevant to structural elements such as:
- Loadbearing walls
- Floors
- Structural frames
A conventional non-loadbearing window or doorset may not itself have an R requirement in the same way a loadbearing wall does.
This is why blindly requesting an “REI30 window” can sometimes indicate that the terminology needs clarifying with the fire designer.
E – Integrity
E relates to resistance to fire in terms of integrity.
In practical terms, the element needs to continue acting as a barrier against the relevant passage of fire/flames and hot gases for the required period.
Examples:
E30
E60
indicate an integrity requirement without an I classification in the designation.
I – Insulation
I relates to resistance to fire in terms of insulation.
It concerns limiting temperature rise on the unexposed face during the fire-resistance period.
This is why EI glass is typically a more demanding requirement than integrity-only glazing.
What Does EI30 Mean?
E = Integrity
I = Insulation
30 = 30 minutes
So EI30 means the classified element achieves both integrity and insulation criteria for 30 minutes within the scope of its classification.
What Does EI60 Mean?
The same principle:
E = Integrity
I = Insulation
60 = 60 minutes
The classification period is doubled, but that does not mean you can create EI60 simply by making an EI30 pane thicker.
The complete assembly must have appropriate evidence.
What Does REI30 Mean?
R = Loadbearing capacity
E = Integrity
I = Insulation
30 = 30 minutes
This classification is particularly relevant to construction elements where structural loadbearing performance is part of the required fire resistance.
Approved Document B uses REI classifications for various fire-resisting structural constructions.
Can a Window Be REI30?
This question needs care.
A conventional window is usually not a loadbearing structural element.
Therefore, if an architect’s window schedule states:
REI30 window
do not assume you need a special window carrying an R classification.
Ask:
“Is REI30 the classification of the surrounding wall/element, with the glazed opening itself required to achieve EI30 or another classification?”
The fire consultant or architect should confirm the requirement.
Do not make that decision yourself.
Example – Fire-Rated Wall With Window
A partition is specified as:
REI60
The wall has a glazed opening.
That does not automatically mean the glazed window itself is described as REI60.
The required glazing classification needs to be determined from the fire strategy and applicable system design.
This is precisely why fire-rated enquiries need the complete specification rather than one copied code.
What Is E30?
E30 means 30 minutes of integrity.
It does not contain the I insulation criterion.
Do not substitute E30 glazing where the specification requires EI30.
What About EW30?
You may also encounter:
EW30
The W criterion relates to limiting radiant heat.
This is different again from EI performance.
If a specification asks for EW glazing, obtain a system classified for that requirement.
Do not convert EW to EI or E based on assumption.
FD30 vs EI30
Another common source of confusion.
FD30 is terminology traditionally used in the UK for a fire door providing 30 minutes’ fire resistance under the relevant national test/classification route.
EI30 is European classification terminology.
Do not casually describe them as identical.
The applicable test/classification route, smoke requirement, doorset design and project specification need to be considered.
FD30S
The additional S commonly indicates a smoke-control requirement.
Fire resistance and smoke leakage are separate performance considerations.
Approved Document B includes separate smoke-leakage provisions for relevant fire doorsets.
Why Fire Glass Is Not Enough
Suppose the specification asks for:
EI30
A glass supplier offers an EI30 glass product.
That does not automatically mean your completed window is EI30.
The classification relates to the assembled construction, potentially including:
- Glass
- Frame
- Beads
- Gaskets
- Intumescent materials
- Fixings
- Dimensions
- Supporting wall
Always buy the system, not just the rating printed on the glass datasheet.
Product Scope Matters
A tested/classified product may have limitations including:
- Maximum dimensions
- Minimum dimensions
- Aspect ratios
- Glass types
- Mullion arrangements
- Opening/fixed condition
- Supporting construction
Don’t extrapolate outside the evidence without a suitable assessment route.
The 30-Minute Myth
Contractors often think:
“It just needs to last 30 minutes.”
But different 30-minute classifications measure different criteria.
For example:
E30
is not the same classification as:
EI30
and neither should automatically be treated as:
REI30.
The letters matter just as much as the number.
Common REI/EI Mistakes
Mistake 1 – Ignoring the R
R has a specific meaning.
Mistake 2 – Treating E30 as EI30
Insulation is missing.
Mistake 3 – Assuming every fire-rated window is EI30
Different projects require different classifications.
Mistake 4 – Asking for “30-minute glass”
Too vague.
Mistake 5 – Copying the wall classification onto the window
The glazed opening may have a different required classification.
Mistake 6 – Assuming the glass rating proves the window rating
It doesn’t.
Mistake 7 – Changing system dimensions
Evidence has scope limits.
Real-World Example
An architect’s schedule states:
External glazed screen – REI30
The window supplier produces an aluminium EI30 system.
Is that acceptable?
You cannot answer that from those two phrases alone.
The correct action is to ask the architect/fire consultant:
- Is the glazed screen itself required to be loadbearing?
- Is REI30 describing the surrounding wall construction?
- What classification must the glazed assembly achieve?
- Is insulation required?
- From which direction must it be tested/classified?
- What supporting construction applies?
Only then should the product be selected.
What Should a Contractor Ask?
Instead of:
“Can you quote a 30-minute fire window?”
Ask:
“Please confirm the required fire-resistance classification for the glazed assembly: E30, EI30, EI60, EW30 or other, together with the supporting construction and required direction of fire exposure.”
That one question can prevent major problems.
Frequently Asked Questions
What does R mean?
Loadbearing capacity.
What does E mean?
Integrity.
What does I mean?
Insulation.
What does EI30 mean?
30 minutes’ integrity and insulation within the classified scope.
What does REI30 mean?
30 minutes’ loadbearing capacity, integrity and insulation.
Is REI30 better than EI30?
“Better” is the wrong way to look at it. They describe different performance criteria.
Does a normal window need R?
A conventional non-loadbearing window may not require loadbearing classification; confirm the required performance with the fire designer.
Is E30 the same as EI30?
No.
Is FD30 the same as EI30?
Do not treat them as automatically interchangeable; they come from different terminology/classification routes.
Does EI30 glass create an EI30 window?
No. The complete assembly needs appropriate evidence.
Related Guides
- Part B Explained
- Fire-Rated Windows Explained
- Fire-Rated Doors
- Laminated Glass Guide
- Building Control Checklist
- Common Building Regulation Failures
Trade Tech Technical Support
For every fire-rated enquiry, obtain the actual fire classification before requesting manufacture.
The enquiry should state:
- E / EI / EW / REI classification
- Minutes
- Sizes
- Fixed or opening
- Supporting wall type
- Fire exposure direction
- Other requirements such as U-value, acoustics or safety glazing
If the architect’s schedule uses unclear or conflicting terminology, get it clarified before ordering.
Important: Do not substitute one fire classification for another because it appears similar. Fire-performance design should follow the project’s fire strategy and suitable classification/test/assessment evidence.