Transparent facades, open atriums and light-filled escape routes are part of today's architectural standard. What the design gains in openness, however, the building authority assesses as a potential fire load and hazard zone. Fire protection in Germany is therefore not an optional extra but is bindingly regulated by the state building codes (Landesbauordnungen, LBO) of the 16 federal states.
The reason for the complexity is federalism: fire behaves the same way physically everywhere, yet the legal requirements for components such as fire-rated glazing often differ in detail between North Rhine-Westphalia, Bavaria or Berlin. Planners, architects and investors who are unaware of these differences risk costly redesigns, delays during approval – or, in the worst case, liability in the event of damage.
The Legal Framework: From the Model Building Code to the State Building Code
The Model Building Code (Musterbauordnung, MBO) only provides the framework. Issued by the Conference of Building Ministers, it has no legal force of its own but serves the 16 states as a template for their respective state building code.
Why differences exist at all
Every federal state may adapt the MBO to its regional needs. The BauO NRW, for instance, often sets stricter fire-protection requirements for densely built-up urban areas, while the BayBO (Bavarian Building Code) has recently simplified timber construction in particular and thereby deviated from the MBO.
For planning this means: the decisive code is always the LBO of the state in which construction takes place. Added to this are the relevant special-building ordinances – for example for assembly venues, hospitals or retail premises – which in many cases further tighten or specify the LBO requirements.
Building Classes 1 to 5 – the Starting Point of Planning
- GK 1 & 2: Detached residential buildings or small units up to 7 m in height; interior fire-protection requirements remain moderate. Fire-rated glass usually only comes into play at property boundaries or in special boiler rooms.
- GK 3: Buildings up to 7 m in height with more than two usage units. The LBO frequently requires fire-retardant components (30 minutes). Transparent partitions in corridors must then already comply with the fire-protection standard – for example with ARDOREX® Arnold Fire in class EI 30, which as laminated glass achieves up to 86 % light transmission (Source: ARDOREX® data sheet, as of 11/2024).
- GK 4: Buildings up to 13 m in height with usage units up to 400 m². The requirement rises to highly fire-retardant (60 minutes). At this critical threshold, the choice between E 60 (pure integrity) and EI 60 (with insulation) often has to be made. ARDOREX® Arnold Fire EI 60.18, with a Ug value of 4.6 W/(m²K) in laminated glass, has proven itself here.
- GK 5 & special buildings: Buildings over 13 m in height or those of special type and use; here, fire-resistant (90 minutes) generally applies. In the stairwells of these classes, transparent planning is barely feasible without high-performance fire-rated glass (EI 90). ARDOREX® Arnold Fire EI 90.24 reaches this class at up to 84 % light transmission.
What the LBO Protects: Three Central Objectives
- Preventing the outbreak of fire: Glass plays a minor role here because it is classified as a non-combustible building material (A1/A2 according to DIN 4102).
- Limiting the spread of fire: This is where fire-rated glazing comes into play. It is intended to prevent fire from crossing from one fire compartment into the next (fire walls, partition walls).
- Rescuing people and animals: the most critical objective. Escape routes – necessary corridors and stairwells – must remain free of smoke for a defined period and provide protection from radiant heat. This is exactly where ARDOREX® excels: the hydrogel layer keeps the temperature on the cold side, on average, to less than a 140 K increase above the initial temperature.
E, EW and EI: the European Classification in Detail
To implement the LBO requirements correctly, planners must have a firm command of the classification according to DIN EN 13501-2.
E (Integrity) – room closure
Historically referred to as G-glass. Such glazing only holds back flames and smoke; the dangerous heat radiation passes through almost unhindered. According to the LBO, it is only permitted where there are no combustible materials nearby and no one is directly endangered – for example in skylights or partitions without escape-route relevance.
EW (Radiation) – radiation limitation
An intermediate step that is rarely explicitly required in the German LBOs but is often used as compensation. EW glass keeps radiant heat below 15 kW/m² at a distance of one metre.
EI (Insulation) – thermal insulation
Referred to nationally as F-glass and the highest fire-protection standard. EI glass provides comprehensive protection against flames, smoke and heat; on the side facing away from the fire, the pane may heat up by an average of no more than 140 K above the initial temperature. ARDOREX® Arnold Fire covers classes EI 30 to EI 120 (Source: ARDOREX® data sheet, as of 11/2024). According to the LBO, EI is mandatory for all glazing in necessary corridors and stairwells – to safeguard evacuation.
