Fire protection of thermally insulated facades

When using a thermal insulation composite system, there is always the question of fire protection

All ETICS must be approved by the building authorities. Comprehensive fire safety tests are part of such approvals. Only systems that pass these tests are allowed to be marketed.

According to the European classification, the new Euroclass replaces the national classification. The classes defined in EN 13501-1 cannot be totally compared with the fire resistance classes according to DIN 4102-1. For ex. the European classes define other fire effects like smoke development – classified in three classes s1, s2 and s3 – and the burning dripping of building materials during a fire – classified in three classes d0, d1 and d2.

As a rule: the higher the number, the worse the fire resistance.

The decision in favour of a specific building material class and a corresponding system depends on type and use of the building, and the individual safety requirements.

Fire reaction class defines safety level

Concerning the facade, a distinction is made between two relevant building material classes: A1/A2 - "non-combustible" and B1 - "flame-retardant" while A1 scores with the highest fire safety level.

The building material classes do not only refer to the insulation material, but also to the tested and approved system. The choice of building material class depends on the use of the building, the individual safety requirements and the height of the building: the higher the building, the higher the fire protection requirements. For a building height ≥ 22 meters, systems of building material class A must generally be selected; details are defined by the regional building regulations.

Play it safe: all-mineral ETICS

ETICS based on mineral insulation materials fulfil the highest requirements. They contain non-combustible rock wool as insulation material; bonding mortar and reinforcing mortar as well as topcoat render also consist of non-combustible raw materials, such as quartz sand, hydrated lime and white cement. Fully mineral ETICS are therefore categorized in building material class A1. The high fire safety level of all-mineral systems facilitates their planning and processing.

The fire protection construction is extremely simple, as it does not require any elaborate detailing. In contrast to other insulation systems, all-mineral solutions do not require additional fire barriers. They can also be used in high-rise buildings up to 100 meters without any problems. They are particularly suitable for buildings where non-combustibility is required, such as hospitals and schools. Other health and care facilities are also increasingly relying on all-mineral systems, as residents are often restricted in their mobility and therefore, particularly at risk in the event of a fire. In addition, fully mineral ETICS installed on a mineral wall-building material (e.g. brick or pumice) achieve a homogeneous structure that is desirable in terms of building physics, in which all components have a similar value for the water vapour diffusion resistance.

Flame retardant: polystyrene and Resol rigid foam

The most widely used insulation material is expanded polystyrene (EPS for short). Its popularity is based on its high insulation performance and cost-effectiveness; however, EPS-based ETICS only achieve the building material class B in terms of fire protection. The thickness of the insulation material also plays a role in the classification: for insulation thicknesses ≥ 100 mm, building owners must take additional measures to achieve building material class B1. The EPS insulation material must be combined with non-combustible mineral wool insulation to create barriers in the event of a fire. For this purpose, horizontal fire barriers of mineral wool are applied around the entire building or lintels and reveals are insulated with mineral wool.

ETICS can also contain the insulating material Resol rigid foam. This is characterized by excellent thermal conductivity values; it also performs better than EPS in terms of fire protection. Resol rigid foam is categorized in Euroclass B-s1, d0, which corresponds at least to the fire safety level of building material class B1. Up to an insulation thickness of 240 mm, building owners do not need to take any additional fire protection measures.

Wood fiber-based ETICS systems are now also available on the market. They are of interest to environment-conscious building owners, but only achieve building material class B2 in terms of fire protection.

Extension of the previous protection targets includes protection of socket parts against fire

The prevailing structural fire protection measures are focused on fire protection in residential rooms, i.e. they primarily serve to prevent fires from spreading from the inside of the building to the façade. The whole facade is considered. The regulations that provide for either lintel protection above every opening in the outer wall or horizontally surrounding fire barriers on every second storey remain in place, as they have proven to be effective.

The new regulation incorporates a further hazard scenario into the structural fire protection of ETICS: the "socket fire", where a fire load is assumed to be carried towards the facade from the outside at the ground connection area. For this reason, additional fire protection measures in the form of fire barriers will have to be taken in future in order to create a protection zone between the socket part of the building and the third storey, regardless of the thickness of the insulation material. This is intended to prevent fires, such as those involving parked vehicles, rubbish containers or bulky waste, from spreading to the buildings. A total of three additional fire barriers are installed in the socket area all around the building; the first at the lowest part of the ETICS, the second at the height of the ceiling of the first storey and the third at the height of the ceiling of the third storey.

The current regulation therefore requires additional fire barriers of mineral wool for all insulation thicknesses (one fire barrier at the socket part, one fire barrier between the ground floor and first storey, one additional fire barrier between the second and third storey and one fire barrier at the upper top). 

Escape and rescue routes, such as passageways, arcades and external staircases also require special attention. These should generally be equipped with non-combustible insulation and a mineral render system. The same applies to soffits (e.g. garages, arcades, recesses, balconies, loggias). 

Fire barriers in ETICS must be constructed or bridged with non-combustible insulation materials. The vertical fire barrier must be at least 200 mm wide and extend beyond the thickness of the firewall. The exact position of the firewalls must be determined in advance of construction or specified by the construction management. This is regulated in § 30 of the Model Building Code (MBO). Region-specific deviating requirements for the design of fire flashovers are possible. For full information request technical advice or refer to the Technical System Information No.  6 of the German ETICS Association.

Conclusion

All ETICS are subjected to fire protection tests before they are approved by the building authorities. This means that only tested systems are placed on the market. For facades insulated with EPS systems, additional fire protection measures must be taken depending on the building height, insulation thickness and building utilization. Only fully mineral systems based on mineral wool achieve the "top grade" A1.

For fire protection, the building height is important: the higher the building, the stricter the fire protection requirements. In the case of residential and office buildings of building classes 1 to 3 (i.e. buildings where the floor of the top lounge does not exceed the height of 7 meters above medium ground level), the building regulations stipulate a standard (normal) flammable outer wall cladding. A thermal insulation composite system of up to 100 mm thickness should therefore be implemented without additional fire protection measures. Above 22 meters, systems of building material class A must generally be used; details are regulated by the respective regional building regulations.

Saint-Gobain Weber attaches great importance to the highest possible security, both in internal processes and in Weber systems and the associated recommendations for implementation... Regardless of the building class, Weber therefore recommends "flame retardant" as a minimum level of fire protection.

It is also important that the building material classes do not refer solely to the insulation material. The building authority approval is only valid if the complete system with all individual components is used. Only in this case, you can rely on the specified building material class of the thermal insulation composite system.