02 Jun Specification, selection & installation is critical
This article was created from A Guide to Best Practice in the Specification and Use of Fire-Resistant Glazed Systems, a well-respected guide produced by the Glass and Glazing Federation (GGF) which represents companies that manufacture, supply or install glass and glazing products throughout the world. Like Fire Middle East magazine, the GGF promotes best practice and the highest technical and health & safety standards.
The occurrence and development of fire are essentially unpredictable and uncertain, and its effects can be catastrophic for both life and property.
Fire-resistant glazing provides excellent protection for lives and property in the event of fire. The fire environment is a hostile one for all materials and its occurrence and propagation is essentially unpredictable with uncertain outcome. It is therefore critical that the specification, selection, and installation of fire-resistant glazing are all carried out with close attention to detail.
Fire-resistant glass can only achieve its designed performance when it is part of a complete fire-resistant glazed system. This means that all component parts, such as the glazing seal, beads, fixings and frame material, must all be compatible and work together to achieve the required performance. The fire-resistant glazed system must also be installed as tested or assessed by an appropriately qualified authority. Different types of fire-resistant glass may require different glazing details, e.g. the glass edge cover, which must not be changed or assumed to apply to other glass types.
Each glass type has its own characteristics, which can give rise to significant differences in fire behaviour. Fire performance depends on the glass type and the fire-resistant glazed system design and construction. Also, the approved fenestration layout and glass pane sizes generally vary according to the particular approved glazed system being considered.
The list below provides a general description of the performance of various types of glass offered by GGF members.
Wired
the glass fractures and the integral wire mesh holds the glass together to maintain the integrity performance.
Ceramic
the glass has a near zero thermal expansion coefficient and a very high softening point, which maintains integrity performance.
Heat Soaked Modified Thermally Toughened Soda Lime Silicate Safety
the toughening process develops high stresses, and these retain the integrity of the glass on exposure to fire.
Modified Toughened Soda Lime Silicate Safety
the toughening process develops high stresses, and these retain the integrity of the glass on exposure to fire.
Resin Laminated
the integrity of these types of glass is achieved through the use of a resin-based interlayer formulated to have resistance against fire and flaming.
Modified Toughened Laminated
the toughening process develops high stresses and these retain the integrity of the glass on exposure to fire.
Thermally Toughened Borosilicate Safety
these glass types remain intact due to its composition and low thermal expansion to provide the required integrity performance.
Laminated Intumescent
these types have an intumescent interlayer(s) formulated to turn opaque and swell on exposure to fire and provide the required fire-resistance performance.
Gel Laminated
these types have an intumescent interlayer(s) formulated to turn opaque and swell on exposure to fire and provide the required fire-resistance performance.
Fire-resistant insulating glass units
Insulating glass units (IGUs) do not offer fire-resistance unless they incorporate one or more of the types of fire-resistant glass shown and have been fire performance tested. The GGF provide industry guidance to insulating glass unit manufacturers regarding their compliance with EN1279 and the relevant attestation levels for fire-resistant IGU’s. Important considerations are that:
- The IGU must have its own fire test or assessment report based on test evidence
- In some cases, it must be possible to confirm the direction of use before installation
- The components used in the IGU must be proven by test or assessment the fire-resistant glazing system must be appropriate for the application of the IGU, e.g. drained and ventilated for use in external façade applications
In all cases, the manufacturer/supplier must be consulted for evidence in support of the fire-resistant glazed system. Special glass units containing integral Venetian blinds may also be available fire rated.
Horizontal and inclined glazing systems
Fire-resistant glazed systems are most often used in a vertical orientation. However, there are some specialist approvals available for application in the sloped and horizontal orientations, including fire-resistant floor constructions.
A number of manufacturers have tested and approved systems available for both internal and external applications. These structures must also be able to withstand the imposed loads defined in BS NA EN 1991-1-1: UK Actions on structures. General actions. Densities, self-weight, imposed loads for buildings. Specific details must be obtained directly from the manufacturer/supplier of the system.
Decorative treatments on glass
It must not be assumed that decorative effects can be applied to all types of fire-resistant glass without affecting fire-resistance. Some types of glass may be decorated with surface treatments, e.g. sandblasting, screen printing, without impairing their fire-resistance performance. Others cannot be surface treated. In all cases, specialist advice of the manufacturer/supplier must be obtained to ensure that the proposed treatment is appropriate and that relevant evidence of performance is available.
Combining other performance requirements
Other performance requirements may be readily integrated into the fire-resistant glazing system specification without compromising fire-resistance performance. This is an increasing requirement as buildings become more complex and the building environment more demanding. This can include a range of different functions (e.g. thermal insulation, safety and security, decoration and privacy). Because of their use in escape and access routes, impact safety and manifestation (i.e. to minimise the risk of people inadvertently walking into a glass partition) are particularly important additional performance requirements.
Additional functions which may be combined with fire-resistance include impact safety; containment (or barrier loading; thermal insulation – low emissivity energy saving and insulating glass units; solar control ; acoustic insulation; resistance against forced entry; explosion and bullet protection (only available when relevant test evidence exists; in addition to certification for fire-resistance).
Here the GGF stresses that consultation with the manufacturer or supplier is essential when identifying additional functions that can be provided with fire-resistant glass
Importance of the glazing seal
Glazing seals play an important role in fire-resistant glazed systems. They are an essential part of the system, and selection of the appropriate glazing seal is influential in ensuring that the performance capability of the full assembly is achieved under fire conditions. An incorrect choice of seals may cause premature failure. The seal must be capable of withstanding the temperatures experienced in fire without igniting, degrading catastrophically or losing strength and adhesion.
The following key rules apply:
- The seals must be compatible with the other system components, especially the fire-resistant glass
- There must be appropriate evidence of fire performance of the glazed system in all cases
- One seal must not be substituted for another without such appropriate evidence.
Suitable seals can be either intumescent or non-intumescent based and are available in a variety of forms.
The combined functions of the glazing seal are as follows:
- Bedding the glass against the retaining bead and minimising the probability of uneven point loading or edge stresses
- Sealing the gap between the glass, the bead and the edge of the frame to prevent the penetration of hot gases and flame
- In the case of intumescent seal types, providing additional protection to the top of a timber bead to lower the risk of bead ignition – a benefit that comes at the expense of gap sealing performance; therefore, both intumescent and non-intumescent seals have been developed for use with integrity-only glass types for both 30 and 60 minute applications.
There is a shared duty of care on all those involved in the specification, testing, supply and installation of fire-resistant glazed systems. It is essential to ensure that the final installed system is fit to protect the building and its occupants against the effects of fire. Critical factors in achieving the intended performance in the event of fire are the quality and the reliability of product performance and satisfactory workmanship on installation.
Download ‘A Guide to Best Practice in the Specification and Use of Fire-Resistant Glazed Systems’ here