Glass and Fire Safety

When designing a new building, we have to comply with a whole series of requirements regarding fire safety that are imposed by EU legislation. Construction materials used for partitions must meet the criteria of specific fire resistance classes, which for some architects can feel as a brake on their freedom of design. A glass partition can provide a solution here, given that even for the top fire resistance classes, a transparent solution is possible using glass.
EU legislation
EU legislation distinguishes a material’s reaction to fire and it’s resistance to fire. A material’s reaction to fire indicates how a material will respond to fire. A distinction is made between fire-resistant materials, inflammable materials and flammable materials. Materials are divided into seven Euroclasses: A1, A2, B, C, D, E and F, where A is the best classification. The following glass products are included in the list of materials that are assigned to class A1 without testing being needed: float glass, patterned glass, heat strengthened glass, thermally toughened glass, chemically toughened glass, glass with an inorganic coating, and wired glass.
A material’s fire resistance is expressed in minutes and indicates how long the material in question resists fire in terms of the following factors: stability, flame integrity and thermal insulation. All materials have a reaction to fire, but only certain products or systems are eligible for a fire-resistance classification. This requirement always relates to a whole building component and not just to a part of it. In the case of glass, the following criteria are assessed:
 flame integrity (E): duration of the period when no flames, smoke or hot gas come through the building element;
 radiation limitation (W): duration of the period when the radiation on the opposite side to the fire does not exceed a specific threshold;
 thermal insulation (I): duration of the period when the temperature on the side not exposed to the fire does not exceed a specific threshold.
The requirements for the building element are the following:
 E (x): the building element is stable and maintains its flame integrity for x minutes;
 EW (x): the building element is stable, maintains its flame integrity and limits the radiation for x minutes;
 EI (x): the building element is stable, maintains its flame integrity and limits the temperature for x minutes.
Glass products with an EI classification, mostly have an EW classification too with a longer duration. This is due to the higher requirements of the EI classification compared to the EW classification with the same time. In addition, the glass must always be installed in a profile with the same classification: provided that the building component is subject to the requirements, fire tests are always performed on the glass and its profile as if they were one unit. The maximum allowed dimensions of this combination always has to be checked.

Choosing the right glass fire rating (Rf)
The Belgian and EU standards give rise to a specific requirement relating to the relevant partition wall. In Belgium this is mostly EI30, EI60, EI120, E30 or E60. This requirement enables you to select the corresponding fire-resistant glass. Then a check must be carried out to see whether the dimensions you need fall within the maximum dimensions, written in the test certificate, and in combination with what type of profile it can be used (wood, steel, aluminium, etc.). AGC Glass Europe has two ranges of fire-resistant glass, each with their own scope.
Pyropane is a toughened fire-resistant glass with a special coating. It can be used for classes E30, E60, EW30 and EW60 or more specifically as a smoke curtain (Pyropane SB 100). Its coating and its resistance to high temperatures mean that in a fire it will hold back much of the radiation energy. This range is – depending on the product – fire-resistant in one or two directions.
Pyrobel or Pyrobelite is a glass consisting of a number of layers of float glass separated by a transparent fire-resistant gel. In case of fire, these intermediate layers will swell up one by one and change into an opaque insulating shell that is fireproof and that considerably limits the transfer of heat. This type of fire-resistant glass can be applied to meet both an EW requirement (EW30, EW60) and an EI requirement (EI15, EI20, EI30, EI45, EI60, EI90, EI120) and is always fire-resistant in two directions. To protect the glass from UV radiation, when it is used in façades it must be combined with at least two polyvinylbutyral (PVB) sheets that act as a UV filter.
To create continuous fire-resistant interior walls in glass, AGC recently launched Pyrobel Visionline. Since vertical frames or profiles there no longer necessary with this product, they can be assembled to create very long glass partitioning walls (Figure 1 – AZ Groeninge hospital in Kortrijk, BE). A silicone joint of 4 mm to 5 mm is then inserted between two fire-resistant volumes. Pyrobel Visionline is available in EI30 and EI60.
Fire-resistant glass such as Pyrobel, Pyropane and Pyrobel Visionline gives architects more freedom to meet the severe requirements relating to fire resistant partitions in their design.

The next issue will discuss Glasstronics, a smart combination of glass and electronics.

Thomas Hens (Technical Advisor, AGC Glass Europe)

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