Recently, we had to face a Project that we had to put into practice some knowledge about the fire protection of the glass. We were making up some solutions whilst how to figure out to choose the best option to our client.
In the end, we solved the problem according to several German’s standard DIN and national regulations. Meanwhile, we have thought that it could be interesting to publish a short entry in this blog explaining it a bit.
We know that fire protection represents an important aspect in the safety of the built environment. It is known that in Germany, the principal fire protection requirements are specified in the Model Building Code (MBO), which forms the basis for the building regulations of the individual federal states (LBO).
According national (Spanish) and international regulations, the building materials and components used in buildings and structures must comply with certain requirements in order to achieve the goal of preventing the spread of fire. To sum up, building materials are divided into the following groups:
- Not readily flammable
Building components are divided into the following groups depending on their ability to withstand fire:
- Highly fire-retardant
The behaviour of glass in fire
We all know that glass is generally incombustible and does not represent a fire load in the event of a fire. It is therefore allocated to building materials class A1 according to DIN 4102-4 and to UNE-EN 13501 and RD 842/2013, October 31th.
It is important to remember that when the glass is exposed to the effects of heat, normal sheet products shatter relatively easily because of their low tensile bending strength in conjunction with their relatively high coefficient of thermal expansion. Therefore, glass is unsuitable for use in constructions designed to enclose an interior space and prevent the spread of fire, so, in order to obtain glass that provides effective fire protection, its breakage due to heat must either be ruled out or compensated for in some way.
Two types of glass are normally used for glass constructions: no the one hand, soda-lime-silica glass to DIN EN 572-1, on the other, borosilicate glass to DIN 1748-1-1. The chemical and physical properties of these glasses depend on their composition.
So-called fire-resistant glasses are non-regulated building products in the meaning of Germany’s or European’s building regulations. As said before, they deviate considerably form the technical rules specified in Construction Products List A part 1.
Class E glazing, despite the effects of fire, remains transparent and intact depending on the form of construction. This class fulfils the sealing requirements even when installed as single glazing. In principle, this form of fire-resistant glazing prevents the passage of smoke and flames only. No requirements are specified regarding the transmission of heat and the ensuring radiant heat.
Class EI glazing provides additional protection against the passage of heat radiation, as well as preventing the spread of smoke and flames. The temperature on the side no directly exposed the fire may not increase by more than a certain amount. The improvement in the total thermal resistance is achieved by a multi-ply construction with special interlayers that foam up due to the effects of heat.
To conclude, we show you the next image:
- Class E: fire-resistant glazing class E (G) prevents the passage of smoke and flames, but not the transmission of heat radiation (Left)
- Class EW: Fire-resistant glazing class EW prevents the passage of smoke and flames and reduces the transmission of heat radiation.
- Class EI: Fire-resistant glazing class EI (F) prevents the passage of smoke, flames and heat radiation.
Prefabricated panes of glass used for fire-resistant glazing
Class EI glazing normally consists of at least two panes of float or toughened safety glass that are separated by a fire-resistant layer. When exposed to heat, the pane on the fire side breaks. The gel, the fire-resistant layer, foams up and insulates the rest of the construction against the fire. Multi-ply glass blocks with a suitable web thickness and internal voids may also be used.
Class E glazing employs special single glazing that, owing to its chemical composition and thermal toughening, is able to be used as part of a fire-resistant glazing unit providing sufficient resistance to the fire. This glazing system can satisfy class E requirements when it consists of a least two panes of float or toughened safety glass separated by a fire-resistant layer or by a cavity filled with air or a special gas. In the event of a fire, the fire-resistant layer also foams-up. Glass blocks may also be used but the form of construction must be taken into account.