Fire rated glass is an essential component of any passive fire protection system. It is used for providing protection to the opening of a fire barrier, such as fire doors or windows. The purpose of a passive fire protection system is to contain the spread of fire and slow it down so that people who are in the building have time to escape safely.
In this article, we shall discuss the difference between two broad categories of fire rated glass which are fire protective glazed glass and fire resistive glazed glass. We shall then discuss common fire rated glass products.
(Note: The term “Lite” refers to a single unit of glass)
The difference between fire protective glass and fire resistive glazing
Essentially, the difference between the two categories is the extent to which they provide protection.
Fire-protective glazed glass
Fire protective glazed glass has glazing that prevents the smoke and flames from spreading. Materials used in fire protective glazed glass include glass ceramics, traditional wired glass and specially tempered glass. Fire protective glazing comes with ratings that range from 20 minutes to 3 hours.
Fire resistive glazed glass
Fire resistive glass prevents the smoke and flames from spreading and also blocks the transfer of heat via conduction and radiation.
These products are multi layered and incorporate multiple glass layers with the space between each glass layer filled with fire resistive inter-layers. Fire resistive glass is usually suitable for areas of a given building that are designated as “fire resistant” by building codes. Examples of such areas include staircases, fire exits or fire barriers that are protecting crucial structural integrity points.
Types of Fire rated glass
Polished wired glass
Polished wired glass is a very common example of fire rated glass. It has been used in passive fire protection systems for over 100 years. Wired glass typically has a rating of 45 minutes. It usually comes in sizes of 100 square inch lites. Wired glass is a cost effective solution in developing a passive fire protection system, but its resistance to impacts is very low. Its use has been prohibited by the IBC since 2006. Polished wired glass comes in the category of fire protective glazed glass.
Glass ceramic is another example of fire rated glass. Glass ceramic looks almost exactly like normal window glass, which makes it aesthetically pleasing as well. The fire rating for glass ceramic products ranges from 20 minutes to almost 3 hours. The dimensions of a glass ceramic lite are usually 24 square feet. Glass ceramics can resist the thermal shock that results from water that is coming from fire hoses or sprinklers. There are variants of glass ceramics that are highly impact resistant. They have a Category II impact safety rating. A Category II rating indicates that the glass can endure the impact of a fast moving, full-grown adult. Glass ceramics are an example of fire protective glazed glass.
Glass wall panels
Fire rated glass wall panels are another product. These are in the category of fire resistive glazed glass, i.e. they also prevent the transfer of heat via conduction and radiation. These can be used for installing glass doors and walls, making them aesthetically pleasing as well. Their fire resistance is the equal of any normal solid wall. Therefore fire rated glass wall panels result in a passive fire protection system that can be extremely successful. Fire rated glass panels also come with Category II impact rating.
Specially tempered glass is a category of fire rated glass that has a 20-minute rating. Tempered glass cannot resist thermal shock, which is why their use is restricted to fire doors with a rating of 20 minutes.