What are fire rated windows

• 13 February 2025
• News

Fire rated windows are glazing systems designed to withstand fire conditions for a defined period — typically 30, 60 or 120 minutes — while preventing the spread of flames, smoke and heat between spaces. For architects, builders and property owners specifying fire rated windows, understanding the available classifications and compliance requirements is essential. This guide covers everything you need to know, including the fire rated steel window systems manufactured by the team of specialists at Crittall Windows.

The fundamentals of fire rating in windows

What is window fire rating?

Fire rating refers to the amount of time a window can withstand exposure to fire conditions while maintaining its structural integrity. The rating is determined through a series of rigorous testing procedures that measure how effectively the window prevents the spread of fire, passage of smoke and transmission of heat between spaces.

Understanding fire rating classifications

Fire resistance levels

Fire-rated windows are classified according to their performance in standardised tests, with ratings typically expressed in minutes – typically, 30, 60 or 120. These ratings indicate how long the window can maintain its integrity under fire conditions. For example, an FD30 rating means the window can withstand fire for a minimum of 30 minutes.

Performance criteria

Fire rated windows must meet three performance criteria during testing. They must:

• Demonstrate their integrity by preventing the passage of smoke and flames between spaces.
• Provide adequate insulation by restricting heat transfer to protect occupants and the property.
• Maintain structural stability even when exposed to high temperatures.

Fire regulations and compliance

Fire safety regulations in new build homes and commercial properties require specific minimum fire ratings based on several key factors. These requirements vary depending on building usage and occupancy levels, distance from means of escape, overall building height and size, and proximity to other structures. Each of these elements must be carefully considered when specifying fire rated windows.

Considerations for different settings

Different environments demand varying levels of fire protection to ensure occupant safety and to reduce the spread of flames. Commercial spaces, educational facilities and healthcare establishments require higher ratings due to increased occupancy and complex evacuation requirements so there is a clear and safe means of escape. Residential properties are not exempt — fire rated windows are increasingly specified in new build homes, renovations and conversions, and Crittall Windows supplies fire rated solutions for both residential and commercial applications.

An approach to fire safe window design

Innervision® Fire Rated screens demonstrate how modern fire safety can complement contemporary design. These systems offer FD30 fire rating and achieve impressive insulation properties, while maintaining the signature slim profiles that Crittall Windows’ products are renowned for.

Glazing design that doesn’t compromise performance

The Innervision® range proves that fire safety doesn’t mean sacrificing impressive aesthetics. This is because large fire resistant glazing panels are incorporated into the design, allowing spaces to be flooded with natural light while, at the same time, efficiently protecting homes in the event of a fire.

Benefits of fire rated windows

Enhanced safety features

Modern fire rated windows effectively contain internal fires within designated compartments, preventing fire hazards from spreading between areas. The windows are designed to protect against fire for extended periods, significantly reducing the effects of fire to any occupants.

Long-term value

The benefits of investing in fire rated windows are priceless. Installing products like the Crittall Windows Innervision® range provides complete peace of mind that the appropriate fire safety measures are in place.

From a property owner, architect or builder point of view, this also means that the products installed within commercial or residential spaces remain compliant with current building regulations.

Choosing the right fire rated solution

Fire rated windows are a crucial investment in any renovation or new build project, offering essential protection to properties in the event of a fire. Crittall Windows’ commitment to combining safety with style is evident in the Innervision® Fire Rated range, providing architects, builders and property owners with solutions that don’t compromise on design or safety.

Frequently asked questions

Can fire rated doors include glazing?

Yes. Fire rated door and screen systems can incorporate glazed panels, provided the glazing is tested and certified as part of the complete assembly. The Crittall Innervision® Fire Rated range is designed specifically as a glazed screen system carrying an FD30 rating — combining full-height glazing with certified fire performance, without compromising on light or aesthetics.

What does a 30-minute fire rating mean?

A 30-minute fire rated window or screen — such as the FD30-rated Innervision® system — is tested to withstand fire conditions for a minimum of 30 minutes. During this period the system must maintain its integrity by preventing the passage of flames and smoke, provide insulation by restricting heat transfer, and retain its structural stability.

Are fire rated windows suitable for residential use?

Yes. Whilst fire rated glazing is commonly associated with commercial, educational and healthcare settings, Crittall Windows also manufactures fire rated solutions for residential applications. The Innervision® Fire Rated range is available for both residential and commercial projects, combining the safety performance required by building regulations with the slim steel profiles associated with Crittall design.

Get in touch today to discuss your project with a member of the Crittall Windows’ team.