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Innovations in Fire Rated, Temperature Rise Glass Doors

Innovations in Fire Rated, Temperature Rise Glass Doors

Hard to believe, but there was once a time when adding a small piece of wire or ceramic glass in a fire rated door was considered new or even innovative because it allowed for vision as well as fire protection.  Fast forward to today where the IBC has imposed significant limitations to wire, ceramics and all fire protective glazing used in doors rated over 45 minutes.  With 80% of the states adopting the 2012 and 2015 IBC, this size limitation on fire protective glass in 60-90 minute temperature rise glass doors becomes more pronounced because the code limits their size to 100 sq. inches regardless if the building is fully sprinklered.  With designers and building occupants demanding maximum views in their fire doors, the glazing products used in these doors had to evolve as well to meet the code requirements.

Increasing transparency with the help of fire rated glazing is easy to accomplish in 20 and 45 minute doors, where the door is expected to only compartmentalize smoke and flames.  However, in 60 and 90 minute doors that are required to compartmentalize smoke, flames and limit the heat transfer on the non-fire side, this is more challenging.  Known as temperature rise doors, these doors carry a temperature rise rating in addition to the hourly fire rating.

Temperature rise ratings for fire doors are either 250 degrees F, 450 degrees F or 650 degrees F, indicating the maximum rise above ambient temperature on the non-fire side measured during the first 30 minutes of the fire endurance test.  In both the UL 10C and NFPA 252 test standards, thermocouples are placed on specific points on the door:

UL 10C Section 6.2.  Unexposed surface temperatures shall be taken at no less than three points, with a minimum of one thermocouple each in 16-ft2 (1.5 m2) area of the door.  Thermocouples shall not be placed over reinforcements extending through the door, over the glass panels, or nearer than 12 in. (305 mm) from the edge of the door.

NFPA 252 Section Thermocouples shall not be located over reinforcements extending through the door, over vision panels, or within 305 mm (12 in.) of the edge of the door.

Temperature rise doors rated 60-90 minutes are typically made of steel with an opaque, insulating core to limit heat transfer. Where glazing is incorporated, it is usually a fire protective product that is limited to 100 sq. inches to limit the passage of heat through the glass.  Typically, wire or ceramic in limited sizes have been used due to their stability and capability to withstand the hose stream in this small size even though these products has no ability to block radiant heat.

Adding glazing in excess of 100 sq. inches to 60-90 minute temperature rise doors was impossible until the introduction of fire resistive glazing tested to ASTM E-119/UL 263/NFPA 251.  This type of glazing is capable of limiting the temperature rise on the non-fire side to less than 250 degrees F.  While temperature rise doors are not exactly new, having full-vision door lites incorporated in the door assembly is relatively new, and is still considered a niche or specialty product.  There are many door manufacturers that offer opaque temperature rise doors or with a 100 sq. inch vision lite as a commodity product.  In contrast, there are only a handful of manufacturers that offer temperature rise doors with full vision glazing because of the unique challenges that it can present.

Size and Weight Considerations – and Design Opportunities

The obvious challenge is the thickness and weight of using fire resistive glazing.  There are 2 options available in the market today that meet the ASTM E-119/UL 263/NFPA 251 requirement – one is a tempered fire resistive unit and the other is an annealed multilaminate.

For 60 minutes, the tempered fire resistive units are at 1-1/8” / 9 lbs. per square foot, while the annealed multilaminates start at 7/8” / approx. 11 lbs. per square foot.  At 90 minute ratings, the tempered fire resistive units are at 1-1/2” / 12 lbs. per square foot, while annealed multilaminates start at 1-7/16” / approx. 18 lbs. per square foot.  If you are looking to have full-vision in a 3 ft. wide x 7 ft. high 90 minute temperature rise door for example, the weight of the glass can over 200 lbs.  If the door and hardware are not properly engineered to tested with these weights, it will an issue.

Using a fire rated glass and framing manufacturer that offers fully listed and labeled glazed door assemblies is critical at these higher ratings. Today, 60-90 minute temperature rise doors are available up to 10 ft. high, with multiple fire rated hardware options and finishes.  The technology on fire rated doors has improved so much in the last 10 years that hardware manufacturers are offering more fire rated hardware options to accommodate the size and weight that these doors may impose without necessarily compromising on design.

These 9-ft high 60 minute temperature rise pair doors matches the height of the adjacent 1-hour butt-glazed wall at the University of Wisconsin School of Business Learning Commons in Madison, WI. This eliminates the need to add a transom to the door assembly, which appealed to the architect.


Before, steel temperature rise doors with a painted finish was the only available choice.  Today, designers can choose between anodized finishes, stainless steel, wood veneer, brass, and more. All of these developments allow designers to have a clear view door with sleek and elegant aesthetic while meeting the temperature rise requirements of the project.

90-minute temperature rise pair doors with a clear anodized finish at Harvard Business School’s Klarman Hall in Boston, MA.


90 minute temperature rise pair doors with stainless steel finish at CUNY School of Law in Long Island City, NY.


90 minute temperature rise pair doors with custom brass cladding at UC Berkeley Doe Library in Berkley, CA.


90 minute temperature rise pair doors with a wood veneer finish at the Reid Hospital in Richmond, VA.

Multi-tasking Door Assemblies

In addition to aesthetics, full-vision fire rated glass doors have also evolved to perform multiple functions in one assembly.

For example, there are fire rated, temperature rise doors that provide hurricane performance as well.  Other than meeting fire and temperature rise requirements up to 90 minutes, these doors are tested to TAS 201, 202 and 203 and have complete Florida Product Approvals, Texas Department of Insurance Approval and UL Certifications.

90 minute, temperature rise and hurricane rated pair doors at the Las Olas Beach Club in Ft. Lauderdale, FL.

Fire rated, temperature rise doors up to 90 minutes with ballistic performance are also available.  Today, there are full vision fire rated doors that meet UL 752 Level 1, 2 and 3.  Higher ballistic ratings can be engineered depending on the requirement. In those cases, it is best consult with the manufacturer early in the project phase.

60 minute, temperature rise and ballistic rated pair doors for a private office in San Francisco, CA.

Other additional performance options include forced entry, acoustic, privacy, and more.  For those architects looking exercise their creativity, decorative options on the glass and the door are also available.

Indeed, fire rated temperature rise glass doors have come a long way.  As designers and building owners continue to demand better performance and aesthetics, fire rated glass and framing manufacturers will continue to offer innovative products that can meet or exceed their expectations while maintaining full code compliance. Always check the listing and testing of these specialty doors for a trouble-free project.


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