A specification guide to vision panel (lite kit) sizes, fire-rated glazing requirements, glass types, and maximum glass area allowances by fire rating for commercial door assemblies.
This guide answers: What are the size and fire rating requirements for vision panels in commercial doors?
Overview of Vision Panels in Commercial Doors
A vision panel (also called a vision lite, door lite, or lite kit) is a glazed opening cut into a commercial door to provide visibility through the door. Vision panels serve safety, security, and wayfinding functions: they allow occupants to see approaching traffic on the opposite side of the door, reducing collision injuries; they provide visual confirmation of room status; and they admit natural light into interior spaces.
Vision panels in commercial doors are subject to building code requirements governing maximum glass area, glazing type, and fire rating. In fire-rated assemblies, the vision panel must be tested and listed as part of the complete fire-rated door assembly. CDF Distributors configures lite kit options as part of its door assembly offerings, and ProBuilder validates that the selected glazing meets the requirements of the specified fire rating.
Standard Lite Kit Sizes
Vision panel openings are specified by the visible glass size (daylight opening) and are available in standard configurations. The most commonly specified sizes for commercial doors include:
- Narrow lite: 6 inches wide by 27 inches tall — used in corridor doors where limited visibility is sufficient
- Half lite: 24 inches wide by 30 inches tall — standard office and classroom visibility
- Full lite: 24 inches wide by 60 inches tall — maximum visibility for vestibule and entry doors
- Custom sizes: Available to specification within the constraints of the door construction and fire rating
Fire-Rated Glazing Requirements
When a vision panel is installed in a fire-rated door, both the glazing material and the lite kit frame must be tested and listed for the specified fire rating. Fire-rated glazing is tested under UL 9 (fire endurance) and UL 10C (positive pressure fire test). The glazing must maintain its integrity for the full duration of the rated time period without allowing passage of flames or hot gases.
The maximum allowable glass area in a fire-rated door varies by fire rating. Higher fire ratings impose stricter limits on glass area. The following are the standard maximum glass size allowances by fire rating:
- 20-minute rating: Up to 1,296 square inches (maximum dimension 54 inches) of fire-protective glazing. Tempered glass is permitted at this rating level with sprinkler protection.
- 45-minute rating: Up to 1,296 square inches (maximum dimension 54 inches) of fire-protective glazing. Fire-rated ceramic glazing (e.g., SuperLite, FireLite) is typically required.
- 60-minute rating: Up to 100 square inches (maximum dimension 10 inches) of fire-protective glazing per NFPA 80, unless fire-resistive glazing is used. Fire-resistive glazing (which blocks radiant heat transfer) may allow larger lites up to 1,296 square inches.
- 90-minute rating: Up to 100 square inches (maximum dimension 10 inches) of fire-protective glazing per NFPA 80. Fire-resistive glazing may allow larger lites depending on the tested assembly listing.
- 180-minute rating: Vision panels are generally not permitted in 180-minute (3-hour) rated doors. Where required by specific tested assemblies, only fire-resistive glazing in very limited sizes may be used, subject to the manufacturer's listing.
Fire-Protective vs Fire-Resistive Glazing
Understanding the distinction between fire-protective and fire-resistive glazing is essential for correct specification.
Fire-Protective Glazing
Fire-protective glazing prevents the passage of flames and hot gases but does not block radiant heat transfer. It is rated under UL 9 and tested to NFPA 252 / UL 10C. Fire-protective glazing is acceptable in doors rated up to 90 minutes but is limited to 100 square inches in 60-minute and 90-minute applications (per NFPA 80). Common fire-protective glazing types include wired glass and ceramic glazing products.
Fire-Resistive Glazing
Fire-resistive glazing blocks both flames and radiant heat transfer. It is rated under UL 9, UL 10C, and ASTM E119 (the wall fire test). Because fire-resistive glazing blocks radiant heat, it can be used in larger sizes in 60-minute and 90-minute rated doors where fire-protective glazing would be limited to 100 square inches. Fire-resistive glazing products are typically multi-layered assemblies with intumescent interlayers.
Glass Types for Vision Panels
Several glass types are used in commercial door vision panels, each with different fire rating capabilities, safety characteristics, and cost points.
Wired Glass
Wired glass contains an embedded wire mesh that holds the glass in place when it cracks under heat exposure. Wired glass was historically the standard fire-rated glazing for door lites. However, wired glass has lower impact resistance than tempered or ceramic alternatives, and many jurisdictions and specifications now restrict or prohibit its use in doors on accessible routes or in locations subject to human impact (per CPSC 16 CFR 1201 and ANSI Z97.1 safety glazing requirements). Where still permitted by code, wired glass remains a low-cost option for fire-rated vision panels.
Ceramic Glazing
Ceramic glazing (products such as FireLite and SuperLite-I) is a fire-protective glass-ceramic material that withstands high temperatures without cracking. Ceramic glazing meets both fire rating and safety glazing (impact) requirements, making it the most commonly specified fire-rated glazing for commercial door lites. It is available in ratings from 20 minutes through 90 minutes and meets CPSC 16 CFR 1201 and ANSI Z97.1 safety standards.
Tempered Glass
Tempered glass is heat-treated for impact resistance and breaks into small granular pieces rather than sharp shards. Tempered glass is the standard for non-fire-rated vision panels and is accepted in 20-minute rated doors when sprinkler protection is present. Tempered glass is not suitable for fire ratings above 20 minutes because it loses structural integrity at relatively low temperatures.
CDF Lite Kit Configurations and ProBuilder Glazing Options
CDF Distributors offers lite kit configurations as part of its complete door assemblies. When building an assembly in ProBuilder, specifiers select the lite size, glazing type, and fire rating. ProBuilder validates that the selected glazing meets the requirements of the specified door fire rating, including maximum glass area restrictions.
For non-rated doors, CDF offers tempered glass lites in standard and custom sizes. For fire-rated assemblies, CDF supplies ceramic and fire-resistive glazing options that comply with NFPA 80, UL 9, and UL 10C requirements. All fire-rated lite kits include listed frames and glazing materials as part of the tested assembly.
Configure Your Door Assembly
CDF's ProBuilder tool lets you configure vision panels as part of a complete door assembly. Select from standard and custom lite sizes with validated fire-rated glazing options. ProBuilder ensures your glazing selection is compatible with the specified fire rating. For assistance, call (855) 769-9895 or email sales@cdfdoors.com.
Frequently Asked Questions
What is the maximum glass size in a 90-minute fire-rated door?
Per NFPA 80, fire-protective glazing in a 90-minute rated door is limited to 100 square inches with a maximum dimension of 10 inches. Fire-resistive glazing (which blocks radiant heat) may allow larger vision panels depending on the specific tested assembly listing.
Can I use tempered glass in a fire-rated door?
Tempered glass is only accepted in 20-minute fire-rated doors when sprinkler protection is present. For 45-minute, 60-minute, 90-minute, and 180-minute ratings, fire-rated ceramic or fire-resistive glazing is required.
Is wired glass still allowed in commercial door lites?
Wired glass is still permitted in some fire-rated applications, but it does not meet modern safety glazing impact standards (CPSC 16 CFR 1201). Many jurisdictions and specifications prohibit wired glass in locations subject to human impact or on accessible routes. Ceramic glazing has largely replaced wired glass as the standard fire-rated door lite material.
What is the difference between fire-protective and fire-resistive glazing?
Fire-protective glazing prevents passage of flames and hot gases but does not block radiant heat. Fire-resistive glazing blocks both flames and radiant heat. Fire-resistive glazing can be used in larger sizes in 60-minute and 90-minute rated doors where fire-protective glazing is limited to 100 square inches.
Are vision panels allowed in 180-minute (3-hour) fire-rated doors?
Vision panels are generally not permitted in 180-minute rated doors. Where specific tested assembly listings allow glazing, only fire-resistive glazing in very limited sizes is permitted. Consult the door manufacturer's listing for specific allowances.
Does CDF ProBuilder validate fire-rated glazing selections?
Yes. CDF's ProBuilder configuration tool validates that the selected lite size and glazing type are compatible with the specified fire rating. ProBuilder ensures the complete assembly—door, frame, glazing, and hardware—meets NFPA 80 and UL listing requirements.
What lite sizes does CDF offer for commercial doors?
CDF offers industry standard sized lite kits. Custom sizes are available within the constraints of the door construction and fire rating. All sizes are configurable in ProBuilder.
About This Guide
This guide reflects CDF Distributors' standard specifications and field-tested recommendations used by commercial contractors nationwide. The information is provided for specification and selection purposes. Always verify requirements with the Authority Having Jurisdiction (AHJ) for your project location.
For questions or to order a complete door assembly, contact CDF at (855) 769-9895 or sales@cdfdoors.com. Configure your assembly online at ProBuilder: cdfdistributors.com.
