The Code Corner

Glass and Glazing

According to the Glass Manual, published by the Glass Association of North America (GANA), glass has been around for more than 4,000 years.  Glass allows daylight in and allows building occupants to view the outside world while still maintaining an envelope to separate inside from outside.  However, the use of glass in buildings presents issues that must be addressed, such as energy efficiency, fire protection, and life safety.  The International Building Code (IBC) covers all three of these areas.

The IBC establishes energy efficiency requirements through its reference to the International Energy Conservation Code (IECC) in Chapter 13.   For fire protection, Chapter 7 covers requirements for glazed openings in exterior walls and interior partitions.  Openings are discussed in detail in The Code Corner article Nos. 34 and 35, “Openings” Parts 1 and 2.  For this article, only the third area, life safety, will be discussed, which is covered in Chapter 24.  For glazing in elevator cars and hoistways, see The Code Corner No. 38, “Elevators.”

The terms glass and glazing have similar meanings and are frequently used interchangeably, but they do describe different things.  Glass is the material itself, whereas glazing, the noun, refers to any material used as an infill panel, whether it is glass, plastic, or some other material, which is installed in an opening.  Glazing, the verb, is defined by GANA as the “process of installing an infill material into a prepared opening in windows, door panels, partitions, etc.”

The life safety aspect of glass and glazing can be separated into two areas: structural loads and impact loads.  Although an impact load is a form of structural load, it is distinguished as a separate category due to its unique application requirements in the IBC.  There are two types of impact loads addressed by the IBC:  human impact loads and wind-borne debris impact loads.  In the IBC, structural loads are used to determine glass thickness.  For glazing sloped more than 15 degrees from vertical, the structural loads consist of wind, snow, seismic, and dead loads.  For vertical glazing of 15 degrees or less from vertical, the only structural loads considered are the wind and seismic loads.  Because the determination of glass thickness is a complex process, it should be accomplished by a registered structural engineer; therefore, this article will only address the basic concepts of glass structural design.

Glass is required to be provided with a manufacturer’s mark indicating glass type and thickness.  The marking may be omitted if approved by the building official and an affidavit from the glazing contractor is provided indicating that the glass conforms to the construction documents and the requirements of the IBC.  Tempered glass¹ must be permanently marked (e.g. acid or laser etched, sandblasted, ceramic fired, or embossed), except that tempered spandrel² glass, which may be provided with removable paper labels.

The IBC references ASTM E 1300, Standard Practice for Determining Load Resistance of Glass in Buildings.  This standard uses wind with a duration of 3 seconds as the basis of determining the maximum load resistance of glass.  Factors affecting load resistance of glass include the dimensions of the lite, the thickness of the glass, and the number of supported glass edges.  This load resistance must equal or exceed the calculated wind load determined per Section 1609 of the IBC.

Section 2403.2 states that if any edge of a glass pane is unsupported, or if the loads on the glass are unusual, then detailed drawings and analysis or test data are required.  A firmly supported edge is one where the framing member prevents the edge from deflecting more than 1/175 of the glass edge or ¾ inch, whichever is less.  As mentioned earlier, one of the factors affecting the load resistance of glass is the number of supported edges.  ASTM E 1300 provides load charts for glass supported on four sides to one side, which would contribute to the analysis.  Butt-glazed joints would be considered as unsupported edges.

While on the subject of butt-glazed units, Section 2403.4 addresses adjacent unsupported glass edges that are near an interior walking surface.  The provision requires that if a 50 plf load is applied to any point along one of the edges to a maximum height of 42 inches, the deflection cannot be greater than the thickness of the glass panel (See Figure 1).  This eliminates the possibility of someone leaning against one panel, causing it to deflect, and allowing someone to place fingers or other objects within the gap created.

Figure 1 - Deflection of interior butt-glazed panels.

Wind-Borne Debris Resistance

Impact loads created by wind-borne debris are only applicable to structures constructed within wind-borne debris regions.  Chapter 2 defines wind-borne debris regions as areas within 1 mile of a coastal high water line where the ultimate design wind speed is 130 mph or greater, areas where the ultimate design wind speed is 140 mph or greater, or Hawaii.  Design wind speeds are determined per Figures 1609A and 1609B, depending on the risk category of the structure per Table 1604.5.  Essentially, most glazing in structures along the Gulf and Atlantic coasts are subject to requirements for wind-borne debris impact.

To qualify for debris impact resistance, glazing must either be impact resistant or include a permanent impact-resistant covering that can protect the glazed opening.  The standards to test for impact resistance are ASTM E 1886, Test Method for Performance of Exterior Windows, Glazed Curtain Walls, Doors and Storm Shutters Impacted by Missiles and Exposed to Cyclic Pressure Differentials, and ASTM E 1996, Specification for Performance of Exterior Windows, Glazed Curtain Walls, Doors and Impact Protective Systems Impacted by Windborne Debris in Hurricanes.  If a glazed opening is within 30 feet of the grade, then the glazing must pass the large-missile test of ASTM E 1996.  If the glazed opening is greater than 30 feet above the grade, then the glazing need only pass the small-missile test of ASTM E 1996.  The IBC has some exceptions to these requirements, and also provides some substitutions that modify the application of ASTM E 1996.³

Human Impact Resistance

Glazing required to resist human impact needs to comply with the provisions of Section 2406, which requires testing in accordance with Consumer Product Safety Commission (CPSC) 16 Code of Federal Regulations (CFR) Part 1201, Safety Standard for Architectural Glazing Material.  Glazing not located in doors or in wet areas, such as hot tubs, bathtubs, showers, and saunas, may comply with ANSI Z97.1, Safety Glazing Materials Used in Buildings—Safety Performance Specifications and Methods of Test.  Both the Federal and ANSI standards use similar impact test stands (See Figure 2).

Figure 2 - Impact test stand per CPSC 16 CFR Part 1201.

The basic test involves raising the impactor—a punching bag filled with lead shot weighing 100 pounds.  To qualify as safety glazing, the test specimen must not, at a minimum, develop a hole in which a 4-pound 3-inch solid steel sphere could pass.  After the test, the specimen is rotated to the horizontal position and the sphere is placed in the opening.  If after one second the sphere has not dropped through, the specimen is deemed to have met the impact criteria.  Glass with a Category I rating (Class B per ANSI Z97.1) has passed the test when the impactor is raised 18 inches (measured vertically) above the impactor’s position at rest.  A Category II rating (Class A per ANSI Z97.1) is given to glass when the impactor is dropped from a height of 48 inches.

At a minimum, all safety glass must comply with the criteria for Category II; however, Category I glass is permitted when the exposed surface area of a single pane is 9 sq. ft. or less, except for glazing around wet areas per Section 2406.4.5.  Glazing is permitted to be tested by ANSI Z97.1, but must comply with Class A, unless otherwise indicated in Table 2406.2(2) to be Class B.  All safety glazing must be identified by a permanent marking that indicates the manufacturer and the safety standard with which it complies, plus the information previously mentioned.

The IBC identifies seven specific hazardous locations where safety glazing is required:

1. Glazing in Doors:  Section 2406.4.1 requires that all glass in swinging, sliding, and folding doors, whether the glass is operable or fixed, must be safety glass (See Figure 3).  Safety glazing is not required if the glazed opening does not permit the passage of a 3-inch-diameter sphere.  Additionally, decorative glass⁴, curved glass panels in revolving doors, and glass in commercial refrigerated cabinets are also exempt from the safety glazing requirement.
2. Glazing Adjacent to Doors:  Section 2406.4.2 requires all glazing, fixed or operable, that is within a 24-inch radius of the vertical edges of the door (hinge and latch edges) in a closed position with a bottom exposed edge of glass that is less than 60 inches above the walking surface be safety glazing (See Figure 3).  Exceptions include decorative glass, where an intervening wall or permanent barrier is between the door and glazing (See Figure 4), where access through the door is to a closet 3 feet or less in depth, or in walls on the latch side and perpendicular to the door in one- and two-family dwellings and R-2 dwelling units.
3. Glazing in Windows:  Section 2406.4.3 requires glazing in windows, whether fixed or operable, to be safety glass when all of the following conditions exist:

• The exposed area of glass in a single pane is greater than 9 sq. ft.
• The bottom edge of the glass is less than 18 inches above the floor.
• The top edge of the glass is greater than 36 inches above the floor.
• A walking surface is located within 36 inches of the glass measured perpendicular to the glass surface.

Figure 3 - Safety glazing in doors and adjacent to doors

Figure 4 - Exception to requirement for safety glass when partition is between door and adjacent glass.

One exception to the requirements is decorative glass.  Another exception is when a horizontal rail is installed across the glass at a height of 34 to 38 inches.  The horizontal rail must withstand a horizontal load of 50 plf without contacting the glass and must be a minimum of 1½ inches in height (See Figure 5).  The last exception applies to insulating glass installed 25 feet above a walking surface, roof, grade, or other surface with a slope within 45 degrees of horizontal.  With this exception, the outboard pane is not required to be safety glass.

Figure 5 - Glazing in windows adjacent to walking surfaces with Exception 2 shown.

1. Glazing in Guards and Railings:  Section 2406.4.4 requires safety glass when glass is used as structural balusters or as infill panels within a railing system of a different material.  The requirement is applicable regardless of height above a walking surface.  Section 2407 has specific provisions for glass in guards and railings, which require tempered glass or laminated glass fabricated with either tempered or heat-strengthened⁵ glass.  Glass balusters must have an attached handrail or guard, unless the baluster is constructed of laminated glass of equal type and thickness, can withstand the loads for handrails and guards per Section 1607.8, and is approved by the building official.  Handrails and guards are required to be supported by a minimum of three glass panels, unless they are designed to be supported by other means.
2. Glazing in Wet Areas:  Section 2406.4.5 requires safety glass (for single pane and all panes of multi-glazed units) installed as fences, enclosures, or walls near swimming pools, hot tubs, spas, whirlpools, saunas, steam rooms, bathtubs, and showers when the bottom edge of the glass is within 60 inches vertically above any standing or walking surface.  The exception to this is that safety glass is not required if the glass is located more than 60 inches from the edge of the water when measured horizontally from the face of the glass (See Figure 6).
3. Glazing Adjacent to Stairs and Ramps:  Section 2406.4.6 requires safety glass when the bottom edge of the glass is less than 60 inches above the plane of the walking surface of stairs, landings between flights of stairs, and ramps.  Safety glass is not required if the stairway, landing, or ramp has a guard between the walking surface and the glass, and the glass is more than 18 inches horizontally from the guard.  The guard must comply with Section 1013 and shall withstand the loads per Section 1607.8.  Another exception to the safety glass requirement is if the glass is 36 inches or more, measured horizontally, from the walking surface.
4. Glazing Adjacent to the Bottom Stair Landing:  Section 2406.4.7 requires safety glass at the bottom stair landing when the bottom edge of the glass is less than 36 inches above the landing and within 60 inches of the last tread measured horizontally.  The only exception is one similar to that for stairs and ramps, when the glass is protected by a guard complying with Sections 1013 and 1607.8 and the glass is more than 18 inches from the guard.

Figure 6 - Criteria for safety glazing adjacent to wet areas.

Sloped Glazing and Skylights

Skylights and sloped glazing, because of their typical condition of being installed over occupied spaces, are subject to special limitations to protect occupants from falling glass.  Glazing is considered sloped when the angle at which it is installed is more than 15 degrees from vertical.

The types of glass permitted in skylights and sloped glazing include laminated glass with a 30-mil interlayer (polyvinyl butyral or equivalent), wired glass, light-transmitting plastics per Section 2607, heat-strengthened glass, or fully tempered glass.  If the glazing system consists of multiple layers, then each layer can be of any allowed material.

If heat-strengthened and fully tempered glass is used monolithically (i.e. not part of a multi-glazed unit) or as the bottom layer of a multi-glazed unit, then screens must be installed within 4 inches directly below the glass to catch the fragments should the glass break.  Section 2405.3 provides specific criteria for the screening.  Screening is not required as permitted by several exceptions:

• Fully tempered glass is permitted without screening if the glass is located between intervening floors and is sloped 30 degrees or less from vertical.  Additionally, the highest point of the glazing must be 10 feet or less above the walking surface.
• Screening is not required for, and annealed glass is permitted in, glazing where the walking surface is permanently protected from falling glass, or the area below the glass is not a walking surface.
• Screening is not required for, and annealed glass is permitted in, sloped glazing of commercial or detached noncombustible greenhouses used only for growing plants and which is not open to the public.  The height of the greenhouse ridge is limited to 30 feet.
• Fully tempered glass is permitted without screen in Groups R-2, R-3, and R-4, provided no pane is larger than 16 sq. ft., the highest point is no more than 12 feet above a walking surface or other accessible area, and the glass is 3/16 inch or less in thickness.
• Laminated glass with 15-mil interlayer (polyvinyl butyral or equivalent) is permitted without screening if used within dwelling units in Groups R-2, R-3, and R-4, provided no pane is larger than 16 sq. ft. and the highest point is no more than 12 feet above a walking surface or other accessible area.

Framing of sloped glazing and skylights in Type I and II construction must be noncombustible.  The IBC does permit the use of pressure-treated wood or other materials, when approved by the building official, if the environment within the building has a corrosive effect on metal framing.  The framing system must be capable of supporting the design loads required by Chapter 16.  Skylights must be set on a 4-inch curb if the slope of the skylight unit is at an angle of 45 degrees or less from the horizontal.  A curb is not required for Group R-3 if the slope of the roof is a minimum of 14 degrees (3:12 slope).

Glazing in Athletic Facilities

 Due to the higher potential for impact against glass in athletic facilities, the IBC has established requirements specific to those uses.  In racquetball and squash courts, glass shall be tested per CPSC 16 CFR Part 1201 or ANSI Z97.1 at a drop height of 48 inches.  However, the test method is modified to test an actual installation or an identical assembly, with all the required fixtures and fittings, and the impact point is located at a height of 59 inches above the playing surface.  To pass the test, the glass must remain intact following the impact, and the deflection at the point of impact cannot exceed 1½ inches.  In gymnasiums and basketball courts, the glazing must comply with CPSC 16 CFR Part 1201, Category II, or ANSI Z97.1, Class A.

What Happened to Wired Glass?

Not mentioned directly in the IBC, but addressed via compliance with current safety glazing standards, is the absence of traditional wired glass as safety glass.  For decades, wired glass was exempt from the impact requirements of CPSC 16 CFR Part 1201 if used in areas where fire-resistance and safety glass was required.  With the introduction of specialty fire-resistive glass that can comply with safety glazing standards, the federal standard and the IBC have removed the exceptions, and traditional wired glass is no longer permitted in areas where safety glass is required.⁶  Contrary to popular belief, traditional wired glass is not gone—it has always been permitted where annealed glass is allowed and in fire windows where safety glazing is not required.  However, wired glass that does comply with safety glass standards is now available, which typically includes an added film to improve its performance.

The use of glass in building construction will continue to grow as the benefits of daylighting are realized and integrated into building design.  Further, glass technology continues to improve allowing greater expanses of glazing with greater energy efficiency.  Glass is also being used in more creative applications, generating specialized areas in structural glazing systems.  Not addressed by the building code, but applicable based on circumstances, is the availability of security glass.  Although safety glass minimizes potential injury from accidental impact, it is not intended to prevent unwanted entry, stop the passage of a projectile fired from a weapon, or withstand the pressures created by an explosion.  Glass used in these applications is subject to additional testing based on standards that require a minimum performance that far exceeds those for safety glass.  Regardless of the varieties of glass types and performance levels that are available in the construction market, the basic requirement for safety still applies.

---

¹   Tempered glass is defined by GANA as “Flat or bent glass that has been heat-treated to a high surface and/or edge compression to meet the requirements of ASTM C 1048, Kind FT.”  “FT” means “fully tempered.”

²   Spandrel is defined by GANA as “panel(s) of a wall located between vision areas of windows, which conceal structural columns, floors and shear walls.”

³   For more information about wind-borne debris-resistant design, see “Glazing Design Beyond the Minimum” in the May 2012 issue of The Construction Specifier.

⁴   Decorative glass is defined in the IBC as a “carved, leaded or Dalle glass or glazing material whose purpose is decorative or artistic, not functional; whose coloring, texture or other design qualities or components cannot be removed without destroying the glazing material and whose surface, or assembly into which it is incorporated, is divided into segments.”  Dalle glass is made up of glass pieces “embedded in a cast matrix of concrete or epoxy.”

⁵   Heat-strengthened glass (Kind HS, per ASTM C 1048) is heat-treated glass similar to fully tempered, but at a compressive strength that is much lower than fully tempered.  Heat-strengthened glass is about two times stronger than annealed glass, but is not considered safety glass per CPSC 16 CFR Part 1201 or ANSI Z97.1.  Annealed glass is float glass that has been through a controlled cooling process.

⁶   See The Code Corner No. 5, “How You Can Change a Building Code,” for more information on the elimination of the wired glass exemption.

Elevators

One hundred and sixty years ago, Elisha Otis invented the first braking mechanism for the elevator, which made vertical travel within a building feasible and safe.  A little over forty years later, the gearless traction elevator was developed, which allowed movement in buildings of significant height.  Thus, along with the advent of inexpensive materials and advanced engineering and construction methods, the automatic elevator became a pivotal step that led to the surge of high-rise construction in the United States.  Since its introduction, the elevator has seen numerous advancements, but its purpose remains the same: moving people between floors of multi-story buildings efficiently and safely.

Like other systems within a building, elevators are regulated by the building code.  In the International Building Code (IBC)¹, Chapter 30 establishes the primary criteria for elevators, while other sections of the IBC supplement the primary criteria with special provisions, such as requirements for accessible means of egress, elevator lobbies, and shaft enclosures for hoistways.  In addition to the provisions in the IBC, elevators must also comply with the requirements in the American Society of Mechanical Engineers’ (ASME) A17.1, Safety Code for Elevators and Escalators², and ICC/ANSI A117.1, Accessible and Usable Buildings and Facilities³, which are referenced by the IBC.

General Elevator Planning and Design

With a couple of exceptions, neither the IBC nor ASME A17.1 dictate the number of elevators that must be provided in a building—any number of elevators may be provided at the discretion of the building owner.   The owner or architect may hire an elevator consultant to determine the elevator needs for buildings with high traffic or complex usage requirements.

As stated, there are a couple of exceptions in which the code regulates the number of elevator cars.  The first exception is in Section 1007.2.1, which requires at least one elevator be provided as one of the required accessible means of egress if an accessible story is located four or more stories above or below the level of exit discharge.  However, the elevator is not required if the building is sprinklered throughout per Section 903.3.1.1 (NFPA 13) or Section 903.3.1.2 (NFPA 13R), and includes either a ramp from the stories, or the stories incorporate a horizontal exit at or above the level of exit discharge.  The second exception is in Section 403.6, which requires at least two elevators be designated as fire service access elevators in buildings with occupied floors greater than 120 feet above the lowest level of fire department vehicle access.

If multiple elevators are provided in a building, the IBC requires that the number of cars within a single hoistway enclosure be limited to no more than four.  However, if four or more elevator cars serve all or the same stories, then the elevators must be located in a minimum of two hoistway enclosures.  Thus, if four elevator cars are provided, then they must be located in two hoistways in a 2-2 or 1-3 combination (See A and B in Figure 1).  If six elevator cars and two hoistways are provided, then the only combinations permitted would be 3-3 or 2-4 (See C and D in Figure 1)—a 1-5 combination would not be permitted, since no more than four cars are allowed in a single hoistway.

Figure 1 - Number of elevator cars in a hoistway.

Elevator car size is also regulated by the IBC and by ICC/ANSI A117.1.  In the IBC, if an elevator is provided in a building that has four or more stories above or below the grade plane, then at least one elevator shall be sized to accommodate an ambulance stretcher that is 24 inches wide by 84 inches long with corners having radii of 5 inches or more.  In ICC/ANSI A117.1, elevator cars shall have a clear dimension of 60 inches wide and 60 inches deep or 54 inches wide and 80 inches deep.  Elevator cars with centered doors may be 51 inches deep (54 inches to the doors) and 80 inches wide, provided the door has a 42-inch minimum width.  Additionally, elevator cars with 36-inch-wide side doors may be equally deep, but need only be 68 inches wide.  Existing elevators are exempt from the previous size criteria, provided elevators cars have clear dimensions of 36 inches wide and 54 inches deep, and have a clear floor area of 16 sq. ft.

Elevator hoistways penetrating more than three stories are required to provide venting at the top of the hoistways to allow heat and smoke to escape.  Except for Groups R-1, R-2, I-1, I-2, and other occupancies with sleeping units, venting is not required when the building is sprinklered throughout in accordance with NFPA 13 or 13R.  When venting is required, the vents must open directly to the exterior or through noncombustible ducts that terminate at the exterior.  The area of the vents shall be 3½% of the hoistway, but not less than 3 sq. ft. per elevator car.  Of the total required venting area, not less than ⅓ of the area must be permanently open with the remaining area closed off with annealed glass not greater than ⅛ inch thick.  Permanently opened venting is not required if automatic vents are installed that open when smoke is detected in the hoistway or in the elevator lobby (if lobbies are provided), upon power failure, or when activated by manual control. 

Other considerations that go into planning and design for elevators—also affected by the codes—are machine rooms, elevator lobbies, pits and clearances, and car finishes.  Machine rooms are regulated by both the IBC and ASME A17.1.  Requirements for elevator lobbies are only located in the IBC, while pits and clearances are only regulated by ASME A17.1.  Regarding elevator car finishes, the IBC is not very specific, but will likely consider elevators as enclosed spaces per Table 803.9.  On the other hand, ASME A17.1 provides specific criteria for car finishes and may supersede IBC criteria.

Pits and Clearances

ASME A17.1 separates criteria for pits and clearances in hoistways between electric and hydraulic elevators in Parts 2 and 3, respectively.  Typically, most of the requirements are in Part 2 and referenced by Part 3, except where specifically modified for hydraulic elevators.  For both types of elevators, the pit depth is based on the required equipment plus the minimum bottom car clearance of 24 inches when the elevator rests on fully compressed buffers or bumpers.  For top clearances, the requirements are basically the same, except the dimensions will likely vary between electric elevators (either counterweighted or uncounterweighted⁴) and hydraulic elevators.  Therefore, for design purposes, consult manufacturers’ design criteria for the types of elevators under consideration.

Machine Rooms

ASME A17.1 provides the majority of the technical requirements for machine rooms and spaces, but defers fire-resistive requirements to the building code.  The minimum clear headroom in a machine room per ASME A17.1 is 84 inches.  If fire resistance of the machine is not required by the building code, ASME A17.1 requires that machine rooms be constructed of noncombustible materials to a minimum height of 79 inches.  The IBC requires that machine rooms be of fire-resistive construction complying with the requirements for fire barriers, horizontal assemblies, or both.  The rating must be equal to the rating of the hoistway.  IBC Section 3002.1 requires that hoistways comply with Section 713 for shaft enclosures; therefore, if the shaft connects four or more stories, then the hoistway and the machine room must have a fire-resistance rating of 2 hours, or 1 hour if connecting fewer than four stories.  However, two exceptions are provided in the IBC:

• If a fire-resistance rating of 2 hours is required, then only a 1-hour rating is required if the machine room is not directly adjacent to the hoistway and no openings are provided between the hoistway and machine room.
• If the building is four stories or less and the machine room is not directly adjacent to the hoistway and no openings are provided between the hoistway and machine room, then the machine room is not required to have a fire-resistance rating.

The IBC simply states that machine rooms are to have an approved means of access; thus, the detailed criteria in ASME A17.1 will establish the minimum requirements for the means of access.  If the machine room is elevated above the floor or roof surface, then a permanent and noncombustible set of stairs or ladder, along with a landing at the top, is required to reach the machine room door.  The landing must be sized to allow the full swing of the door plus 24 inches if the door swings outward, or 29.5 inches if the door swings inward.  Although ASME A17.1 allows doors to machine rooms to have a width of 29.5 inches, the IBC requires a minimum clear width of 32 inches. 

If access to the machine room is across a roof, a stairway with a swing door shall be provided to the roof from the floor below—roof access hatches are not permitted.  If the roof slopes more than 15 degrees or the roof does not have a minimum 42-inch-high parapet or guardrail around the roof or passageway to the machine room, then a walkway must be provided.  The walkway must be 24 inches wide with railings 42 inches high consisting of a top rail, an intermediate rail or solid panel, and 4-inch-high toe-boards.

Elevator Lobbies

Elevator lobbies are required on each floor where an elevator shaft enclosure (i.e. hoistway) connects three or more stories.  The exceptions to the code do not require lobbies under the following conditions or locations:

• On the level of exit discharge if the level is sprinklered in accordance with NFPA 13.
• Elevators not required to be enclosed in a shaft per IBC Section 712.1.
• When hoistway openings are provided with additional doors that comply with smoke and draft control requirements of IBC Section 716.5.3.1 and tested per UL 1784, Air Leakage Tests of Door Assemblies, without a bottom seal.
• When the building is sprinklered throughout in accordance with NFPA 13 or 13R.  However, this exception is not permitted in Groups I-2 and I-3 and in high-rise buildings⁵.
• Elevator hoistways pressurized in accordance with IBC Section 909.21.
• Elevators only serving open parking garages.

When required or provided, elevator lobbies shall be enclosed with walls complying with the requirements for fire partitions.  Since elevator lobbies must have at least one means of egress, doors in elevator lobby enclosure walls shall comply with requirements for doors in corridors.  Ducts and air transfer openings in elevator lobby enclosures shall also be protected as required for corridors.  Elevator lobby enclosures may be constructed as smoke partitions per Section 710 in lieu of fire partitions, provided the building is sprinklered throughout in accordance with NFPA 13 or 13R.  If smoke partitions are provided, then doors need to comply with requirements for smoke and draft control.

Elevator lobbies are also required in the following special conditions and must comply with the requirements unique to each condition:

• Underground buildings where the elevator or elevators are shared by both smoke compartments⁶.
• Elevators designated as fire service access elevators.
• Elevators designated as occupant evacuation elevators.
• Elevator lobbies serving as areas of refuge.

Elevator Finishes and Materials

The IBC states that interior finishes for enclosed spaces must be of Class C or B materials, depending on whether the space is sprinklered or not.  However, that is not a decision that needs to be determined since ASME A17.1 requires finishes to be of Class B materials (a flame spread index less than or equal to 75 and a smoke developed index less than or equal to 450) when tested in accordance with ASTM E 84, Test Methods for Surface Burning Characteristics of Building Materials, or UL 723, Standard for Test for Surface Burning Characteristics of Building Materials.

If carpet or fabric (napped, tufted, woven, or looped) is used on elevator car walls, the material must be tested using the method specified in Section 8.3.7 of ASME A17.1.  The material shall not have a burn length greater than 8 inches, the flame shall extinguish within 15 seconds after removal of the flame source, and drippings shall not burn for more than 5 seconds.  Floor coverings, underlayments, and adhesives must have a critical radiant flux of not less than 0.45 W/cm² when tested in accordance with ASTM E 648, Standard Test Method for Critical Radiant Flux of Floor-Covering Systems Using a Radiant Heat Energy Source.  Handrails are permitted, but not required, inside elevator cars.

Glazing is permitted in elevator cars and hoistways per IBC Section 2409 and ASME A17.1.  When installed in elevator hoistways, glass shall be laminated safety glazing complying with 16 CFR 1201 Category II or ANSI Z97.1 Class A.  If the hoistway is required to be fire-resistance rated, then the glazing must also comply with IBC Section 716 for opening protectives.  Since Section 716 is referenced, glazing tested in accordance with ASTM E 119, Test Methods for Fire Tests of Building Construction and Materials, or UL 263, Standard for Fire Tests of Building Construction and Materials, may be used in lieu of complying with the limitations of Section 716. 

In hoistway doors, glass shall comply with the same criteria for hoistways, except that ASME A17.1 permits wire glass in vision panels without reference to any safety glazing standards; however, the IBC will permit wire glass provided that the glass complies with the safety glazing standards previously mentioned.  With the exception of vision panels, glazing in hoistway doors must not be less than 60% of the total visible door surface area; likewise, car doors must have the same minimum area for glass as viewed from the car side.  There is no requirement that glass, if provided, must be used in both the car and hoistway doors, nor is it required that the areas of glazing in each be equal.

When glass is installed as part of the elevator car enclosure, ASME A17.1 requires laminated safety glazing complying with 16 CFR 1201 and that it be mounted so that the assembly will pass the elevator tests without damage.  Additionally, ASME A17.1 requires that a handrail or other framing be provided if the glass panels are wider than 12 inches.  The IBC further requires that glass used within an elevator, either as a wall lining or as part of the enclosure, comply with 16 CFR 1201 Category II or ANSI Z97.1 Class A.  Since ANSI Z97.1 is not referenced by ASME A17.1, then, to comply with both codes, only materials complying with 16 CFR 1201 Category II should be used. 

Both the IBC and ASME A17.1 allow tempered glass when used as a lining for elevator car walls.  If used, tempered glass must be bonded to a coating, sheeting, or film backing to hold fragments in place if broken.  The tempered glass cannot be sandblasted, etched, heat treated, painted, or have received any other treatment that would affect the characteristics of the glass.  Finally, the IBC requires that tempered glass comply with 16 CFR 1201 Category II or ANSI Z97.1 Class A, which is more specific than the safety glazing requirements specified by ASME A17.1.

Elevators as Accessible Means of Egress

Elevators required or provided as an accessible means of egress must comply with requirements in IBC Section 1007.4.  To be considered an accessible means of egress, elevators must be provided with standby power in accordance with NFPA 110, Emergency and Standby Power Systems, or NFPA 111, Stored Electrical Energy Emergency and Standby Power Systems.  NFPA 110 provides requirements for generators, whereas NFPA 111 provides requirements for stored energy type systems, such as batteries.

As previously mentioned, elevator lobbies may serve as a required area of refuge for elevators used as an accessible means of egress.  Elevators are not required to be accessed by an area of refuge when buildings are sprinklered throughout with a system complying with NFPA 13 or 13R, when elevators are not required to be enclosed in a shaft, and when elevators are accessed by a horizontal exit.  If used as an area of refuge, elevator lobbies must be enclosed with smoke barriers and provided with two-way communication to the fire command center or other location approved by the fire department.  Also, elevator lobbies used as areas of refuge must accommodate one 30- by 48-inch wheelchair space for every 200 occupants served by the area of refuge.  The wheelchair spaces cannot reduce the required means of egress width.

Fire Service Access and Occupant Evacuation Elevators

Fire service access and occupant evacuation elevators were introduced in the 2009 IBC and modified in the 2012 IBC.  As mentioned earlier, buildings with an occupied floor more than 120 feet above the lowest level of fire department vehicle access must provide two elevators designated as fire service access elevators.  Passenger elevators in high-rises are permitted to be used as occupant evacuation elevators.  Additionally, in high-rise buildings greater than 420 feet in height, elevators complying with the requirements for occupant evacuation may be used in lieu of the required third stairway.

Fire service access elevators were added to the IBC in Section 3007 as a result of research conducted following the World Trade Center tragedy of September 11, 2001.  According to the code change proposal, these requirements were recommended to “provide a reasonable degree of safety for firefighters” when “staging firefighters and equipment one or two floors below the fire.”  Elevators used for fire service access are required to be identified by a pictorial symbol representing a firefighter’s helmet that shall be mounted on the face of hoistway door frame that is perpendicular to the hoistway door.

Fire service access elevators must have access to a fire service access elevator lobby on each floor, except at the level of exit discharge.  Each lobby shall have direct access to an interior exit stairway, which shall be provided with a Class I standpipe.  If a fire service access elevator has two entrances to a floor, the second entrance is permitted to have access to a standard elevator lobby as described earlier.  Fire service access elevator lobbies must be enclosed with smoke barriers.  Doorways to a fire service access lobby shall be fire door assemblies having a ¾-hour rating and complying with smoke and draft control requirements of Section 716.5.3.1.  The size of a fire service access elevator lobby must be a minimum 150 sq. ft. in floor area with no dimension less than 8 feet.

Other unique criteria apply to fire service access elevators.  For example, sprinklers are not permitted in machine rooms, machine spaces, and hoistways of fire service access elevators, and water from sprinklers outside the fire service access elevator shall be prevented by approved means from entering the fire service access elevator hoistway.  Fire service access elevators and associated equipment shall be supplied by normal and standby power.  Wires and cables from outside the fire service access elevator that provide power, communications, fire detection, and control signals for the elevator must be protected by construction having a fire-resistance rating of not less than 2 hours.

Occupant evacuation elevators were added to the IBC in Section 3008 to provide occupant self-evacuation.  Prior to the introduction of occupant evacuation elevators in the 2009 IBC, elevators were not permitted to be used by building occupants for means of egress.  These provisions are voluntary, but, if provided, all public passenger elevators must comply with the provisions.  For the most part, occupant evacuation elevators must comply with the same requirements for fire service access elevators in regard to the fire sprinkler prohibition, prevention of outside sprinkler water from entering the hoistway, and protection of wires and cables. 

Elevator lobbies serving occupant evacuation elevator have requirements identical to fire service access elevator lobbies, such as smoke barrier enclosure construction (except at level of exit discharge), doorways, and access to an interior exit stairway; however, occupant evacuation elevator lobbies have additional provisions.  Doors, in addition to the fire-resistive requirements, must also have vision panels consisting of fire-protection-rated glazing and be automatic closing by fire alarm signal if kept open by magnetic or other hold-open devices.  The size of the occupant evacuation elevator lobby shall be a minimum of 3 sq. ft. per occupant based on not less than 25% of the floor occupant load served by the lobby.  Furthermore, a 30- by 48-inch wheelchair space is required for every 50 occupants of the occupant load of the floor area served by the lobby.  The lobby shall also be provided with two-way communication identical to that required for areas of refuge.

Occupant evacuation elevators shall be identified as such on all floors with an approved sign located adjacent to each call station.  Lobbies serving occupant evacuation elevators must provide a status indicator that shows by green illumination that elevators are available for occupant evacuation when elevators are in normal service and the fire alarm system has indicated an alarm.  If the elevators have been switched to emergency recall service by the fire department, the status indicator should show by red illumination that elevators are not available for evacuation and that stairs should be used.  At all other times, no illumination or message should be indicated.

Structural Integrity for High-Rise Elevator Hoistways

If high-rise buildings are classified as Risk Category III or IV⁷ in accordance with Section 1604.5, or if the building has a height greater than 420 feet, then elevator hoistway enclosures must comply with the requirements for structural integrity per Section 403.2.3.  These provisions were introduced in the 2009 IBC as a result of recommendations developed following the World Trade Center tragedy.  The intent is to provide increased resistance to structural damage from external impacts.

The wall assembly surrounding a hoistway must comply with Soft Body Impact Classification Level 2 as determined by ASTM C 1629/C 1629M, Standard Classification for Abuse-Resistant Nondecorated Interior Gypsum Panel Products and Fiber-Reinforced Cement Panels, which requires the entire assembly to withstand an impact of a 195 pound force.  The exterior face of the hoistway (the wall surface not facing the stairway) must consist of either two layers of material complying with Hard Body Impact Classification Level 2, or one layer of material complying with Hard Body Impact Classification Level 3.  Additionally, any materials that, when combined and tested together, comply with Hard Body Impact Level 3 shall be permitted.  Concrete and masonry construction are deemed to comply with the requirements for the Soft Body and Hard Body Classification requirements and are not required to be tested.

------------------

This article does not attempt to address all the requirements relating to elevators.  Most of the requirements associated with elevators—essentially those in ASME A17.1—pertain to the fabrication of elevators and associated equipment and accessories, of which elevator manufacturers are acutely aware.  Specifications for elevators in the construction documents should require compliance with ASME A17.1 and with ICC/ANSI A117.1, the 2010 ADA Standards, or both.  Since elevators vary among manufacturers, design professionals should consult manufacturer representatives when designing and specifying elevators, especially if custom designs are proposed for elevator cars, entrances, call stations, and hall signals.

---

¹   References to the IBC are for the 2012 edition unless indicated otherwise.

²   The 2007 edition of ASME A17.1 is referenced by the 2012 IBC.

³   The 2009 edition of ICC/ANSI A117.1 is referenced by the 2012 IBC.  The elevator requirements in the 2009 ICC/ANSI A117.1 is virtually identical to the 2010 ADA Standards, which were adopted by the Department of Justice to replace the ADA Accessibility Guidelines (ADAAG).

⁴   Counterweighted elevators use ropes with weights to help offset the weight of the elevator car for ease in moving the car.  Uncounterweighted elevators are identified by ASME A17.1 as screw column elevators and rack-and-pinion elevators that do not require counterweights.

⁵     High-rise buildings are defined as buildings with an occupied floor located more than 75 feet above the lowest level of fire department vehicle access.

⁶     Underground buildings as buildings with an occupied floor more than 30 feet below the lowest level of exit discharge.  Requirements for underground buildings are located in Section 405 of the IBC.  Underground buildings with floors more than 60 feet below the level of exit discharge must be divided into two smoke compartments, each with access to an elevator unless the elevator or elevators are shared by both compartments.

⁷     Risk Category III buildings are those “that represent a substantial hazard to human life in the event of failure,” and Risk Category IV buildings are those “designated as essential facilities.”  Refer to Table 1604.5 for specific uses identified for each category.

Openings - Part 2

 

In Part 1, the importance of protecting openings was addressed with a focus on interior windows and doors.  But opening protection is not limited to interior construction; openings in exterior walls are also subject to protection. 

Openings in Exterior Walls

Protection requirements for openings located in exterior walls are determined in a manner completely different than that for interior openings.  One of the most notable differences is that just because an exterior wall is required to be of fire-resistive construction does not mean that openings in that same wall are required to be protected.

Fire-resistive requirements for exterior walls are determined in Chapter 6 of the International Building Code (IBC)¹.  Table 601 sets the fire-resistive construction for exterior bearing and nonbearing walls based on construction type.  For nonbearing walls, Table 601 references Table 602, which determines the fire-resistance rating based on three factors: fire separation distance, type of construction, and occupancy group.  The fire-resistance rating for exterior bearing walls will vary from 1 hour for Type VB construction to 3 hours for Type IA construction, but according to footnote “f” of Table 601, the fire-resistance rating cannot be less than that required by Table 602.  Therefore, if Table 601 indicates that the rating for the exterior bearing wall is 1 hour and Table 602 requires the same wall to be 2 hours, Table 602 governs, and the wall must be of 2-hour fire-resistive construction. 

That explains the requirements for exterior walls, but establishes no criteria for openings.  To determine the fire-resistive requirements for openings, Section 705 must be consulted.  Unlike interior fire-resistance-rated assemblies, where all openings are required to be protected based on the fire-resistance rating of the wall assembly, openings in exterior walls may be unprotected, protected, or a combination of both.  The allowable area of each is determined by the percentages indicated in Table 705.8, based on fire separation distance and sprinkler protection; however, the sprinkler protection only impacts allowable area of unprotected openings.

The percentages provided in Table 705.8 are the maximum areas permitted for openings per story.  For example, if a fire-resistance-rated exterior wall is located 12 feet from the lot line, and the building is two stories in height, then 45% of the wall area of each story is permitted to have protected openings, or unprotected openings if the building is sprinklered throughout; or, if the building is not sprinklered throughout, then 15% of the wall area at each story is permitted to have unprotected openings. 

To better explain how Table 705.8 is applied, consider the building elevation in Figure 1.  Each story is 10 feet in height; the parapet cannot be included in the second story exterior wall area since the IBC definition of “story” is the measurement from the floor to the next floor or roof above, so the measurement must be to the roof line and not to the top of the wall.  Therefore, the area of wall for each story is 750 ft.².  For this example, the building is nonsprinklered and the wall has a fire separation distance of 18 feet. 

To determine if the openings in this building elevation require protection or not, the first step is to determine the actual area of openings per floor.  The first story has a total opening area of 366 ft.² (81 ft.² × 4) + 42 ft.²; the second story has 105 ft.² of openings (21 ft.² × 5).

 
Figure 1 - Building Elevation.

The next step is to determine the percentage of openings per story.  The percentage of openings in the first floor wall area is 49% (366 ft.² ÷ 750 ft.²).  The second story has 14% of its wall area as openings (105 ft.² ÷ 750 ft.²).  With these percentages, we can determine whether or not the openings require protection.

As previously mentioned, the fire separation distance for the wall is 18 feet.  Looking at Table 705.8, each story is permitted to have protected openings in 75% of the wall area or 25% unprotected openings, since the building is nonsprinklered.  The percentage of actual openings at the second floor is 14%, which is less than 25%; therefore, all the windows in this story may be unprotected.  However, the first story has openings which cover 49% of the wall, which exceeds the allowable 25%, but does not exceed the 75% allowable area for protected openings.  Thus, the first floor must have protected opening.

If unprotected openings are desired, then the building must be sprinklered, since 75% of the wall area is permitted to have unprotected openings if the building is sprinklered throughout.  But if sprinklering the building is not an option, and the project cannot afford the cost of protected openings, then there are only two alternatives available:  1) reduce the area of openings so that the percentage is equal to or less than the allowable area for unprotected openings, or 2) provide a mix of protected and unprotected openings to reduce the area of protected openings required.  The first one is easy, but may not achieve the desired result.  The second one requires some manipulation to achieve compliance.

Therefore, in the example, the door will be considered unprotected and the storefront glazing is protected.  If a combination of protected and unprotected openings are used, then the sum of the ratios of actual to allowable areas cannot exceed 1, which is provided by Equation 7-2 in the IBC:  (A_p/a_p)+(A_u/a_u) ≤ 1, where A_p is actual area of protected openings, a_p is allowable area of protected openings, A_u is actual area of unprotected openings, and a_u is allowable are of unprotected openings.  The allowable area for protected openings (a_p) would be 75% of the wall area for the story, or 562.5 ft.², and the allowable area for unprotected openings (a_u) would be 25% or, 187.5 ft.².  Since the actual area of the door is 42 ft.² (A_u) and the actual area of the storefront glazing is 324 ft.² (A_p), the equation would be set up as follows:

(A_p/a_p) + (A_u/a_u) = (324 ft.²/562.5 ft.²) + (42 ft.²/187.5 ft.²) = 0.576 + 0.224 = 0.8 ≤ 1

The discussion thus far has only mentioned openings as either protected or unprotected, with no mention of the requirements for a protected opening in the discussion of fire-resistance ratings.  For openings in exterior walls, the fire-resistance ratings are provided in Table 715.4.  For walls with a 1-hour fire-resistance rating, openings are required to have a ¾-hour or greater rating.  For exterior walls with a 2- or 3-hour fire-resistance rating, the openings must have a 1½-hour or greater rating.  If our example building is of Type VA construction with a Group B occupancy, and the wall is nonbearing, then the fire-resistance rating of the wall would be 1-hour per Tables 601 and 602.  Therefore, the openings in the wall would need to have a ¾-hour rating.

Walls Not Parallel With Lot Lines

Determining protected openings is easy when the exterior walls are parallel with the lot line; however, not all buildings are constructed square with their lots nor are all lot shapes rectilinear.  So when a building has an exterior wall that is not parallel with the adjacent lot line, the determination of protected openings gets a little more complicated.  The easy approach is to use the fire separation distance between the exterior wall and the lot line at the closest point and apply that percentage to the entire length of the exterior wall.  However, that can be a somewhat overly restrictive.

Even though the IBC does not address nonparallel exterior walls and lot lines, the following method uses the IBC principles of exterior wall opening protection in a segmental application over the entire length of the wall (See Figure 2). 

 Figure 2 - Opening protection for angled lot lines. (P) Protected; (UP,S) Unprotected, Sprinklered; (UP, NS) Unprotected, Nonsprinklered.

The method requires establishing lines parallel to the wall in question at distances equal to the ranges used in Table 705.8.  The reason the lines are parallel to the wall is that fire separation distance is measured perpendicular to the wall and not the lot line per IBC definition.  At the point where each distance line intersects the lot line, establish another line perpendicular to the distance line back to the building’s wall.  These lines create the zones of fire separation distance along the length of the exterior wall.

For each zone, determine the length and identify the permitted allowable opening percentage.  The percentage is then applicable to each zone based on the area for that zone (length of zone × story height).  Using the example in Figure 2, if the building had a story height of 13 feet and it was nonsprinklered, the permitted unprotected opening areas would be as follows:

• Zone A:  No openings permitted
• Zone B:  15.6 ft.² (12 ft. × 13 ft. × 10%)
• Zone C:  23.4 ft.² (12 ft. × 13 ft. × 15%)
• Zone D:  39 ft. ² (12 ft. × 13 ft. × 25%)
• Zone E:  40.95 ft.² (7 ft. × 13 ft. × 45%)

The same process is used for each zone for protected openings, or for unprotected openings if a sprinkler system is installed throughout.  For a combination of protected and unprotected openings, the same process described earlier for mixed openings is used, but is applied to each zone separately.

Exterior Opening Exceptions

There are several exceptions to the requirements for openings in exterior walls.  In Section 705.8.1 there are two exceptions.  The first exception applies to openings in the first story for all occupancy groups except Group H and has two conditions, of which only one or the other needs to be met.  The first condition allows unlimited unprotected openings when the exterior wall faces a street and has a fire separation distance greater than 15 feet.  The second condition allows unlimited unprotected openings when the exterior wall faces an occupied space that is at least 30 ft. wide and is accessed by a street using a fire lane.  This condition may seem odd, since Table 705.8 allows unlimited unprotected openings when the fire separation distance is 30 ft. or greater.  However, this condition permits the open space to be one that is not on the building’s lot, as long as the space is dedicated for public use or is an open space between buildings on the same lot².

The second exception to Section 705.8.1 allows unlimited unprotected openings when the exterior bearing and nonbearing walls, as well as the exterior primary structural frame, are not required to be fire-resistance rated.  Therefore, this exception would only apply to Types VB, IIIB, and IIB; and if a sprinkler system is used to substitute for 1-hour construction, the exception would also apply to Types VA, IIIA, and IIA.

Although not technically considered exceptions, the footnotes of Table 705.8 also provide some alternatives to the general requirements for exterior wall opening protection.  Footnote “d” allows 25% of the wall area to have protected and unprotected openings in a Group R-3 building when the fire separation distance is 3 feet to less than 5 feet; footnote “e” does not permit openings for Groups H-2 and H-3 when the fire separation distance is less than 15 feet; footnote “f” allows unlimited protected and unprotected openings for Group R-3 when the fire separation distance is 5 feet or greater; and the area of openings in an open parking structure is not limited when the fire separation distance is 10 feet or greater.

Vertical Separation of Openings

Openings in exterior walls may need to be vertically separated in accordance with Section 705.8.5. If openings in adjacent stories are within 5 feet of each other (See Figure 3) and the window in the story below is unprotected, then the openings must be separated by a 3-foot, 1-hour fire-resistant-rated spandrel or a 30-inch, 1-hour fire-resistant-rated horizontal flame barrier (See Figure 4).  As always, there are exceptions to the requirements.

 
Figure 3 - Horizontal distance that requires compliance with vertical separation requirements.

 
Figure 4 - Vertical separation of openings in exterior walls.  (A) Provides separation by use of vertical, fire-resistance-rated spandrel.  (B) Provides separation by use of horizontal, fire-resistance-rated flame barrier

The exceptions exclude buildings under certain conditions from complying with the vertical separation requirements.  The first exception is for buildings that have three or fewer stories above grade plane.  The second applies to any building that is sprinklered throughout with either an NFPA 13 or NFPA 13R system.  The final exception applies to all open parking garages.

Alternate Methods for Determining Fire Ratings of Openings

As mentioned in Part 1 of this article, one of the standards for fire-resistance-rated doors is NFPA 252.  For fire-resistance-rated windows, the acceptable standards include NFPA 257 and UL 9.  For alternative methods of determining fire-resistance ratings of openings, the IBC identifies four methods or procedures in Section 715.3.  However, whichever method or procedure is selected, it must be based on one of those three standards.

The four methods and procedures listed in the IBC include 1) designs documented in approved sources, 2) calculations performed in an approved manner, 3) engineering analysis based on comparison to openings with a fire rating determined by one of the three standards, and 4) alternative methods allowed by Section 104.11.  The first method allows selecting openings that have been tested and listed in various sources such as UL and FM Global.  The second requires using a calculated method that has been approved by the building official; this may require consulting a specialist, which is also likely for the third method.  The fourth method allows the use of the alternative materials, design and methods section of the IBC, which may require a research report, testing, or both.

Windows that are not Openings

Even though this two-part article series is titled “Openings,” it would not be complete without a discussion on windows that are not considered openings, but are in fact considered fire-resistance-rated walls.  Section 715.2 states that glazing tested in accordance with ASTM E 119, Test Methods for Fire Tests of Building Construction and Materials, or UL 263, Standard for Fire Test of Building Construction and Materials, are not subject to the requirements of Section 715 for opening protectives. 

A few manufacturers provide products that have been tested using these two standards and are thus not openings, but more like “fire-rated transparent walls,” since they have been tested using the same standards as required for fire-resistance-rated wall assemblies, such as fire walls and fire barriers.  Although not currently addressed in the IBC, glazing that has been tested and has passed the requirements of ASTM E 119 or UL 263, including the prevention of radiant heat, are given the “W” mark for “Walls” in lieu of the “D” and “OH” marks mentioned in Part 1 of this article³.  Therefore, they can be included in exterior and interior locations where fire-resistance-rated assemblies are required and not be limited to the size and area restrictions for openings.  Fire-rated transparent walls may have unlimited area as long as each lite of glazing, bounded by the frame, does not exceed the maximum tested area.

Another difference between glazed openings and fire-rated transparent walls is the required fire-resistance rating.  As mentioned earlier in this article series, the fire-resistance ratings for openings are, in most cases, lower than the fire-resistance rating of the walls in which the openings are installed.  However, fire-rated transparent walls, when installed in place of typical fire-resistance-rated wall assemblies, must have a fire-rating that is equal to or greater than the required rating for the wall assembly.  For example, if the required rating for a fire barrier used as an occupancy separation is 2-hours, then the rating for the fire-rated transparent wall must also be 2 hours or greater.

While many fire-rated glazing systems are manufactured using ceramic, wired, or specialty tempered glass, fire-rated transparent walls utilize tempered glazing that is laminated with an intumescent interlayer.  When a fire reaches a temperature to shatter the tempered glass on the fire side, the intumescent layer will create a char that will insulate the opposite side from radiant heat transfer.

There are a couple of things to keep in mind when considering the use of fire-rated transparent walls.  The first thing to consider is the cost; fire-rated transparent walls are not inexpensive.  The second is possible resistance from the local building department to accept these systems as anything but openings.  This resistance is usually derived from the misconception that “if you can see through it, then it’s an opening.”  Even though this perception is contrary to the IBC, building departments are made up of people, and it may take some effort on the part of the design team to convince the local building department that these systems are in compliance with the code.

Coordination with Other Requirements

The placement of openings in fire-resistive assemblies must be carefully considered to ensure that maximum allowable areas are not exceeded; but coordination with other sections of the IBC is just as important.  Fire-resistance-rated doors must also conform to the means of egress requirements of Chapter 10, and fire-resistance-rated windows need to comply with the safety glazing requirements of Chapter 24 when located in one or more of the hazardous locations listed.  Additionally, exterior fire-resistance-rated openings are subject to the structural load requirements of Chapters 16 and 24, as well as the energy requirements of the International Energy Conservation Code, if adopted.

Protected openings are essential in order to make buildings functional when fire-resistive construction is required by the building code.  Otherwise, to move from one fire area⁴ to the next would require exiting and reentering the building.  Just installing a door or window in these assemblies is not enough; the fire-resistive performance of the wall assembly must not be significantly compromised.  Therefore, opening protection is required to maintain that minimum fire-resistive performance.

---

¹   References to the IBC in this article are for the 2009 Edition.

²   Typically, fire separation distance between buildings on the same lot is measured between the face of the wall and an imaginary line between the buildings.

³   The “W” mark has been approved for the 2012 Edition of the IBC.

⁴   A “fire area” is defined in the IBC, in part, as “The aggregate floor area enclosed and bounded by fire walls, fire barriers, exterior walls or horizontal assemblies of a building.”

Openings - Part 1

 

“The act or an instance of becoming open or being made to open.”  “An open space serving as a passage or gap.”  “An unfilled job or position; a vacancy.”  “A breach or aperture.”¹

The word “opening” has many meanings, as indicated above.  However, with its many specific code-related definitions, it is surprising that the International Building Code (IBC)² does not provide its own definition of “opening.”  So, in the absence of a code-specific definition, the latter definition from the above list is very apt when referring to doors, windows, and other “breaches” in fire-resistance-rated assemblies. 

Fire-resistance-rated assemblies (i.e. fire walls, fire barriers, fire partitions, smoke barriers, and horizontal assemblies) have been tested to restrict the spread of fire; but openings, such as doors and windows, located in these assemblies, introduce points of weakness.  Therefore, openings in a fire-resistance-rated assembly must afford some protection to maintain a minimum level of fire resistance throughout the extent of the assembly.  The IBC establishes requirements for openings in Chapter 7 in three locations.  The first location is Section 705.8 for openings in exterior walls; the second location is Section 712.8 for floor doors in horizontal assemblies; and finally, the third location is Section 715, which is titled “Opening Protectives”—the primary location for opening requirements.

Standards for Openings

In order for an opening to be used in a fire-resistance-rated assembly, the opening must be tested in accordance with the standards indicated in the IBC based on type of opening.  The IBC defines three types of openings:  the fire door assembly, the fire window assembly, and the floor fire door assembly, which is used only in the horizontal position.  The use of the word “assembly” with each of these terms indicates that it includes all components necessary for a complete opening, such as frames, hardware, glazing, and other accessories.

For side-hinged and pivoted swinging doors, the applicable test standards are National Fire Protection Agency’s (NFPA) 252, Standard Methods of Fire Tests of Door Assemblies, or Underwriters Laboratories (UL) 10C, Positive Pressure Fire Tests of Door Assemblies.  Other doors are required to be tested in accordance with either NFPA 252 or UL 10B, Fire Tests of Door Assemblies. 

The positive pressure requirement for fire door assemblies was introduced in the 1997 Uniform Building Code after much debate and has remained a requirement in the IBC.  It was expected that the hose stream requirement for fire doors would be eliminated from test standards if positive pressure was incorporated, but the hose stream test (discussed in the next paragraph) has remained in U.S. fire door test standards.  UL 10C integrates the positive pressure requirements into the test standard; however, NFPA 252 does not, so the IBC requires that the neutral pressure plane be moved to 40 in. or less above the sill after 5 minutes into the test.  The positive pressure requirement provides a more realistic condition experienced by fire door assemblies during an actual fire event (See Figure 1).

The hose stream portions of the UL 10C and NFPA 252 tests are not indicative of an assembly’s ability to withstand firefighting operations, but to test the structural durability of the assembly through thermal shock from the cool water and the impact and scouring effect of the water blast against the assembly.  Fire door assemblies in walls of corridors and smoke barriers are not required to pass the hose stream test of either standard.

  

Figure 1 - Positive Pressure Requirement

An exception to the tests above are those doors that have been tested in accordance with UL 10A, UL 14B, and UL 14C.  The doors applicable to these standards are tin-clad fire doors usually constructed of a wood core with sheet metal applied to faces and edges.  Historically, tin-clad doors were often associated with old warehouses, and may be of the swinging, horizontally sliding, or vertically sliding types.  Even so, some manufacturers continue today to fabricate doors of this type. 

Another exception to the door testing requirements is for floor fire door assemblies.  Doors of this type are required to be tested in accordance with NFPA 288, Standard Methods of Fire Tests of Floor Fire Door Assemblies Installed Horizontally in Fire Resistance-Rated Floor Systems.  Where openings are needed in a fire-resistance-rated horizontal assembly, the floor fire door can be a solution.  Floor doors are subject to fire exposure that is different from that experienced by standard vertical fire doors, such as the lack of differential pressure along the plane of the door surface and exposure to higher temperatures from the rising heat.

For fire window assemblies, the required tests are either NFPA 257, Standard on Fire Tests for Window and Glass Block Assemblies, or UL 9, Fire Tests of Window Assemblies.  The only exceptions to these standards are wired glass and glazing complying with the requirements of ASTM E 119, Standard Test Methods for Fire Tests of Building Construction and Materials, or UL 263, Fire Tests of Building Construction and Materials.  The latter exception will be addressed in detail in Part 2 of this article.  Like fire door assemblies, fire window assemblies are also required to be tested under positive pressure, but only within 10 minutes of test start and at a height that leaves two-thirds of the window above the neutral plane.

Fire Door Assemblies

The required fire protection rating of a fire door assembly is based upon both the rating and the type of fire-resistive assembly in which the fire door assembly is located.  Like fire-resistive assemblies, the fire protection ratings for fire door assemblies are also given in hours.  Fire protection ratings are provided in Table 715.4 of the IBC. 

Fire door assemblies, at a minimum, must be provided with a label complying with the requirements of NFPA 80, Standard for Fire Doors and Other Opening Protectives, and shall bear the name of the manufacturer or the manufacturer’s traceable identification number, the name or trademark of the third party inspection agency, and the fire protection rating (See Figure 2).  Frames for fire door assemblies are also required to have a label, but it is not required that the fire protection rating be included.

In addition to controlling the spread of fire, fire door assemblies must also control drafts and the passage of smoke.  To measure a fire door assembly’s performance in these areas, the assembly shall be tested in accordance with UL 1784, Air Leakage Tests of Door Assemblies.  New in the 2009 edition of the IBC is the basic acceptable performance level with which fire door assemblies must comply.  Doors complying with the smoke and draft control requirements shall be identified with an “S” on the required label.

 
Figure 2 - Fire Door Label Example

If a door that requires a fire protection rating is larger than the fire door assembly that was tested, then the required label mentioned earlier will need to indicate the door is oversized. Another option is to have an approved testing agency provide a certificate of inspection attesting to the fact that the door is constructed in the same manner as the tested fire door assembly.

Fire door assemblies located in exit enclosures and exit passageways are required to minimize the transmission of heat from the exposed side through the door to the unexposed side, thus reducing the amount of radiant heat occupants may experience while egressing through the exits.  The IBC requires that the temperature rise on the unexposed surface of the fire door assembly cannot exceed 450°F above the ambient temperature at the end of a 30 minute period.  Fire door assemblies that are required to comply with this requirement must have that shown on the required labels (See Figure 2).  Further, if glazing in the fire door assembly exceeds 100 in.², then the glazing must also pass the temperature rise criteria.  Buildings that are equipped throughout with an automatic sprinkler system in accordance with either NFPA 13 or NFPA 13R are not required to comply with either temperature rise provision.

For obvious reasons, the IBC precludes the use of louvers in fire doors.  However, UL provides listings for fire door louvers used in fire doors with fire protection ratings up to 1½-hour.  The UL requires that such louvers be tested in accordance with UL 10B or UL 10C—the same tests to which fire door assemblies are subjected.  With regard to the specific prohibition in the IBC, designers should obtain approval from the building official before incorporating a UL-listed louver into a fire door assembly.

In fire walls, the area of fire door assembly openings is limited to 156 ft.² unless the buildings on each side of the fire wall are sprinklered throughout in accordance with NFPA 13—NFPA 13R systems are not allowed that exception.  Additionally, the aggregate width of openings on any floor level cannot exceed 25% of the overall length of the fire wall.

Glazing in fire door assemblies is permitted, but some restrictions do apply.  According to NFPA 80, glazing is permitted when tested as part of the fire door assembly.  The IBC indicates that glazing shall have a fire protection rating equal to the rating required for the fire door assembly.  The size of glazing in a fire door assembly is limited by NFPA 80 and the IBC.  NFPA 80 limits the area of glazing to that tested as part of the fire door assembly.  However, ¾-hour doors are limited to a maximum area of 1296 in.² with a maximum dimension not exceeding 54 in.  Additionally, in 3-hour doors, NFPA 80 limits the glazed area to a maximum of 100 in.².  The IBC further restricts glazing to 100 in.² in 1½-hour fire door assemblies that are installed in fire barriers.

Glazing used in fire door assemblies shall be permanently labeled with a four-part identification code.  The first part of the identification code is the letter “D,” which indicates that the glazing is suitable for a fire door application and has been tested in accordance with NFPA 252.  The second part is either an “H” or “NH,” which indicates that the glazing has passed or not passed, respectively, the hose stream requirements of NFPA 252.  The third part is either a “T” or “NT,” which indicates the glazing complies or does not comply, respectively, with the temperature rise requirements of the IBC.  And finally, the fourth part is the fire protection rating in minutes.  Thus, an identification code such as “D—H—NT—120” translates into glazing suitable for a 2-hour fire door that has passed the hose stream test, but has not passed, or was not tested for, the temperature rise requirement.

Glazing utilized in fire door assemblies must also comply with the safety glazing requirements of the IBC.  Chapter 24 of the IBC requires that glazing in doors comply with the requirements for Category I glazing as established by test in accordance with the Consumer Product Safety Commission (CPSC) 16 CFR 1201, Safety Standard for Architectural Glazing Material.  Category I safety glazing will withstand a 100 pound weight swung from a pendulum at a distance of 18 in. from the glass surface.  If the area of glazing exceeds 9 ft.², then the glazing must comply with Category II requirements, which increases the distance of the weight in the test to 48 in. from the glass surface.

A discussion on fire door assemblies would not be complete without addressing door hardware.  A fire door assembly is required to have a latch that will secure the door when closed, preventing passage of smoke and fire into the unexposed side.  But a latch would be useless if the fire door assembly is allowed to remain open, therefore IBC Section 715.4.8 requires that fire door assemblies be provided with closers that are either automatic- or self-closing, unless they are installed in walls separating sleeping units in Group R-1 occupancies.

Generally, “self-closing” requires the use of standard door closers that will close and latch the door when released.  “Automatic-closing” usually includes devices such as magnetic door holders that release doors when triggered by an alarm situation.  However, Section 715.4.8.2 states that automatic-closing fire door assemblies “shall be self-closing in accordance with NFPA 80.”  Therefore, the language of the IBC seems to limit all fire door assemblies to the “self-closing” type, even though NFPA 80 permits the use of “automatic-closing” fire door assemblies. 

But Section 715.4.8.3 identifies where smoke-activated, automatic-closing fire door assemblies may be installed.  These locations include doors across corridors; doors in smoke barriers, fire walls, fire partitions, and shaft enclosures; as well as in other locations.  The actuation of the closer is limited to a 10-second delay after being triggered by a smoke detector or loss of power to the smoke detector or hold-open device.  Overhead sliding or rolling fire door assemblies are permitted to be actuated by either heat- sensitive devices, such as a heat detector or fusible link, or smoke detectors connected to the building alarm system.

Transoms and sidelights that are a part of the frame for a fire door assembly are permitted provided the fire protection rating of the assembly is ¾-hour or less.  For fire door assemblies exceeding a ¾-hour rating, transoms and sidelights must comply with either ASTM E 119 or UL 263.  Glazed units that are not part of a fire door assembly shall comply with requirements for fire window assemblies.

Fire Window Assemblies

The required fire protection ratings of fire window assemblies are provided in IBC Table 715.5 and are based on the type and rating of fire-resistive assembly in which the windows are installed.  For interior construction, fire windows are limited to fire-resistive assemblies that have ratings of 1 hour or less.  Therefore, all fire walls and fire barriers with ratings of 2 hours or more are not permitted to have fire window assemblies.  In all cases where fire window assemblies are permitted, the area of a fire window assembly cannot exceed 25% of the common wall area in any room (See Figure 3).

Figure 3 -  Common Wall Area Determination

The size of a single pane of glazing in a fire window assembly is limited to 1296 in.² with no dimension exceeding 54 in. unless tested to a larger size, dimension, or both.

Wired glass assemblies are one of the exceptions to the testing requirements for fire window assemblies.  Wired glass that is ¼-inch thick set in steel frames having a metal thickness not less than 0.125 in. are considered to meet the requirements for a ¾-hour fire window assembly.  The maximum area of wired glass permitted under this exception is an absolute 1296 in.² with no dimension exceeding 54 in.  Wired glass assemblies that have been tested in accordance with the standards for fire window assemblies are permitted to have larger glazed areas and dimensions if tested at those larger sizes.

Like glazing in fire door assemblies, glazing in fire window assemblies are also required to be of safety glazing if located in areas identified in Chapter 24.  The only exception is that glazing in fire window assemblies may be tested in accordance with the recently updated ANSI Z97.1, Safety Glazing Materials Used in Buildings—Safety Performance Specifications and Methods of Test, in lieu of the CPSC 16 CFR 1201 standard.

Fire-protection-rated glazing used in fire window assemblies must also be permanently marked with a label or other identification that provides the name of the manufacturer, the test standard, and a two-part identification code. The first part of the identification code is “OH,” which indicates that the glazing is suitable for an opening and has passed the hose stream test.  The second part of the identification code is the fire protection rating in minutes.  Therefore, fire-protection-rated glazing with the identification code “OH—45” indicates the ¾-hour glazing is suitable for openings and has passed the hose stream test.

Installation

Fire door and fire window assemblies are required to be installed in accordance with NFPA 80.  Doors required for smoke and draft control must be installed in accordance with NFPA 105, Standard for the installation of Smoke Door Assemblies.  NFPA 80 limits the clearance at the bottom of a fire door to a maximum of ¾ in.  above the floor and the clearance between the top and vertical edges of the door and door frame is ⅛ in. (± 1/16 in.)  for steel doors and a maximum 1/8 in. for wood doors.

Openings—Part 2

Part 2 of this article will address openings in exterior walls, including calculating allowable area of protected and unprotected openings based on fire separation distance.  Also included will be information on alternate methods used to determine fire protection ratings of openings.  Part 2 will wrap up with a brief discussion on when a window is not considered an opening.

---

¹ The American Heritage Dictionary of the English Language, Fourth Edition, 2000, Houghton Mifflin Company.

² References to the IBC in this article are for the 2009 Edition.

Click Here to download a PDF version of this article.