Glazing Industry Code Committee

Q: If the roof height of a residential solarium is more than 12 feet above the floor, when is laminated glass required?
A: The International Residential Code, 2006 Edition (IRC), Section R308.6.2, permits specific types of glazing to be used in skylights and sloped ceilings. Laminated glass is one of the types of glass permitted. If the highest point of the glass is more than 12 feet above the floor, the minimum interlayer thickness shall be 0.030 inches. The other permitted materials (fully tempered glass, heat-strengthened glass, wired glass, and approved rigid plastics) may also be used with certain limitations.

Q2: Is there a minimum fire protection rating for glazing in the door leaf of doors?
A: Glazing installed in the door leaf of fire doors is required to have a fire protection rating that matches the rating of the door. Fire door ratings range from 20-minutes to 3 hours.

Q3: Do overhead garage doors require safety glazing?
A: The Federal Safety Standard, CPSC 16 CFR 1201 does not apply to garage doors designed for vehicular passage, but glazing material in doors of garages designed solely for human passage is included within the scope of CPSC 16 CFR 1201 and therefore, must satisfy the standard’s safety criteria. Glass in a sectional garage door does not require safety glazing.

Q2: Are there model code requirements on glass in escalator handrails?
A: Yes, section 2407 of the International Building Code (IBC), 2006 Edition, states that glass in railings shall be either monolithic fully tempered glass, laminated fully tempered glass or laminated heat-strengthened glass. The minimum nominal thickness shall be ¼” and the glass is to comply with the safety glazing Category II requirements of CPSC 16 CFR 1201.

Q2: When glazing forms an enclosure for a whirlpool in a single-family dwelling, what are the requirements?
A: Glazing in doors and enclosures for whirlpools shall comply with CPSC 16 CFR 1201 Category II. If the glazing is in the wall that forms the enclosure and it is less than 60 inches above the standing surface it shall comply with CPSC 16 CFR 1201 Category II or ANSI Z97.1-2004 Class A.

Q2: What is the difference between a fire door and a fire door assembly, and related areas where fire-rated glazing may be required?
A: The 2007 Edition of the National Fire Protection Association (NFPA) 80 – Standard for Fire Doors and Other Opening Protectives provides the following definitions:

Q3: Does the International Building Code (IBC), require a hose stream test for fire-rated glazing?
A: Yes, with the exception of glass lites installed in the door leaf of doors required to have a fire protection rating of 20 minutes or less.

Q4: What is required for glazing to meet Category II of CPSC 16 CFR 1201 for an athletic facility?
A: To meet CPSC 16 CFR 1201 Category II (or ANSI Z97.1-2004 Class A), it must not break at all or break safely when impacted at 400 ft-lbs force from a 100 lb lead shot filled bag. The impact performance is satisfactory if the glass breaks and the impact creates small enough particles of glass for tempered lites and no penetration large enough for a 3” solid sphere placed on the opening for laminated to pass through freely. There may be additional requirements on structural and glazing technique for an athletic facility in the building code.

Q5: What are restrictions associated with the use of wired glass?
A: In the past, model building codes have provided an exception for wired glass installed in locations requiring fire-rated glass. However, the 2006 Edition of the International Building Code (IBC) no longer contains the exception. If wired glass is installed in a hazardous location, it must meet the applicable safety glazing requirements. If the wired glass is installed in a location that is not a hazardous location, the wired glass need only meet the applicable fire protection requirements.

Q2: Is decorative glazing in doors required to be safety glazing?
A: Glazing in doors is addressed by CPSC 16 CFR 1201 which contains a limited exception from the safety glazing requirements meeting the criteria in Section 1201(c)(4). For other applications, the International Building Code (IBC) also contains an exception for decorative glass (see Section 2406.3.1, IBC 2006).

Q2: What are restrictions associated with the use of wired-glass?
A: In the past, model building codes have provided an exception for wired glass installed in locations requiring fire protection rated glass. However, the 2006 Edition of the International Building Code (IBC) no longer contains the exception. If wired glass is installed in a hazardous location, it must meet the applicable safety glazing requirements. If the wired glass is installed in a location that is not a hazardous location, the wired glass need only meet the applicable fire protection requirements.

ASHRAE 90.1 is the energy standard most often used for commercial buildings and for residential buildings over three stories. The IECC includes different chapters for low-rise residential buildings (three stories or less) and commercial buildings (including high-rise residential buildings). The IRC includes requirements for low-rise one and two-family homes and townhouses. The IECC and IRC have very similar requirements up through the 2006 version, and both are widely used for low-rise one and two family homes and townhouses.

A few jurisdictions have their own energy codes which differ from ASHRAE 90.1, IECC, and IRC, most notably California, Florida, Oregon, and Washington.

Each model energy code has prescriptive requirements for the U-factor, Solar Heat Gain Coefficient (SHGC), and air leakage of fenestration products, based upon climate zone, building type, and product type. ASHRAE 90.1, IECC, and IRC all use the same 8 climate zones as shown below:

Q2: Where is low-e glass required?
A: Basically everywhere, or at least where the most recent energy code has been adopted and is enforced. The exact prescriptive requirements vary depending on which version of ASHRAE 90.1, IECC, or IRC is being enforced in a particular location. For the latest versions (ASHRAE 90.1-2007, 2006 IECC, and 2006 IRC), low-e is essentially required in all climate zones. In the north, the low U-factor necessitates the use of low-e, as well as good frames, and possibly argon gas fill. In the south, the low Solar Heat Gain Coefficient (SHGC) requires glazing with a tint, reflective coating, or spectrally selective low-e coating. Because of the recent increased demand for high light transmittance and daylighting, this has meant the increased use of low-e.

Q3: Where is double glazing required?
A: With the latest versions of the model energy codes, double glazing is required everywhere except zone 1 (just the southern tip of Florida, Hawaii, Puerto Rico, and the Virgin Islands). The exact prescriptive requirements vary depending on which version of ASHRAE 90.1, IECC, or IRC is being enforced in a particular location. For the latest versions (ASHRAE 90.1-2007, 2006 IECC, and 2006 IRC), the prescriptive U-factor requires double glazing in all climate zones except zone 1. However, single glazing may still be used if an alternate trade-off method is used (refer to Q5 for information on trade-off methods).

Q4: Are the code requirements for center-of-glazing or whole product? What’s the difference?
A: All U-factor, Solar Heat Gain Coefficient (SHGC), and Visible Transmittance (VT) requirements in ASHRAE 90.1, IECC, and IRC are whole product values, meaning that the effect of the frame is included along with the glazing. Because the frame is opaque, the whole product VT will always be lower than the center-of-glazing value. For U-factor and SHGC, the difference depends upon the relative amount of glazing vs. frame area, as well as the different glazing and frame materials. In general, center-of-glazing values are not accepted for code compliance. The one exception is that ASHRAE 90.1 allows the center-of-glazing SHGC as an alternative for complying with the whole product SHGC (refer to Q7 for more information on exceptions).

Q5: Are there options besides the basic prescriptive requirements for U-factor and SHGC?
A: Yes. All model energy codes generally have three different ways to comply. The first is simply to meet the prescribed U-factor and SHGC values for your climate zone and application. The second is a simplified trade-off where lower performance in one envelope component can be offset by higher performance in another – for example, area-weighting across different window types, or trading off a higher glazing U-factor for increased wall insulation. The third is a complete building performance simulation where any change in the building is allowed as long as the overall proposed building has the same or lower energy cost as a hypothetical reference building meeting the prescriptive requirements. This third option is the most complex, but also allows the most flexibility, with the ability to trade-off performance between different building components, HVAC equipment, etc.

Q6: What are the rating and labeling requirements for glazing in the energy codes?
A: It depends. There are no labeling requirements if the glazing either uses conservative, worst-case default values for U-Factor and SHGC, or falls under certain exemptions. More information about default values and exemptions is provided in Q7 below.

Otherwise, the IECC, IRC, and ASHRAE 90.1 all require that the U-factor and SHGC be determined by an accredited, independent laboratory in accordance with NFRC technical procedures (NFRC 100 and 200). However, although the manufacturer or glazing contractor must follow NFRC technical procedures and use an accredited independent laboratory, only a few places such as California and Washington require use of the full NFRC certification program including registration with NFRC, additional review by an Independent Certification and Inspection Agency (IA), and fee payment.

For commercial glazing, some manufacturers also rate their products using AAMA 507, which is an alternative rating standard still based on NFRC technical procedures but more suited to the custom nature of the commercial glazing industry. Not all jurisdictions accept this alternative rating system. Although an actual individual label is common for residential windows, certificates listing installed products on a building are more common than labels for commercial projects.

Q7: What exceptions are there to rating, labeling, and meeting the U-factor and SHGC requirements?
A: First, even if a product does not fall under one of the following exceptions, each model code allows the use of default U-factor and SHGC values for unlabeled products. The exact value depends on the code, the framing type, and the glazing type. However, in each case, the default values are designed to be conservative, worst-case values, and often will not meet the prescriptive requirements. Therefore, default values are usually only used when an alternative trade-off method is being used (refer to Q5 for more information on trade-off methods).

Several exemptions or exceptions to U-factor and SHGC requirements are listed below:

Q8: What is a projection factor, and how does that affect glazing code compliance?
A: The projection factor (PF) is a measure used to describe how well an overhang shades glazing, and is important when determining code compliance with SHGC requirements. Projection factor is calculated as the furthest horizontal distance out away from the glazing surface, divided by the distance from the bottom of the glazing to the bottom of the overhang. For example, a 2 ft overhang offset 1 ft above a 5 ft high window would have a PF = 2 / (5+1) = 0.33.

For commercial glazing, both ASHRAE 90.1 and IECC give credit towards meeting the SHGC requirement for using overhangs. In the IECC, higher SHGC values are allowed based on projection factors less than 0.25, between 0.25 and 0.50, and higher than 0.50. In ASHRAE 90.1, the SHGC used for compliance is determined by reducing the actual product SHGC by a multiplier based on the projection factor and the direction the glazing faces. ASHRAE 90.1 also includes a procedure for calculating the effectiveness of partially opaque overhangs (e.g. using translucent materials, perforated materials, or louvers). The effective SHGC is reduced more for larger overhangs, and for more opaque materials.