1) What is the correct amount of light for the space I am designing?

2) Are all Low Emissivity (Low-E) coatings the same?

3) The industry offers Low-E coatings on the #2 surface and on the #3 surface of an
insulating glass unit. On which surface should the coating be located to achieve optimal
solar performance?

4) When choosing a silk-screen pattern, how important is the role of the ceramic frit color?

5) How do I specify hurricane-resistant glass?

6) How do I specify blast mitigating glass?

7) Does Viracon supply glass products that are bullet resistant?

8) What is the Condensation Resistance Factor of a given glass make-up?

9) When designing an insulating unit with a laminated component, where should the laminate be positioned, closer to the exterior/outside elements or towards the building interior?

10) When is safety glazing required?

11) Can I butt-glaze an insulating glass unit that spans from the floor to the ceiling?

12) Does Viracon supply glass for transparent floor applications?

13) Does Viracon offer a switchable-Privacy Glass product?

14) Does Viracon offer fire-rated glass?

15) Does Viracon offer x-ray glass?


Q: What is the correct amount of light for the space I am designing?

A: Design your space based on its intended usage and occupancy comfort. Atriums, for example, in which people are mainly passing through, can be designed with high levels of light. Office areas where people are working with computers monitors require lower levels of light to provide more contrast with display screens.

In addition, the angle of the sun and space elevation in relation to the sun must be considered along with the space usage. For example, a coffee and pastry shop with a western elevation could provide occupancy comfort while allowing in high levels of light transmittance based on a high traffic levels in the morning hours. If this same business is on an eastern elevation, the level of light transmittance should be reduced to accommodate the morning sun and provide occupancy comfort.

A common range of light transmittance for glazing where personnel are working on computer monitors is 30% - 50%. A common range for an atrium area could be 60%- 75%.

Q: Are all Low Emissivity (Low-E) coatings the same?

A: There are two methods used to manufacture low-e glass, pyrolytic deposition and vacuum deposition. The difference between the two is the pyrolytic deposition method applies the coating to molten glass during the manufacturing process. Vacuum deposition, on the other hand, applies the coating to finished glass in a large vacuum chamber.

Specific to vacuum deposition, expanded flexibility exists to apply the low-e coating to a variety of tinted glass substrates. Frequently the combination of a low-e coating and tinted glass require heat-treating due to increased thermal stresses associated with such combinations and should be reviewed during the design stage. Post heat-treatable low-e coatings are offered in the market today that allow fabrication and heat-treatment after the vacuum deposition of the coating.

In general, a greater offering of low-e coatings in combination with colored glass options are available with the vacuum deposition process conducted after heat-treating is complete.

Important to note: All coated glass of the same general color and visible light transmittance may not be alike in U-value, shading coefficient, visible reflectance and other solar optical properties. A comparison of values should be reviewed in relation to the mechanical specifications for the building.

Q: The industry offers Low-E coatings on the #2 surface and on the #3 surface of an insulating glass unit. On which surface should the coating be located to achieve optimal solar performance?

A: According to the Glass Association of North America 2004 Glazing Manual, "A low-e coating on the second (#2) surface of an insulating glass unit is more effective at reducing solar heat gain, especially when used in conjunction with tinted glass. The low-e coating will reflect re-radiated heat (IR), while the tinted glass reduces the solar radiation through the glass, resulting in less glare and heat gain."

Product evaluations conducted by Viracon have revealed that surface 3 orientations of a low-e coating can act as a heat trap for commercial buildings, increasing the room-side glass temperature by as much as 13æF.

Q: When choosing a silk-screen pattern, how important is the role of the ceramic frit color?

A: The ceramic frit color plays a contributing role to a silk-screen pattern's level of reflectivity, boldness or subtleness, and solar performance.

In all cases, incorporating a silk-screen pattern to a glass make-up will increase the solar performance of the product vs. the same make-up without a silk-screen. A white ceramic frit is often used in applications desiring to create a bold pattern, that stand out more than a tinted ceramic frit, along with maintaining high levels of light. If the desire is to minimize the glass reflectance, then a tinted ceramic frit may be more appropriate offering a more subtle pattern while improving solar performance.

Q: How do I specify hurricane-resistant glass?

A: It is important to note that glass is only a component of the overall configuration that equates to a hurricane-resistant window system. Many other components contribute to the performance of the glazing such as; frame, silicone, anchorage, hardware, etc. Thus, the complete glazing system must meet the specified hurricane test protocol to be considered a certified hurricane-resistant product. Viracon offers glass laminates specifically designed to meet this criterion when installed into a suitable glazing system. (For more information on these laminated glass types refer to the Protective Glass section of this website.)

When specifying glass to meet a building code requirement of hurricane resistance, choosing the Viracon laminated glass product that is most suitable will depend upon what was tested in the certified framing system that has been selected. For example, if the framing system type is pre-determined (i.e. Kawneer, Efco, YKK, Vistawall, etc.) then the hurricane resistant glass laminate required would equal that tested in the certified hurricane-resistant system design. However, in the more likely case that this can not be determined at the design phase, Viracon recommends a sample specification to include a list of suitable laminated glass products for large and small missile requirements. It is then important to note in the specification that these laminates must be used in combination with a certified glazing system designed to meet the specified hurricane test protocol.

Please contact a Viracon Architectural Design Associate at 800-533-2080 for assistance with writing a specification for these glass products.

Q: How do I specify blast mitigating glass?

A: Since glass is only a component of the overall configuration that equates to a blast resistant window system, many other components contribute to the glazing performance such as: frame, silicone, anchorage, hardware, wall structure, etc. Viracon offers several laminated glass products to meet this criterion when installed into a suitable glazing system.

The first step in evaluating which laminate will be required is to determine what level of threat the building owner is trying to protect against. Typically, this is determined through a risk assessment of that building. From a glazing standpoint, several key factors need to be considered:

- Blast Load
- Acceptable Injury Hazard Level
- Glass Size and Amount of Glass
- Framing Design
- Additional Requirements, such as; Solar Control and Aesthetics

For more information on blast-mitigating glass refer to the Protective Glass section of this website.

Q: Does Viracon supply glass products that are bullet resistant?

A: Yes, Viracon supplies a wide range of glass-clad polycarbonate laminates that are bullet resistant and have been certified to the U.L. 752 criterion. Note that the correct term is stated as "resistant"and not "proof", as the purpose is to provide resistance from a bullet penetrating through the glass product. These laminates are typically supplied for exterior glazing of commercial and government buildings where severe threats are high.

For more information on Viracon glass-clad polycarbonate laminates, called GuardVueTM refer to the ballistic and forced entry product information under the Protective Glass section of this website.

Q: What is the Condensation Resistance Factor of a given glass make-up?

A: Condensation resistance factor or CRF is determined from a guarded hot box test as specified in AAMA 1503.1. Thermocouples are used in prescribed locations on the glass and the average glass temperature is then used to determine the CRF. Since CRF is dependent upon such factors as glass size and the framing system type, the actual value must be determined by test. Based on previous mock-up testing, however, we estimate that a 1"VE1-2M insulating vision glass would have a CRF of 55 to 60. Argon-filling would increase this value to 60 - 65.

Q: When designing an insulating unit with a laminated component, where should the laminate be positioned, closer to the exterior/outside elements or towards the building interior?

A:Viracon recommends that the laminate be supplied to the interior or inboard of the insulating glass unit. Since the laminate is the protection piece and most often the intent is to protect potential victims on the interior of the space, the laminate should be closest to the victim side.

In addition, typically when designing with an insulating unit often a high performance coating will be incorporated for enhanced thermal performance. The fact that sputter coatings perform best on the #2 surface of an insulating unit vs. when encapsulated within a laminate, the exterior ply is recommended to be monolithic with the high performance coating on the #2 surface to achieve maximum thermal performance.

Q: When is safety glazing required?

A: First of all, what is safety glazing? Safety glazing meets the federal safety standard Consumer Product Safety Commission (CPSC) 16 CFR Part 1201 Safety Standard for Architectural Glazing Materials. Examples of safety glazing are fully tempered glass and a 7/32"laminated glass with a .030 PVB interlayer qualify as safety glazing materials.

Safety glazing is required in all doors including storm doors and combinations doors. This includes bathtub doors and enclosures, shower doors and enclosures and sliding glass doors. In addition, any glazing next to a door or an opening for human passage is considered a "sidelite" and requires safety glazing if the nearest exposed edge is:

- Within 24 horizontal inches of the vertical edge of the door in a closed position and
- Where the bottom exposed edge is less then 60 inches above the walking surface.

Any glazing in an area not considered a door or sidelite requires safety glazing if all of the following conditions are met:

- The lowest edge of the glass is less than 18 vertical inches above a walking surface and
- The top edge of the glass is greater then 36" above the floor and
- There is a walking surface within 36 horizontal inches of such glazing; and
- The glazed panel is greater than 9 square feet.

The Consumer Products Safety Commission establishes the standards for safety glazing. Hazardous locations that require safety glazing are designated by the Model Building Codes. Because each state has either adopted the model building code, modified it in some sections, or written completely new sections it is imperative to be guided by the particular state or local building code where the glass is to be installed. For detailed information contact your local code officials.

Q: Can I butt-glaze an insulating glass unit that spans from the floor to the ceiling?

A: For clarification purposes, a true butt-glazed application is defined as the installation of glass products where the vertical glass edges are without structural supporting mullions.

In general, insulating glass units should not be used for butt-glazed (or unsupported edge) applications. In order to prevent premature insulating glass seal failure, Viracon requires that the edges of insulating glass be supported so that edge deflection does not exceed the span divided by 175 (L/175).

For more information or additional questions related to this topic please contact a Viracon Technical Services Representative at 800-533-2080.

Q: Does Viracon supply glass for transparent floor applications?

A: Viracon does not offer glass for floor applications. Our focus is supplying glass solutions for exterior glazing of commercial buildings.

Q: Does Viracon offer a switchable-Privacy Glass product?

A: Viracon no longer offers this type of glass product.

For reference, we can provide a couple alternative sources that offer a similar technology. Please note these companies are not affiliated with Viracon nor our product offering.

Polytronix
805 Alpha Drive
Richardson, TX 75081
Tel: 972-238-7045
www.polytronix.com

Laminated Technologies
2900 Dusa Drive
Melbourne, FL 32935
Tel: 321-751-1130
www.laminatedtechnologies.com

Q: Does Viracon offer fire-rated glass?

A: Currently, Viracon has fire-rated glass products that are 20-minute and 45-minute rated, although these products are typically used for applications that also require some level of impact protection as they consist of a polycarbonate inner core. Viracon continues to evaluate more glass product options to expand this product line in the future.

Q: Does Viracon offer x-ray glass?

A: No, Viracon does not supply glass used for x-ray purposes. Our product line consists of glass products suitable for commercial glazing applications.