--- title: Facts About Glass | Vitro Glass Education Center description: These FAQs are full of facts about glass to help you specify the right building products for your projects. --- [![Vitro Architectural Glass](https://www.vitroglazings.com/assets/images/vitro_logo_color.svg)](https://www.vitroglazings.com/) - [Products](https://www.vitroglazings.com/products/) - - [Low-e Glass](https://www.vitroglazings.com/products/low-e-glass/) - [*Solarban*® 60 Glass](https://www.vitroglazings.com/products/low-e-glass/solarban-60-glass/) - [*Solarban*® 60 *Optiblue*® Glass](https://www.vitroglazings.com/products/low-e-glass/solarban-60-optiblue-glass/) - [*Solarban*® 65 Glass](https://www.vitroglazings.com/products/low-e-glass/solarban-65-glass/) - [*Solarban*® 70 Glass](https://www.vitroglazings.com/products/low-e-glass/solarban-70-glass/) - [*Solarban*® 70 *Optiblue*® Glass](https://www.vitroglazings.com/products/low-e-glass/solarban-70-optiblue-glass/) - [*Solarban*® 72 Glass](https://www.vitroglazings.com/products/low-e-glass/solarban-72-glass/) - 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Any heat source, such as furnaces or engines, which consume and combust fossil fuels, release long wave energy. Objects such as a sidewalk, road or windowsill which have been exposed to short wave solar radiation will also emit long wave infrared energy. Therefore, the sun is not responsible for long-wave infrared energy, instead it provides short-wave solar radiation. How is glass made? Almost all glass produced today in developed countries is done so by the “float process.” The glass composition materials, mainly silica sand, soda ash and limestone, are melted in a furnace and then flowed on to a bath of molten tin. The glass is formed and gradually cools as it moves from the tin bath to an annealing lehr, which is a controlled cooling chamber. As it moves through this process, the glass is in the form of a continuous ribbon, which is cut to size and packaged at the final stage. [![Click to Watch](https://glassed.vitroglazings.com/hubfs/Video/EDU/thumbnails/How_Glass_is_Made_1_thumb.png)](https://glassed.vitroglazings.com/faqs#inline-content) ![How\_Glass\_is\_Made\_1](https://play.vidyard.com/YHZRzqHvmri52PoFYGCAPx.jpg) How is threat factor measured? Material Threat Factor, often called simply threat factor, was developed by the American Bird Conservatory (ABC). The ABC defines threat factor as “a way to assign scores that provide a relative measure of how well materials with patterns of visual markers cause avoidance by birds in a standard, controlled test environment.” Tunnel tests, in which birds are flown down a dark tunnel toward glass samples with and without deterrent designs, are used to determine the threat factor of glass. What are building-integrated photovoltaics? Building-integrated photovoltaic (BIPV) modules consist of solar cells that are laminated between two glass lites. BIPV modules can complement classic building materials such as facades, sunshading and balustrades, or even replace them. What are the most common types of glass? All float glass, as it is initially made in the above description, is called annealed and is the most common. Float glass is made in a variety of colors or tints, in addition to basic clear glass. With annealed glass, the starting point can be further fabricated in many ways. Coatings of various types can be applied to achieve many visual effects and affect the optical properties. In addition, the glass can be heat-treated to increase its strength and give it safety glazing properties. Glass can be put into an insulating glass unit, meaning two or more pieces of glass are separated by a dry air space to improve the insulating properties. What are the Shading Coefficient and the Solar Heat Gain Coefficient? These terms are mathematically related and both describe the solar energy blocked from passing through a glass material. The shading coefficient is the ratio of solar energy that passes through a piece of glass relative to piece of 1/8” clear glass (which has a shading coefficient of 1.0). Solar heat gain coefficient represents the solar gain through the glass relative to the incident solar radiation; it is equal to 86% of the shading coefficient. In either case, a lower number indicates improved solar control over the 1/8” clear glass baseline. What is a curtainwall? Curtainwall refers to the exterior covering of a building that is assembled from non-structural components, typically glass and/or aluminum. Curtainwall systems are generally more energy-efficient and long-lasting than traditional glass storefronts. What is a solar panel? A solar panel uses photovoltaic (PV) cells applied to glass lites, also known as front sheets, to capture solar energy and convert it into renewable electricity. What is bird glass? Bird-safe or bird-friendly glass typically is characterized by visual markers applied in a pattern etched onto the glass. These markers help birds identify glass surfaces and avoid collisions, which is a known safety issue. What is better, a high or low shading coefficient? In colder, heating-dominated climates such as Canada or the northern United States, windows with higher shading coefficients generally are preferred and conserve energy due to the fact that in the longer heating season, more solar radiation, which becomes “free” heat, is allowed to pass into a home. In the south, with a long air-conditioning season, it is most important to reduce solar gain and therefore reduce air conditioning loads. What is the best glass product for the sunbelt areas of the country? Proper window design in the south must account for solar heat gain in order to help reduce air-conditioning. Therefore, glass products should have a low solar heat gain coefficient or low shading coefficient; the u-value, or insulating performance is of lesser importance. What is the difference between long wave and short wave infrared? - Short wave infrared energy comes directly from the sun, but is not felt as heat. It converts into heat when it strikes something. - A hot automobile dashboard or a hot sidewalk or roadway where you can often see heat radiating from the surface is an example of long wave infrared. What is the difference between U-value and R-value? U-value is used to measure the performance of assemblies such as IGUs, while R-value is used to measure the performance of most other parts of the building envelope, such as walls, floors and roofs. U-value and R-value are mathematical reciprocals of each other; while lower U-values indicate better insulating performance, higher R-values indicate better thermal resistance. What is the highest performing IGU you can assemble? Currently, Vitro’s *VacuMax*™ Vacuum Insulating Glass paired with *Solarban*® 70 glass offers a U-value of 0.05, which is a 79% percent improvement over an IGU that uses *Solarban*® 70 glass alone, and provides an R-value up to R20, which represents a 380% improvement in thermal performance.  What is vacuum insulating glass? Vacuum insulating glass consists of two glass lites separated by a seal and a vacuum space. This configuration effectively blocks thermal transmission, delivering thermal insulation performance that is superior to both conventional insulating glass and monolithic glass.   ### Safety Glass FAQs What is safety glazing? Glass is a breakable material, which when broken into smaller sharp pieces often called shards can cause serious injury. Safety glazing material, usually tempered glass or laminated glass, reduces the risk of injury. In the case of tempered glass, this is accomplished by the characteristic break pattern (many small pieces), and in the case of laminated glass, the adhesion of the glass pieces to the inner plastic layer. What is security glazing? Security glazing products usually involve multiple layers of glass, and in some cases acrylics (usually laminated) in order to achieve maximum impact resistance from explosions, ballistic assaults and even simple forced entry. There is a wide range of such specialty glass products. What are the U.S. standards for testing safety glazing materials? ANSI Z97.1 and CPSC 16CFR, Part 1201. Where should safety glazing be used? The Federal safety glazing law stipulates that safety glazing be used in architectural applications (homes and buildings) in defined hazardous locations. The hazardous locations generally include doors, immediately adjacent sidelites, bath and shower enclosures and glazing adjacent to passages where there are walking surfaces adjacent to the glass and the bottom edge of the glass is within 18” of the floor. In addition to the Federal law, various local code authorities have additional requirements. Are there special safety glazing requirements in overhead glazing? Many local building codes mandate special considerations for overhead glazing. It is common to require and use tempered glass in residential overhead applications. Laminated, often heat-treated glass, is commonly required in commercial building applications. Typically when tempered glass is allowed in commercial building, some form of restraining screening is also required below the glass. How is safety glazing marked for identification? The Federal safety glazing law requires that all safety glazing products have a permanently identifiable marking on each piece. This marking cannot be removed without damaging or breaking the glass and is generally located in one of the corners of each piece.   ### Low-e Glass FAQs Can you use low-e glass by Vitro Architectural Glass (formerly PPG glass) in a single-glazed window? *Sungate*® 400 coated glass and *Solarban*® 60, *Solarban*® 67, *Solarban*®70XL, *Solarban*® 72, *Solarban*® Z50, and *Solarban*® R100 coated glasses must be used only as a component of a sealed insulating glass unit. In addition, all low-e coated glasses yield their best energy performing characteristics when used in sealed, insulating glass units. Is it better to have the coating on the #2 or #3 surface of an insulating glass unit? The answer to this question is really dependent on the specific design conditions of your application. The light transmittance and the U-value of the unit will be the same whether the coating is on the #2 or #3 surface. However, the Solar Heat Gain Coefficient will be lower when the coating is on the #2 surface. In general, if you are concerned about reducing solar heat gain (typically in a cooling climate), then using the coating on the #2 surface would best meet the requirement. On the other hand, if you are interested in utilizing passive solar heat gain (typically in a heating climate), then using the coating on the #3 surface would best meet the requirement. What are the differences between low-e coated glass products by Vitro Glass? Vitro Architectural Glass (formerly PPG glass) manufactures a variety of low-e coated glasses using two different manufacturing processes. The following table identifies the Vitro glass product and associated manufacturing process. | Vitro Low-E Coated Glass Products | | | --- | --- | | **Product** | **Manufacturing Process** | | *Sungate*® 400 Coated Glass | MSVD | | *Solarban*® Z50 Coated Glass | MSVD | | *Solarban*® 60 Coated Glass | MSVD | | *Solarban*® 67 Coated Glass | MSVD | | *Solarban*® 70XL Coated Glass | MSVD | | *Solarban*® 72 Coated Glass | MSVD | | *Solarban*® R100 Coated Glass | MSVD | In the pyrolytic manufacturing process, the coating is applied to the glass ribbon while it is being produced on the float line and the coating then “fuses” to the hot glass surface. The glass is then cut into stock sheets of various sizes for shipment to fabricators. For pyrolytic coatings, *Sungate*® 500 and 600 coatings are very durable, both mechanically and chemically. And, while Sungate® 500 and 600 coated glasses offer reduced emissivity and some solar control, they do not perform quite as well as Magnetic Sputtering Vapor Deposition (MSVD) by Vitro Glass. In the MSVD process, the coating is applied to pre-cut glass (usually in stock sheets for further fabrication) in a vacuum chamber at ambient plant temperatures. MSVD coatings such as Sungate® 400 and *Solarban*® 60 low-e glasses offer lower emissivity and superior solar control versus pyrolytic. However, MSVD coatings are not as durable as pyrolytic coatings, either mechanically or chemically, and must always be used as a component of an insulating glass unit with the coating located within the sealed airspace. Do all low-e coated glasses look the same? No, they do not. Color differences between various low-e coatings are due to the use of different coating materials and the thickness of the various coating layers, as well as differences in manufacturing processes. How much does low-e glass by Vitro Glass reduce the transmission of ultraviolet (UV) energy? The reduction in the transmittance of UV energy is dependent on the specific low-e coating by Vitro Glass and the make up of the insulating glass unit, i.e., glass thickness, glass type, etc. Please refer to the [product performance charts](http://www.vitroglazings.com/en-US/Glass/Product-Overview-Applications/Product-Overview.aspx) for specific information. Can tinted glass be used with low-e glass? Yes it can. Tinted glass can be used as the outdoor lite in an insulating glass unit, with low-e glass by Vitro Glass as the indoor lite. The low-e coated glass improves the insulating properties of the insulating glass unit, while the tinted glass reduces the influx of solar energy through the insulating unit. How effective is tinted glass with low-e coatings by Vitro Glass? - Tinted glass is very effective when used in conjunction with low-e glass by Vitro Glass. This combination will reduce excess heat gain and lower cooling costs. - The tinted glass reduces the amount of excess heat gained on the east, west and south exposures - Tinted glass can provide improved glare control, if needed. 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