Frequently Asked Questions
1. On which surface do you recommend applying the Low-E coating? Is your pyrolytic Low-E available on tinted or reflective glass?
Pilkington Eclipse Advantage™ Reflective Low-E Glass is a pyrolytic Low-E coating on a wide range of tinted glass options that combine solar and thermal control properties in single coating.
Pilkington Energy Advantage™ Low-E Glass is only available on clear substrate. In a clear insulated glass unit, it can be applied to the #2 or the #3 surface; the resulting winter u-value is the same with a slightly lower shading coefficient if the coating is placed in the #2 position. In many commercial applications, a tint or reflective product is required which already allows for a lower shading coefficient. In which case, the #3 position for the Low-E coating would be our recommendation.
A common example of this is Pilkington Arctic Blue™ High-Performance Tinted Glass as the outboard lite, with Pilkington Energy Advantage™ Low-E on the #3 surface of the inboard lite.
(For additional information, please reference Pilkington Architectural Technical Services bulletin #135 "Handling, Inspecting and Fabricating Pilkington Energy Advantage™ Low-E Glass).
In residential applications, a good rule of thumb to follow is to put the coating on the #3 surface if heating bills exceed cooling bills, and on the #2 surface if cooling bills exceed heating bills. If heating and cooling costs are equal, the coating may be placed on either surface.
2. On which surface do you recommend applying the Eclipse Advantage™ reflective coating?
Pilkington Eclipse Advantage™ Reflective Low-E products are pyrolytically coated. All of the Eclipse Advantage™ products (with the exception of Gold Eclipse Advantage™ Reflective Low-E Glass) should be provided with the coating on the #2 or #3 surface. Typical usage is a #2 surface application which allows the base color to be more apparent and provides more subtle reflectivity. For additional information, please reference Pilkington Architectural Technical Services bulletins
3. What is the difference between heat strengthened (HS) and fully tempered (FT) glass? How do I determine which is needed for my project requirements?
Both processes increase the strength of glass (FT is 4 times as strong as annealed glass of the same thickness and configuration; HS is twice as strong as annealed glass of the same thickness and configuration). NOTE: Heat treating of glass does NOT change the stiffness of the glass and amount of deflection under load as compared to annealed glass. Heat treating of glass is commonly classified in 2 types (FT=Fully Tempered, and HS=Heat Strengthened): FT is more commonly used in safety glazing applications since its breakage pattern results in innumerable small fragments of more or less cubicle-shaped pieces of glass which may vacate the opening (Please check local code requirements for approval to use FT glass as a safety glazing material.). HS glass is used in areas where FT breakage patterns would not be desirable, for example, spandrel applications. HS glass has a breakage pattern similar to standard annealed glass. Either of these methods is typically sufficient to address particular thermal stress concerns although, on rare occasions, even tempered glass can break spontaneously, without any applied load, due to small inclusions that may be present in all float glasses. For additional information, please reference Pilkington Architectural Technical Services bulletins
4. What is a shading coefficient (SC) and how does it compare to the solar heat gain coefficient (SHGC)? Does a lower shading coefficient mean less visible light?
Glazing that blocks greater levels of solar energy have lower shading coefficients. The shading coefficient is the ratio of solar heat gain admitted through the glass as compared to the solar heat gain admitted through 1/8" clear glass (1/8" clear glass = 1.0 Shading Coefficient). The SHGC is similar to the SC, but also accounts for absorbed, convected, and inwardly radiated solar energy. The SHGC can be calculated by multiplying the SC x .86 (SHGC=SC*0.86). Both the SC and the SHGC are values which represent the solar heat gain through the glazing from the total solar energy spectrum. They do not necessarily have a direct correlation to visible light transmittance. A good example of this is Pilkington EverGreen High-Performance Tinted Float Glass, which allows for a higher visible light transmittance and, at the same time, a lower SC than a typical bronze or grey tinted glass. For more information, please reference the Pilkington "Glass in Architechture" Product Catalog
5. How much does your glass cost?
Pilkington is a primary float glass manufacturer. We supply our glass in a non-fabricated, non-assembled form to our customer base, who then perform any fabrication of the glass as required (cutting of glass to the proper size, heating treating, insulating glass, or laminating). We would recommend contacting a local glazing contractor to assist you with any budget information.
6. What is your recommendation for spandrel glass and how do I minimize banding? How can I get a sample of it?
As a primary float glass manufacturer, Pilkington does not fabricate typical spandrel glass. Spandrel panel applications can be addressed in various ways: ceramic frits, polyester or silicone based coatings, or without a coating in a shadow box application. For additional information, please refer to In order to minimize banding, one method is outlined in , which includes using Pilkington Eclipse Advantage™ reflective products on the outboard lite with the spandrel coating on the #4 surface of the insulated unit. Should you require a sample, we would recommend contacting a local spandrel fabricator, or your Pilkington Product Specialist for more information.
7. How do I get samples of your glass products?
You can obtain samples of Pilkington products by contacting your area Pilkington Product Specialist.
8. What's the difference between a hard coat and a soft coat?
A hard coat is a pyrolytic coating applied on-line during the initial glass manufacturing process. Since the coating is applied while the glass is in the semi-molten state, it becomes part of the glass surface. A soft coat is a sputtered process that is applied in a batch method after the initial glass manufacturing. The sputter coating is not integral to the glass surface, but rather is a surface coating. There are advantages and disadvantages to both coating options. Please contact Pilkington Product Specialist for more information. For more information on pyrolytic coatings, see The Pyrolytic Advantage.
9. How does Low-E glass work?
Heat energy is comprised of long and short wave radiation. Low-emissivity coatings help reflect the long wave heat energy back towards its source. The primary purpose of Low-E glass is to improve the insulating value (u-value). For more detailed information on Pilkington Energy Advantage™ Low-E Glass, click here.
ATS Bulletin #135 - "Handling, Inspecting, and fabricating Pilkington Low-E Glass
10. What is the standard specification for flat glass? Can you assist me with writing a glass specification? How do I know which performance numbers are the most critical for my project?
The standard specification for flat glass is ASTM C-1036, and we know it can be somewhat complex and confusing. That's why we developed the Pilkington Sun Management™ Calculator. This program will automatically calculate the performance data for any combination of 1/4" glass products, glazed monolithically, or in an I.G. unit with either clear float or Energy Advantage™ Low-E Glass as the inboard lite. Then, when you've found the combination that best meets your aesthetic and performance requirements, the program will generate a customized, formatted specification. For other thicknesses or special applications, we would be happy to assist you with the development of your glass specification and can provide this information in the Division 08810 format, or assist you with your performance data requirements. Please contact your area Pilkington Product Specialist.
11. How available are your products? (lead-times?)
Pilkington's products are readily available through our fabrication customer base. Since our coated products are pyrolytically coated, they are typically an inventoried product and can be fabricated, heat treated, etc. at any time. For more information on The Pyrolytic Advantage, click here.
12. How do I handle glare issues?
Glare has a direct correlation to visible light transmittance. Lower visible light transmittance results in less glare. One of our most effective products to control glare is Pilkington SuperGrey™ High-Performance Tinted Float Glass.
13. How can I best minimize glazing costs no matter what glass is selected?
Float glass is produced in a continuous ribbon process with a standard width of 130" in North America factories. Therefore, most standard shipping sizes include one dimension of 130". If you design your projects with awareness that maximizing the ribbon width (130") results in greater utilization of production, higher optimization can be realized and is usually figured into the cost to produce the final product. For example, a design requiring 60" in glass width will result in two pieces of glass across the ribbon or 120" in total - a 92% yield of the 130" dimension. A size that requires 69" in glass width may result in a single piece of glass from the 130" dimension - a 53% yield of the 130" dimension. The better the yield the lower the cost and the better chance for you to maximize your return on glass investment. For further assistance regarding this cost saving suggestion, please contact your local glazing contractor or your Pilkington Product Specialist.