Low-E Coated Glass
With low-E coated glass, building designers can improve natural light transmittance and increase solar performance. ITI Glass stocks several low-E glass types and carries the full line of Solarban® products as a member of PPG Industries Certified Fabricator Program.
Low-E (low-emissivity) glass selectively transmits visible light and filters short- and long-wave radiation from the sun — the main causes of heat gain and sun damage in buildings. Before low-E, tinted and reflective coated glasses were commonly used to improve the solar performance of a window. Naturally, darker tints improve solar performance at the expense of visible light transmittance. With low-E performance glass, building designers can strike a desired balance between visible light transmittance and solar efficiency.
How Low-E Works
Low-E glass increases a window's efficiency two ways: First, by reducing the amount infrared radiation that transmits, low-E glass decreases the total amount of heat gain through a window. Second, low-E glass minimizes heat loss and the effects of the outdoor climate on a building's controlled interior temperature by reflecting heat back to its source. In this capacity, low-E acts as a transparent barrier between indoor and outdoor climates, reducing heat transfer through a window.
ITI Glass manufactures all hard coat and soft coat low-Es in accordance with ASTM C1376-03 Standard Specification.
MSVD & Pyrolytic Low-E
There are two types of low-E coatings, hard coat, or pyrolytic; and soft coat, or MSVD (magnetron sputter vacuum deposition). Appropriate specification of architectural glass should maximize energy efficiency without sacrificing interior daylight transmittance. This can lower energy use of regulated heating and cooling systems and reduce or eliminate the need for electric lighting.
» Heating-degree days
» Cooling-degree days
Hard coat low-Es perform most efficiently in climates where interior heating is most important by allowing higher levels of infrared radiation to transmit. This results in more effective use of natural heating from the sun. However, if lower U-Values are desired for more efficient thermal insulating, a soft coat low-E should be specified.
Soft coat low-Es are distinguished by higher Light to Solar Gain ratios and lower U-Values. These perform best in climates where interior cooling and thermal insulation are most important. By effectively reducing infrared transmittance, soft coats reduce the overall heat gain through a window. This can decrease the energy use of regulated cooling systems. Soft coats also reflect interior heat back to its source, resulting in less radiant heat transfer and more effective insulating performance.
3rd vs. 2nd Surface Low-E
Whether hard coat or soft coat, specifying low-E coatings on the second-surface of an insulated glass unit effectively improves solar performance values and increases the glazing's spectral selectivity, a desired performance in warm climates. Second-surface coating positions result in improved Shading Coefficient and Solar Heat Gain Coefficient values, as well as higher Light to Solar Gain ratios.
Because of the improved performance values afforded by second-surface low-E coatings, demand for low-Es on tinted substrates has increased. Generally, in an insulated glass unit, the outboard lite of glass is tinted. To specify low-E on the second surface of a tinted unit, the coating must be applied to the tinted substrate. ITI Glass stocks a variety of tinted low-E substrates. However, availability varies. Contact customer service for specific product lead times.
PPG Solarban® Low-E
Member of PPG Industries' national network of Certified Fabricators, ITI Glass supplies the entire line of Solarban low-E products, including Solarban 70 XL, a product that achieves the industry's highest Light to Solar Gain ratio. PPG's entire line of architectural glass products are Cradle-to-CradleCM Silver certified for environmentally responsible material content, recyclability and manufacturing characteristics. This can be used to earn points for LEED® projects. For more information, visit www.c2ccertified.com.
