Building Green with Windows and Doors

With the growth of Green Building, windows and doors take on an increasingly significant role for occupants' well-being and energy efficiency.
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Advertorial course provided by Marvin Windows and Doors
Karin Tetlow

There are two basic types of low-E glass. The first, vacuum or sputter coated low-E, referred to as soft coat, is a coating added after the glass has been manufactured. The second is pyrolitic low-E, commonly referred to as hard coat, which is fired into the glass while it is still in a molten state. Many low-E coatings including hard coat can be tempered without destroying the low-E coating. Hard coat is more reflective. It can be used in an energy panel or combination while soft coat can only be used in insulating glass. Manufacturers are working on new technologies to overcome this limitation.

The current generation of low-E comprises two or more panes of glass in an insulating unit with an unnoticeable low-E layer that screens solar heat gain during the summer season and heat loss during the winter season.


How high performance low-E glass functions in summer and winter.
Courtesy of Marvin Windows and Doors

*High performance low-Eglass is characterized by two or more panes of glass coated with microscopic metal or metallic oxide layers to reflect or absorb the sun's warmth, as well as reduce the damage from UV rays. It blocks long wave infrared inside and short wave solar heat outside. This results in keeping heat inside during the winter and outside during the summer, thus reducing air conditioning demand and energy, and increasing comfort level by reducing the glass temperature.

High performance low-E treatment can add a 51 percent improvement to winter thermal performance and a 47 percent improvement to SHGC.

*Gas-filled airspace. Argon or krypton (colorless and odorless gases naturally occurring in the atmosphere), is used to fill the airspace between layers of insulating low-E glass. This greatly increases insulating performance by slowing the transfer of energy through the unit. Laminated glass construction further enhances the sound reduction characteristics of the insulating glass unit.

Breather tubes are required on insulating units that will be installed at high altitudes. The breather tubes allow the unit to adjust to changes in pressure. Argon gas is not an option when breather tubes are specified.

*Tinted glass. A bronze, gray or other-tinted glass can lower the SHGC of a window significantly and can help control glare. Visible light transmittance will vary from 14 percent to 85 percent depending on color and thickness. As glass thickness increases, color becomes darker. The glass is tinted through the entire lite, not just on the glass surface. Tinting is usually done on the exterior lite on an insulated glass unit. No published color standard exists, but typical colors produced in the U.S. include bronze, gray, dark gray, aquamarine, green, deep green, blue and black.

 

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Originally published in Architectural Record.
Originally published in June 2006

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