Low-E coatings are microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow. The principal mechanism of heat transfer in multilayer glazing is thermal radiation from a warm pane of glass to a cooler pane. Coating a glass surface with a low-emittance material and facing that coating to the airspace between the glass layers blocks a significant amount of this radiant heat transfer, thus lowering the total heat flow through the window. Low-E coatings are transparent to visible light. Different types of Low-E coatings have been designed to allow for high solar gain, moderate solar gain, or low solar gain.

This figure illustrates the characteristics of a typical double-glazed window with a high-transmission, Low-E glass. These Low-E glass products are often referred to as pyrolitic or hard coat Low-E glass, due to the glass coating process. The properties presented here are typical of a Low-E glass product designed to reduce heat loss but admit solar gain. High solar gain Low-E glass products are best suited for buildings located in heating-dominated climates.

This Low-E glass type is also the product of choice for passive solar design projects due to the performance attributes relative to other Low-E glass products which have been developed to reduce solar gain.

Arch's Passive Low-E's

• Pilkington Energy Advantage
• Pilkington Solar-E
• AFG Comfort E2
• PPG Sungate 500

Some Available Thicknesses
1/8" (3.0mm), 3/16" (5.0mm), 1/4" (6mm)