What is Low-E glass?
Low-E glass is one of the technological marvels of today’s residential construction. The "E" is for "Emissivity" and the dictionary defines emissivity as "the relative power of a surface to emit heat by radiation." Low-E glass works by reflecting heat back to its source. It does this by utilizing a coating of microscopically thin, optically transparent layers of silver sandwiched between layers of anti-reflective metal oxide coatings. These "smart" coatings provide optimal year-round energy savings by filtering the suns energy in summer and reducing heat loss in winter. In the summer low-E products let in visible sunlight while blocking infrared and ultraviolet solar energy that drives up cooling costs and damages curtains, window treatments, carpeting, furnishings and art work. In winter low-E glass reflects room-side heat back into the room.
For example, assume an outside temperature of 0 degrees and a stiff sustained wind of 15 mph blowing against the window. The inside surface temperatures of the different glass assemblies would be as follows:
Single pane :: 26 degrees
Regular double pane insulated glass :: 35 degrees
Soft coat Low-E :: 62 degrees
Obviously, the closer the glass temperature is to the actual room temperature the less convection there will be near the window. Low-E glass simply works.
Larger Window Areas
Because Low-E Glass is an energy-efficient, high performance glass, architects, builders, and homeowners have the freedom to incorporate larger window and glass areas in their designs, without the resulting excessive energy costs.
A Source of Free Energy
In addition to its low U-value, Low-E Glass has a high shading coefficient. Compared to other glass products with lower shading coefficients, Low-E Glass allows more of the sun's rays to enter a home as solar energy to be converted into usable heat in winter.