Your Window Glass Options are Clear (or Tinted, Energy Efficient…)

There's more to window glass than meets the eye. Those clear panes conceal different glazes and layers, and even chemical compositions. The type of glass ("glazing") you choose will determine how well your windows insulate your home, protect against the elements, and withstand wear and tear.

Glass Ratings
New glazing technology has done wonders to improve the performance and energy efficiency of glass windows. To determine how effective a particular window is, simply check its energy-efficiency rating.
     •      R-value measures a material's resistance to heat transfer; the higher the R-value,              the better the insulation.
     •      U-value evaluates overall energy efficiency by measuring heat loss through the              entire window, including the frame.
If you live in a cold climate, a high R-value and low U-value will likely be worth the investment.

Three Factors in Glass Quality
A window's energy efficiency is determined by three factors: the glazing layers, material, and coating.

Glazing Layers. The more layers, the more effective the insulation. Single, clear glazing provides the least protection from the elements, with a rating of R-1. A double pane window can cut heat loss in half, or by even more if the air space between panes is filled with a low-conductance gas such as Argon. Triple, clear glazing introduces a middle layer of glass or plastic film.

Glazing Material. Clear glass is the classic glazing material, but tinted glazing is a more effective barrier to solar glare and heat. Heat-absorbing glass contains a special tint that absorbs nearly 50% of incoming solar energy.

Coating. Reflective and Low-Emissivity (Low-E) coatings improve window performance in both the heating and cooling seasons. Reflective film reduces light and prevents heat gain. Low-E glass allows full light, but reduces heat transfer considerably. Low-Emissivity glass transmits 40% to 70% less heat than clear, untreated glass.

Combinations of these features produce a wide array of efficiency grades to suit every climate and budget.

Sources:
EfficientWindows.org
Replacement Window Center