The good news is that many new types of high-performance window glazing have been produced in recent years, making possible the use of glass without the accompanying severe heat loss, heat gain, and glare.

Whether you are remodeling, building a home, or simply replacing windows, you may choose from a wide variety of high-performance glazing.

The basic measurements of performance are R-values and U-vales. For an explanation of these, see Window R-values and U-values.

In addition, other measurements are used with glass, including a "light-transmittance" value that rates how much light the glazing allows, and "shading coefficient" and "UV value" that measure the amount of glare and ultraviolet light allowed through the glass. Talk with a window dealer about the specific properties and values available.

Generally speaking, if you want to minimize heat transfer, pick high-performance glazing that has a high R-value. For maximum light, choose a type with a high visual light-transmittance value or, to cut glare, with a lower light transmittance value. To cut heat gain, select glazing with a high shading coefficient. Glazing with a high UV value will block nearly all furniture-fading ultraviolet rays.

Basic insulating glass may have two or three panes separated by an air space. Dual-glazed have become the standard for performance; triple-glazed windows are, of course, better performing but are relatively expensive and heavy to handle during installation. Beyond these varieties, consider these:

-- Low-E glass has a virtually invisible metallic coating that blocks radiant heat transfer and protects carpets and furnishings from fading by reducing damaging ultraviolet rays from the sun. "Super" windows have two low-E coatings to achieve incredibly high R-8 insulation values.

-- Even more efficient insulating windows have Argon gas, a natural, colorless, non-toxic gas that is sealed between glass panes.

-- Insulating low-E glass filled with Argon gas has about twice the insulating qualities of standard dual glazing.

-- Solar bronze and solar gray tinted glass help keep out unwanted heat and ultraviolet rays. If there is a possibility of ultraviolet (UV) damage to floors, rugs and furniture, consider choosing a glazing that resists UV rays--either one of these tinted types or a low-E glazing.

Of course, you will find decorative possibilities, too, including etched, beveled, leaded, and many other ornamental glazing materials. Divided lights are popular, particularly for a house that has a traditional architectural style. For doors, both single and double-glazed windows are available with either real muntins (divisions between glass panes) or snap-in wood grills that make windows less expensive to buy and easier to clean. Speaking of cleaning, you can buy glass that has a polymer coating that repels dirt, minimizing the need for window washing.

You can also buy windows that have integral shades or dual-glazed windows with mini-blinds positioned inside, between the glass panes. These are great for rejecting glare and heat gain on hot, sunny afternoons. --DV

See more about Buying Window Glass:

• Window Glass Buying Guide
• Safety Glass Windows
• Stained Glass Windows
• Tinted Glass and Reflective Glass
• Window Film
• Window R-Values and U-Values