In keeping with today's concerns for saving energy, windows may be standard single glazed, dual glazed or even triple glazed.
"R-values" measure heat loss through glass: the higher the R-value, the higher the glazing's resistance to energy loss. By increasing a window's R value from 2 to 4, you can cut energy loss by 50 percent.
Low-E glass has a virtually invisible metallic coating that reflects heat and protects carpets and furnishings from fading by reducing damaging ultraviolet rays from the sun. 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.