Low-e Glass Windows
Low-e glass windows come pretty standard on most replacement windows today. Low-e stands for low emissivity and the glass basically does one of two things. It either lets heat pass through the glass or prevents it from entering. The right low-e glass for your replacement windows will be based primarily on where you live and the climate, as well as what you are willing to spend.
Low-e Glass Options
There are three types of low-e glass; low-e, low-e2 and low-e3. The higher the number, the darker the tint on the window. The darker the tint on the window, the more UV rays and heat are refelected and therefore don't enter the home. This has an obvious impact on the overal energy efficiency of the windows. The higher the number, the more expensive the cost of each window.
Low-e Glass Costs
The cheapest replacement window option is clear glass, which has no tint to it. Low-e glass will add $50 on average to the cost of each window you purchase. An upgrade from low-e to low-e2 will add $25 on average and to go from low-e2 to low-e3 you can expect to add another $25 per window.
In hot climates such as Texas, Florida or Arizona, homeowners may want to consider a low-e glass with a soft coat that would help reflect as much heat and UV rays as possible.
Low-e glass is perhaps just as important in cold cimates where preventing heat from escaping the home is the important goal. All home window glass has a SHGC or solar heat gain coefficient that must be the right number to maximize heat gain or loss.