Window GlazingThere are a variety of options for your window glass, too: gas fills, heat-absorbing tints, insulated (double- or triple-glazed), low-E coatings, reflective coatings and spectrally selective coatings.Gas fills. The most common gasses used are argon, which is relatively less expensive, and krypton, which is more expensive but has a better ability at decreasing a window's U-factor.Heat-absorbing tints. These come in colors such as blue, green, gray, bronze or black. Tint doesn't lower a window's U-factor, but inner glass layers or spectrally sensitive coatings can be added to help with that. Gray and bronze reduce heat and light; blue and green allow more visible transmittance (VT) but only slightly reduced heat transfer.