Types and Parts: Gas Fills
Windows are more efficient when they block air and heat from passing through them. In cold climates, they keep heat inside. In hot climates, they keep it out. In both settings, air conditioners and heating systems won’t have to work as hard to keep temperatures stable, lowering utility bills as a result.
Filling the space between the panes of a double- or triple-glazed window with gas boosts efficiency by reducing heat transfer. Manufacturers use argon and krypton, which block more heat because they are denser than air. Both are safe to use because they are non-toxic, clear, and odorless, and will stay that way even if leaked or mixed with other elements. The Window Selection Tool identifies options for gas-filled windows best suited to your home.
Krypton is the most efficient but also the most expensive. Argon is the popular and affordable alternative, and manufacturers also offer windows with a mix of both gases, to balance premium performance with affordability. Some gas can leak from a window over time, but this is not a safety or health concern because the gases are non-toxic. This leakage will lead to a small drop in efficiency, because the leakage rate for an efficient window is about 0.5% of gas fill per year. However, even after 20 years a window with gas leaks would still perform at 90% of its original capacity.*
*For more information on NFRC’s sources and statistics, the Partners page of this site details the groups with which NFRC’s experts collaborate and share data.