The use of inert gases (argon and krypton) is something most homeowners find confusing as they're trying to learn about windows. I'll try to briefly explain a little about these gases and why they are used. First of all, both are completely safe. In fact, each one is present naturally in the atmosphere. Argon actually makes up about 1 percent of the atmosphere; krypton is there in trace amounts. 

The reason some window manufacturers insert an inert gas into the air space of double-pane windows (or into the two air spaces of triple-pane windows) is to make the window more energy efficient.  In windows with just air between the panes, heat causes currents (or movement) of the air and allows for conduction of heat and cold.

Argon and krypton, on the other hand, are denser than air.  When they are used between the glass panes of a window, the currents are much slower, as is the conduction of heat and cold. This helps to keep heat from being conducted from the inside glass of the window to the outside glass in cold weather. In warm weather, conductivity of outside heat is slowed to help prevent it from reaching the inside pane. This keeps your home cooler in warm weather.

At Gorell, we use argon or krypton (and sometimes a unique blend of the two) in all of our windows that are made with Low-E glass. The combination of Low-E-coated glass and an inert gas between the panes is very effective for manufacturing windows that make homes more comfortable and energy efficient.  It also helps qualify Gorell windows for the ENERGY STAR label, ensuring less home energy consumption. Depending on the price of energy, that usually means lower energy bills!