Nitrogen Gas in Double Panes

• Though nitrogen gas is used in car tires to improve performance, double-pane windows typically do not use nitrogen gas in between the panes. Nitrogen is not thought to affect the energy efficiency of the windows. For this reason, it has little place inside the panes. To improve the energy rating of the window, the gas has to be proven to stop heat transfer. The gas' ability to prevent heat transfer adds to the total efficiency of the window.
  
  

Argon in Double Panes

• Double-pane windows do use argon gas as an insulator in between the panes. Argon gas is shown to stop heat transfer, so it does improve on the efficiency ratings of the windows. The argon gas helps to insulate the glass panes to stop heat loss and improve cooling efficiency. The addition of argon gas to double-pane windows increases the price of the windows, because the manufacturing process is more expensive. Argon-filled window panes cost up to $850, as of August 2011, depending on other factors and materials used in their construction.
  
  

Adding Argon Gas to Double Panes and Seal Integrity

• Adding gas to window panes requires technical expertise and special equipment. Gas is injected inside the panes before the window is sealed. This seal prevents the gas from escaping. However, temperature changes affect the integrity of the seal. As temperatures rise and fall, the seal naturally expands and then contracts, gaps eventually form in the seal and the gas escapes. Now, air travels through the gap, and it draws in water vapor, causing condensation inside the window panes. If you see vapor inside your window panes, replace the windows because it is a sign the window has failed.
  
  

Air in Double Panes

• If argon gas is not used in the window panes, air takes its place. Air is also a gas technically speaking, but it is not considered a special insulating gas. Air will naturally fill the space in the panes during construction, so it does not have to be injected into the panes in a sealed environment. Dry air will not cause condensation inside the window panes as hot and humid air will. Manufacturers build the windows with this in mind, taking steps to ensure humidity is under control during manufacturing.