A single pane of glass used to be the only option for windows, but not anymore.
Double pane windows have become very popular in new construction and as replacement windows over the years, due to their energy efficient properties and other advantages, such as sound reduction.
Double pane windows are very good insulators, keeping warm air in and cold air out.
What makes them such effective insulators? Part of the answer lies not in the glass itself, but in the space in between the two panes.
The space between the two panes in a double pane window is usually about half an inch wide, and is typically filled with argon or another inert gas.
These gases are nontoxic, nonreactive, clear, and odorless.
Argon is also inexpensive, making it a common choice for this purpose.
Inert gasses are heavier and denser than air, so their molecules do not move as easily.
Having inert gasses between the panes of glass makes it more difficult for the warmer inside air to pass through the glass to the colder outside.
This helps keep warm air from escaping during the cold winter months, saving on heating costs.
With lower heat loss, the window's R-Value, which measures its resistance to heat flow, is increased.
A higher R-Value means a more energy-efficient window.
A single pane glazed window generally has an R-Value of about 0.
85, and a double pane glazed window without an argon fill may have an R-Value between 1.
5 and 2.
0.
A double pane glazed window with an argon gas fill is considerably more energy efficient, as seen by its higher R-Value, between 2.
7 and 3.
6.