Only one window was the only option for windows, but not anymore. Double glazed windows have become very popular in new builds and as replacement windows over the years, due to their energy-saving properties and other benefits, such as noise reduction. The double glazed windows are very good insulators, keeping the air warm and the air cold. What makes them so effective insulators? Part of the answer does not lie in the glass itself, but in the space between the two panes.
The space between the two panes in a double-glazed window is usually about half an inch wide, and is usually filled with argon or other inert gas . These gases are non-toxic, non-reactive, clear and odorless. Argon is also inexpensive, making it a common choice for this purpose.
Inert gases are heavier and denser than air, so their molecules do not move as easily. The presence of inert gases between the windows makes it more difficult for warm 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 a lower heat loss, the R-value of the window, which measures its resistance to heat flow, is increased. A higher R value means a more energy-efficient window. A single panel glazed window typically has a R value of about 0.85, and a double glazed glazed window without argon fill can have a R value between 1.5 and 2.0. A double glazed glazed window with an argon gas filler is considerably more energy efficient, as evidenced by its higher R value, between 2.7 and 3.6.