Insulated Glass Units (IGU) as they are generally called in the North America is also referred to as a double glazed units.
These IGU have very high heat retention properties.
This is desirable since the cost to produce energy has significantly risen in the past few years.
Insulated units creates a High-Performance window which can save a home owner upwards of $500 to $600 annually.
The reason why the IGU's are so efficient in comparison to a single pane, is because of the space between the panes of glass.
Insulated glass unit can comprise of two or more panes of glass, each separated by a spacer.
The assemble of a hermetically unit includes a minimum of two panes of glass and a spacer to separate the sheet which creates a controlled "air" space in between the panes.
Depending on this thickness of each pane of glass as well as the width of space between them, the thermal value of the IGU can vary.
The technical term used in the glass industry for IGU are hermetical sealed units.
What this means is the environment within the sealed unit is completely isolated from the that of the exterior.
For a vinyl window to meet Energy Star rating standards, one of the most important components is the gases which is used to reduce the convection process with in the panes.
There are three type of gases which are used to replace are within the sealed units.
These gases are all denser than air therefore they retards the transfer of heat form the interior to the exterior and vice verse.