Insulated windows or double-glazed windows (as they are commonly called) have become increasingly popular in the last decade. Unlike traditional windows, these contemporary counterparts contain panes of glass with the space between the panes filled with inert gasses such as xenon, argon, krypton to form an airtight seal. These windows come framed in materials like aluminum and uPVC and act as an insulating barrier between the interior and exterior of the building.