Insulating glass units, or IGUs, are designed to keep homes warmer in the winter and cooler in the summer.

An Insulating glass unit is the most effective way to reduce air-to-air thermal transfer through the glazing. When used in conjunction with low emissivity and/or reflective glass coatings, IGU's become effective means to conserve energy.

An insulating glass unit commonly consists of two (sometimes more) panes of glass separated by a spacer material and sealed together at the edge. The insulating airspace is filled with air or a noble gas, such as argon inside. Each glass pane has two surfaces, so typical double-paned IGUs have four surfaces.

Using argon in the air space between the two panes of glass provides further insulation, as these gases are denser than air and less likely to let heat conduct through the IGU. Combined with a low-e glass coating, these gases work to improve the window's overall u-value, which is a measure of the heat transmission through a building part (such as a wall or window). The lower the u-value, the better the insulating glass unit.

When 90 percent argon gas fill is used in a low-e IGU instead of air, the window's u-value can be improved by up to 16 percent. Similarly, krypton improves the u-value in a low-e IGU by up to 27 percent. However, using a noble gas instead of air in an IGU can add both time and cost to the window's construction.

Insulated glass is available in two type:

• A Double Glazed Unit (DGU ) refers to two pieces of glass sealed around the edges with a perimeter spacer bar (creating a cavity between) to form a single unit.
   
• A Triple Glazed Unit (TGU) refers to three pieces of glass sealed around the edges with two spacer bars (creating two cavities between) to form a single unit.
  
  

Components of Insulating Glass Unit (IGU)

Insulating Glass Unit (IGU), which fits within a window frame, is comprised of seven components:

• A Spacer Bar - a frame that separates the two panels of glass, creating a cavity. The spacer bar can be aluminium or warm-edge.
• Desiccant - a silicon material used in the spacer bar to dry up moisture trapped within the cavity.
• A primary seal - the main barrier to air or moisture migration into the double glazed unit (DGU).
• The glass - clear, solar control, Low E, self-cleaning, acoustic, toughened, laminated or a combination.
• The secondary seal - the main structural adhesive around the outside edge of the unit, holding all the elements together.
• The cavity - the void formed between the component parts.
• The gas filling the cavity - dehydrated air, argon.