Argon is an inert, non-flammable, non-toxic gas that constitutes about one per cent of the air we breathe. When the space between the two panes of glass is filled with Argon gas, it acts as a thermal blanket that reduces heat transfer.
How does it work? Argon gas is less conductive than regular air. If you fill the space between the two sheets of glass with Argon gas, you will have less heat conducting through the Argon gas from the warmer glass surface to the colder glass surface than you would have through air. Thus, heat loss through the glass-Argon-glass in the winter is lower and in the summer, the heat gain from the outside to the inside is also lower.
Another savings is made due to the fact that Argon gas is heavier than air, reducing convective heat loss between the two sheets of glass. In the winter for example, the interior, warmer glass heats the air next to it in the air pocket, causing the air to rise. The air warms the exterior cold glass surface and that air mass falls as it looses heat. These convection currents occur in the air space between insulating double glass sealed units. Since Argon gas is heavier than regular air, when you fill the insulating glass air space with Argon gas, the convection pace is dramatically slower. Thus, the heat loss is slower both in the winter from your heated home or by slowing the entry of heat on sizzling summer days.
Another property of Argon gas is its ability to filter more of the damaging ultraviolet rays than regula air, preventing draperies and carpets from fading. Therefore, we strongly suggest using Argon gas in combination with "Low-E” glass to keep the heat where you want it.