Argon Gas
An inert gas used to fill the cavity in insulated glass units, providing better thermal insulation than air.
Argon is approximately 34% less conductive than air, making it the most common gas fill for residential and commercial IGUs. It is colourless, odourless, and non-toxic. Over time, argon can slowly leak from sealed units at a rate of about 1% per year.
Krypton gas offers even better insulation but is significantly more expensive, making it most common in triple-pane units where the cavity is narrower. Most Canadian window manufacturers offer argon fill as a standard feature.