Triple glazing is different to double glazing as it contains three panes of glass within a sealed frame, whereas double glazing contains just two. Between each pane what is found is a pocket of air or inert gas, such as argon; argon is heavier than air and works as an insulator for noise and heat.
We are gradually being encouraged to upgrade from double to triple glazing. Noticing that the pressure is on to enhance the energy performance of windows and that we are now reaching the stage where double glazing windows will now not be enough as triple glazing has an embodied energy approximately 50% higher than double glazing.