Double glazing is the standard for most properties now from smaller windows right through to larger French doors. Double glazing essentially uses two panes of glass with a few millimetres of air in between them (or a special gas like argon). Having an additional layer and the argon gas or air in the middle means that is it harder for things to escape through the French doors. This is great for keeping out draughts, the cold weather won’t enter your house as easily and the heat won’t escape your house as quickly. This is especially important for outside noise as well.