Cooler in Summer / Warmer in WinterDouble Glazing consists of two layers of glass with a spacer in between.  The spacer contains a desiccant  This acts as a drying agent, keeping the window free from moisture.

The space between the two layers of glass is sealed and contains air or a gas, such as argon.  The seal is important.  If this is compromised, moisture can form on the inside of the glass.

The air (or argon) gap acts as an insulation layer.  The result is improved insulation from the elements outside your home.  Thus your home is warmer in winter, cooler in summer and condensation is virtually eliminated.