The Effect of Low-E Glazing on Energy

How it Works

• Low-E glass has a microscopically fine coating of metal on one side. This coating allows light through, but blocks heat. This means you save energy cooling your home in the summer, as the windows don't let in as much heat. In winter, heat can't escape as easily, so you save energy on heating.

Types

• Two main types of Low-E glass exist: hard coat and soft coat. Hard coat Low-E glass uses tin to block the transmission of heat. Soft coat uses tin, zinc or silver. Soft coat glass is a better insulator than hard coat glass, saving you more energy.

Manufacture

• Hard coat glass is made by pouring a layer of tin over the glass while it's still partially melted. Soft coat glass is made by placing the glass in a chamber filled with electrically charged gas. Atoms of tin, silver or zinc are then sprayed (or sputtered, as it is called) onto the glass, where they stick in a fine layer.