What is Low Emmisivity (Low-e) Glass?

A Low Emmisivity Glass is Glass that has had a microscopic layer of metals applied to a surface of the Glass. The low-emmisivity restricts the ability for long wave energy to pass through glass, this has the affect of stopping heat either passing into (in a hot climate) or out of (in a cool climate) your house. Long wave energy is the energy that radiates from a hot road in summer or is emitted by your heater during winter and low-e coatings allow you to keep this energy in during summer and out during winter. The coating also allows short wave energy (light and Solar Heat) to enter the house. Once this energy has entered the house it encounters the contents of the house and is broken in longer wave energy, which cannot escape back through the windows.