I have been told that I need to use a 'low-E' glass in my home, what does this mean and is it far more expensive?

A low-E glass is a glass with a special coating designed to reflect heat back into the room, thus reducing heat loss. The extent to which low-E glass reduces heat loss is measured by the U-value, the lower the U-value the better the thermal insulation. You are required to have a low-E glass in your windows to comply with the latest Building Regulations. These new regulations have been introduced to reduce CO2 emissions associated with heating.