Double glazing is twice or more as effective as single glazing in terms of heat insulation.

Double-paned glass, known as double glazing, is twice as effective as single-paned glass, or single glazing, in terms of heat insulation. The reason for this is due to the use of two panes of glass versus one, as well as to the layer of air that is sandwiched between the two panes.

The dry air trapped between the two glass panes helps curb the transfer of heat. It works like a down jacket helps keep you warm, with the warmth provided by the jacket through the small pockets of air within the down that curb heat transfer.

Low-E stands for Low-Emissivity. Emissivity is a measure of how much a glass surface transfers radiant heat. The less radiant heat is transferred, the better. The surface of Low-E double glazing glass is coated with a special metallic layer that further lowers heat transfer (thermal emission) and demonstrates superior insulation properties compared with standard double glazing.

Owing to stronger energy efficiency standards, the number of new homes being built with double glazing in Europe, the United States and Japan is increasing. However, most existing houses still use single glazing and continue to face the issue of inefficient heaters and heat loss.

The vacuum principle helps boost the thermal insulation efficiency of double glazing.

In 1997, the NSG Group became the first company in the world to successfully develop vacuum glass, which it named SPACIA. SPACIA vacuum glass applies the principle that makes a thermos bottle effective, namely, that a vacuum does not transfer heat. Accordingly, the layer of dry air between the two panes of double glazing has been replaced by a vacuum.

There are three ways in which heat, or thermal energy, is transferred. The first is conduction, exemplified by heat passing from one object to another without the objects actually moving, such as when the handle of a heated frying pan becomes hot. The second is called convection and explains why the heat from a hot bath flows from the hot water to warm up the surrounding water. Third, is emission, which is heat radiation, such as the way an open fire radiates heat. Consequently, the more efficient glazing is at curbing all three types of heat transfer, the higher its insulation properties.

The vacuum layer of the vacuum glass works better than a simple layer of dry air to curb conductive and convection types of heat transfer. SPACIA 21, which was developed after the original SPACIA, is a hybrid of our vacuum glass and Low-E double glazing and achieves superior thermal insulation properties. Owing to the functioning of the Low-E film coating, not only is SPACIA 21 effective in curbing conduction and convention heat transfer, but also heat emission.

SPACIA 21 vacuum glass, boasts eight times, four times, and two times the thermal insulation of single glazing, standard double glazing and Low-E double glazing, respectively.

 

CSR Report 2007