Triple glazing follows the same basic concept as double glazing, only instead of two layers of glass with a separating layer of air in between, you have three layers of glass with two layers of air in between.
Triple glazing is not something that you find very often in the UK (which is still busy updating all of their windows to double glazing), but in other countries where keeping homes warm is a common concern, such as in Norway, it is very commonplace.
Triple glazing is used because, as with double glazing in comparison to single pane windows, it offers even greater improvements in heat retention than even double glazing. With laws being developed which could potentially come into play regarding heating efficiency in new homes, this could be one area worth looking at.
Unfortunately, as with double glazing, the increased cost of using triple glazing is large when compared to standard windows. It is still a great investment however, as the lifespan of the product still far outstretches the point at which you’ll have made your money back in heating savings.