Triple glazing coated glass

·         commonly known as double

·         are double or triple glass window panes separated by an air or other gas filled space to reduce heat transfer across a part of the building envelope.

http://en.wikipedia.org/wiki/Insulated_glazing

Benefits:

•     Wider cavities between the two glass panes 16mm is the optimum distance

•     Low-emissivity coatings being added to the glass to stop heat escaping

•     The cavity being filled with an inert gas, usually argon

•     Designing out cold bridges (aluminium spacers etc) surrounding the glazed units

•     improved overall thermal efficiency of a building envelope

•     Keep heat out during summer

•     Improved security over double glazed windows

•     Better sound insulation over double glazed windows

http://www.homebuilding.co.uk/advice/key-choices/green/triple-glazing

Disadvantages:

•          reduces solar gain

•          reduces light transmission

•          increases the need for artificial lighting

•          produce more energy from solar gain than they lose through heat loss. They can be produced using current window types and styles at relatively small increased costs. Lowering U values beyond this level produces disproportionately large cost increases as the table shows.

http://www.secure-style.co.uk/index.php/products/triple-glaze-vs-double-glazing