Energy efficent sealed units:
Energy efficient units are gas filled (argon gas) units which improve thermal efficiency, it's thermal conductivity is roughly 67% that of air and is inexpensive, making it an attractive gas fill. The pane of glass which is applied in a gas filled unit is low e-glass, which has many advantages, low e-coating reflects heat back to it's source so it helps your home stay cooler in the summer and warmer in the winter, which helps keep those heating bills down.
The second pane is usualy 4mm float optiwhite glass or 4mm optiwhite toughened glass, optiwhite glass is a low iron extra clear float glass with a very high light transmission and optimum vision quality is achevied when looking through the glass. There are two types of spacer bar, aluminum spacer bar and warm edge spacer bar. Aluminum spacer is the most commom bar, but warm edge does insulate the double glazed unit up to 40% more than the aluminum bar.
Energy efficent double glazed units come in different grades, for example if you wanted an A-grade double glazed unit that would consist of 4mm low e, 20mm warm edge bar, 4mm optiwhite argon filled gas. A double glazed unit consisting of 4mm low e, 20mm aluminum bar, 4mm optiwhite would be a grade C unit, both of which would pass for when you are having new pvc frames fitted, basically whatever your budget - there is a d.g.unit to suit!
