How Low-E glass can make double glazing even more efficient

How you can improve the insulation properties of double glazing by using Low-E glass.

Double glazing can halve the loss of heat through your windows. Whilst a small proportion of this saving is in the multi chambered frames and seals, the two panes of glass make the biggest contribution thanks to that all important gap between the two panes of glass in the 'sealed unit' - so called because two panes of glass are bonded to an internal spacing before the whole assembly is sealed around the edge.

The GGF website claims that the optimum space between panes starts at 20mm. A smaller gap will mean more heat loss.

One popular way in which homeowners can increase the efficiency of their double glazing is to choose Low-E glass (Low emissivity glass).

The process involves a microscopically thin coating applied to the gap (or cavity) pointing face of the inner pane of glass.

This special coating reflects longer wavelength heat from the room back into the building, meanwhile, it allows warming short wavelength heat from the sun in. This solar energy converts to longer wavelength heat in your room, which in turn, then isn't allowed to escape back outside past the coated pane.

Many believe that Low-E glass has similar energy saving properties to normal triple glazing, which could be a deciding factor if the extra weight of triple glazed units was a factor in installation.

What's more, Low-E glass is available on not only ordinary glass, but laminated and toughened glass too so it can also be used on patio and french doors - in fact anywhere the specification calls for toughened or safety glass to be used.

Low-E glass double glazing can be improved further still.

Using an inert gas like Argon which is sealed into the air space between the two panes of glass. Argon has better thermal properties than ordinary air and so contributes to a windows lower U value. The lower the U value, the greater the energy savings and thermal insulation offered.

Typical U values (as taken from the GGF - Glass & Glazing Federation website):
Single clear glass - 5.4U
With ordinary double glazing this is improved to 2.6U
With Low-E glass, the U value is reduced to 1.8U
Where Argon gas is used to fill the air gap, the U value will reduce to 1.6U