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How Pilkington K Glass™ works
 How
can a microscopic coating on a pane of glass make such a
big difference?
The glass in your windows absorbs heat then radiates it
again on the colder, exterior, surface. Pilkington K Glass™
has what is called a low emissivity coating on the surface
which faces into the "air gap" of the double glazed
unit.
Low emissivity, or "Low E", means the coating
has poor radiation qualities. The heat absorbed by the coated
glass is inhibited from radiating across the air gap, instead,
the heat is reflected back into the room by the coating.
It works in a similar way to a heat reflector such as aluminium
foil.
Heat losses through different materials are compared by
"U values". The lower the U value, the greater the insulation
properties.
The U value of a single pane window is 5.6. Double glazing
with ordinary glass has a U value of 2.8. Double glazing
with Pilkington K Glass TM has a U value of only 1.9, considerably
better than conventional double glazing, and as good as
triple glazing.
Pilkington K Glass™ should not be used as single glazing.
Appearance
Pilkington K Glass™ has high light transmission and appears
virtually the same as clear float glass. However, in rare
instances of strong oblique lighting, the coating may be
seen as a transparent film. This is simply a transient visual
effect which can be considered positive evidence of the
coated surface being present.
Further evidence of the coating's presence is through the
very minor effect it has on white light transmission. This
effect is so small as to be generally unnoticeable. However,
when a light coloured object or material is in close proximity
to the glazing, dependent on local circumstances and conditions,
a slight darkening can be noted.
Because Pilkington K Glass™ is so neutral in appearance,
it is recommended that its presence in a double glazing
unit is confirmed on installation.
This can be achieved by the use of a coating detector which
unit manufacturers or installers should have available.
In certain extreme environmental conditions, low emissivity
glasses might increase external condensation.
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