Double Glazing, Replacement Windows -
Pilkington K Glass, Low E Glass, Suncool Glass.
What is the U Value of a typical Double
Glazed sealed unit?
The following table shows some typical U values
for vertical insulating glazing Pilkington Insulating Units and the effect
of using K Glass, Argon and varying cavity widths. The lower the U Value -
the better the insulator. U-value is the measurement of heat transfer
through a given building material, glass, etc. In the UK all U Values are
quoted as W/m²K.
Glass
Specification
Cavity
width
12 mm
16 mm
20
mm
Optifloat/air/Optifloat
2.9
2.7
2.8
Optifloat/argon/Optifloat
2.7
2.6
2.6
Optifloat/air/Pilkington K
Glass
1.9
1.7
1.8
Optifloat/argon/Pilkington K
Glass
1.6
1.5
1.5
Overall width of Insulight
Unit (mm)
20
24
28
U values based upon 4mm Pilkington Optifloat
thickness. (NOTE: Optifloat is the name given by Pilkington to "normal"
float glass)
Figures determined in accordance with the requirements
of BS EN673: 1998 for `normal' exposure conditions. U values are rounded
to the nearest 0.1W/m2K as described in clause 9 of the standard. The
total overall U value of a window can be calculated taking into account
the insulation of the glazing, the unit spacer and
framing.
We often get asked what is the best cavity width to
use in a double glazed sealed unit. As can be seen above there is very
little difference between a 16 mm and 20 mm cavity.
You will also
note that adding Argon Gas alone has very little effect in improving the U
Value. Only when the Argon is combined with Pilkington K Glass is any
significant improvement made.
SPECIAL NOTES
Pilkington
are only one of many glass suppliers world-wide. We are only giving
their products so much prominence here because of their large market
share in the UK.
If you live in
Australia we suggest you have a look at the Pilkington - Australia
web site at http://www.pilkington.com.au
Different parts
of the world quote U Values in different ways. In the UK all U
Values are quoted as W/m²K. The lower the U Value - the better the
insulator. U-value is the measurement of heat transfer through a
given building material, glass, etc
Double-Glazing-UK.co.uk -
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