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Thermal
Properties
Service Temperature
Marlon ST Longlife can be installed in a diversity of applications,
with varying temperatures. However, the material's mechanical performance
is known to remain stable in prolonged service in temperatures ranging
from -40°C to +100°C. PVC has a maximum service temperature
of 60°C whilst that of acrylic is 80°C.
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Thermal Expansion
The coefficient of linear expansion of polycarbonate material is
6.7x10-5m/m°C. This is high relative to that of most other materials
in conjunction with which it is normally used. As a consequence
careful allowance must be made for the thermal expansion of Marlon
ST Longlife sheets, both longitudinally and laterally. The table
on page 25 shows the expansion allowances that must be made for
given lengths and widths of sheet.
Insulation
A considerable advantage of Marlon ST Longlife is that it is much
more efficient at preventing excessive heat loss than traditional
glazing materials of comparable thickness. With the emphasis firmly
on energy conservation in modern building practice, Marlon ST Longlife
polycarbonate insulating glazing can be a great asset to the architect
and specifier. The table below compares the insulation properties of Marlon ST Longlife with
other glazing types.
Relative U-Values W/m²ºK
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Marlon ST Longlife |
Single Glass |
Double Glass |
Argon filled cavity |
4 (Twin) |
3.9 |
5.8 |
2.65 |
1.6 |
8 (Twin) |
3.4 |
5.7 |
2.65 |
1.6 |
10 (Twin) |
3.2 |
5.7 |
2.65 |
1.6 |
10 (Four) |
2.5 |
- |
2.65 |
1.6 |
16 (Triple) |
2.4 |
5.5 |
2.65 |
1.6 |
16 (Five) |
1.9 |
- |
2.65 |
1.6 |
16 (M) |
2.2 |
- |
2.65 |
1.6 |
25 (Five) |
1.6 |
- |
2.65 |
1.6 |
30 (Twin) |
2.6 |
- |
2.65 |
1.6 |
32 (XX) |
1.4 |
- |
2.65 |
1.6 |
32 (Seven) |
1.25 |
- |
2.65 |
1.6 |
35 (XX) |
1.4 |
- |
2.65 |
1.6 |
35 (Seven) |
1.2 |
- |
2.65 |
1.6 |
Fitting secondary glazing in front of existing glazing is a very effective
means of achieving energy conservation. Not only does a single sheet
of Marlon ST Longlife itself provide considerable insulation, fitting
Marlon ST Longlife sheets 30-60mm in front of existing glazing, creating
an insulating still air space, provides significant reductions in
heat loss. Typical U-Values are tabulated below.
Thickness (mm) |
U - Value |
Existing Glass |
Marlon ST Longlife |
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W/m2ºK |
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Solar Heat Gain
Some control of heat gain within a building can be achieved using
glazing materials which are designed to influence the nature and quantity
of transmitted light. Marlon ST Longlife with bronze and opal white
tinting are both effective for solar control, reducing glare by diffusing
incoming light and reducing heat gain.
Marlon ST Longlife heat guard is an innovative
development in polycarbonate sheeting which limits
heat build up through the sheet while transmitting
light. It is ideal in any situation where natural light is
required but excessive heat build up can be a
problem.
A 'Heat Guard' option utilises a specially developed pigment to significantly
reduce heat build up through the roof. Heat Guard deflects a much
higher proportion of infra-red radiation than other tint options,
reducing solar heat gain through the roof by up to 50% compared to
other material. "The Institution of Heating and Ventilating Engineers
Guide Book" gives a method of calculating solar heat input through
glazing. The values for shading coefficients when inserted into the
calculations for solar heat input show a reduction in solar heat gain
and consequently in ventilating requirements.
Heat guard opal also reduces solar heat gain
by up to 50% however, the silvery grey colour
is combined with an internal opal surface which
creates a white finish and a soft light quality.
Heat guard opal has a shading coefficient of
0.32 compared to 0.95 for clear material.
Bronze opal combines a bronze external and
opal internal surface. The external bronze surface
blends discretely with other roof finishes while the
opal internal finish provides privacy and soft light
quality. Bronze opal combines the two most
popular tint options.
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