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THE ‘E’ IN
LOW-E
The ‘E’ in low-E refers to emissivity. Emissivity
is a measure of a material’s ability to radiate energy.
A material with ‘low’ emissivity absorbs and
radiates infrared energy poorly which is the key factor
in reducing heat transfer.
The lower the emissivity of a coating the better the glass performs in
reducing heat transfer.
HOW DOES LOW-E GLASS WORK ?
A basic understanding of how low-E glass works, involves a closer look
at the sun’s energy and the solar spectrum.
The sun’s energy can be divided into different components such as
(1) ultraviolet light; (2) visible light; (3) infrared energy.
High levels of ULTRAVIOLET LIGHT can be harmful to humans and damage and
fade furnishings. The desire is to exclude all of this component.
VISIBLE LIGHT is the desirable component giving us natural daylight, the
cheapest source of lighting available (of course we may want to control
glare).
The INFRARED ENERGY component may be both desirable and undesirable. It
is desirable when we seek sunshine and warmth for personal comfort and
to naturally heat a room’s interior (passive solar heat gain/heating).
It is undesirable when it becomes discomforting, where the room becomes
hot and strains are placed on people and air-conditioning systems.
The infrared part of the spectrum (or what we feel as heat) consists of
varying wavelengths. Short wave infrared heat energy is absorbed in the
interior of the building by carpets, curtains, furniture, walls etc., and
is changed into long wave infrared heat. Objects outside the building also
absorb short wave energy and are changed into long wave heat energy.
The special coating on Sungate 500 low-E glass reflects long wave heat
radiation back into the room in winter conditions and for summer conditions
reflects heat back outside.
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Low-E
glass selectively allows specific portions of the sun’s
energy or the ‘desirable’ wavelength components
to be transmitted. When combined with spectrally selective
tinted glass such as Azurlite and Solargreen, low-E glass
offers the ideal glazing solutions of low ultraviolet
and high visible light transmittance, low shading co-efficient
or solar gain and high insulation or ‘U’- values.
This translates to a greater control of the internal
environment, greater occupant comfort and lower heating
and cooling costs.
FEATURES AND APPLICATIONS
 helps
reduce summer heat gain and winter heat loss;
reduces
ultra-violet substantially;
improves
occupant comfort, reduces condensation build up;
coating
is transparent, non reflective and durable (hard coat);
best
performance achieved in double glazed units (IGU’s);
available
in 3, 4 and 6mm annealed, toughened and can be laminated.
DID YOU KNOW?
performance
of this product is best achieved with IGU’s;
climate
condition determines position of coated surface in
glazing (refer text);
coatings
may effect the colour of the glass. Samples should be viewed;
toughening
or heat strengthening will prevent thermal breakage;
for
more information on the thermal safety of Annealed glass,
refer Thermal Breakage.
SUNGATE® 500
Pyrolytic (hard coat) coated glass such as Sungate® 500 are produced
at the molten stage of float glass manufacture, where a tin oxide coating
with additives is applied to the glass. Upon cooling, this coating is fused
into the body of the glass. The surface produced is as durable as normal
glass in terms of cutting, processing and installation. The glass can be
heat strengthened, toughened or laminated like normal float glass.
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SURFACE
POSITIONS FOR IGU'S
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COMMON
LOW-E TRADE NAMES
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ClevaCoat – China
Southern
Comfort
E – AFG/AFGD
Ekoplus – St
Gobain
4mm and 6mm hard coats.
Energy Advantage Low E – LOF
K-Glass – Pilkington
Hard coat.
Sungate – PPG
Range of 3, 4 and 6mm hard coats and soft coats. |
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Single
glazing is a poor insulator. In warm climates single
glazed clear glass will let through a major proportion
of the sun’s energy making the room
hotter. Having windows exposed to direct solar energy will increase cooling costs.
In colder climates the warmth that may be generated in a room quickly transfers
to the colder outside, increasing heating costs. Products with a low emissivity,
or low-E coating, such as PPG’s Sungate® were specifically designed
to reduce heat transfer in warmer and colder climates and reduce energy costs.
Low-E glass works most efficiently in insulated glass units. This product is
generally non-reflective and
highly transparent. (eg., 77% visible light transmittance for PPG Sungate® 500.) |
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