clear energy glass mini Glass heat preservation, Built-in desiccant
Installing windows containing energy-efficient double or triple
glazed units provides you with many benefits:
- Improves the energy-efficiency of your home
- Reduces the amount of energy you use
- Saves you money on your heating bills
- More effective than single glazing or standard double glazing
- Provides you with the quality and reassurance you would expect from
a leading brand
- Manufactured to the highest European quality standards
- Available from window installers countrywide in a range of frame
How does Energy Saving Glazing work?
Heat always flows towards the cold. Therefore, window glass without
a low-e coating will absorb the heat from your home and radiate it
onto the colder outside surface, where it is lost. Low-e glass has
a special coating which is a poor radiator of heat and does not
allow heat to be transferred to the outside. Instead, the low-e
coating actually reflects the heat back into your room.
- ome of the energy is absorbed by the glass as it passes through.
The absorbed energy heats the glass. The energy that has entered
the living space is also absorbed by the items in the room such as
furniture and carpets. These items also get warmed by the energy.
- Warm items re-radiate the energy and this includes fires and
radiators within the room as well as the warmed furniture. This
re-radiated energy is no longer short wave radiation so the energy
now travels back towards the low-e window as long wave radiation.
- The low-e glass does not let the longer wavelength radiation emit
from the coated low-e surface and is an effective reflector. The
energy that has entered the room and the heat energy that was
already present is reflected back from the low-e glass. Even the
glass that was heated by the energy passing through it emits long
wave energy and it can send it in two directions. Some is sent back
out into the atmosphere and some to the inside of the building.
- The result is a neutral appearance glass that lets energy in and
helps prevent heat getting out.
By placing low-e glass into a double or triple glazed unit, the
individual glass pane temperatures change. As more heat is
retained, the outer pane of glass is not heated as much by escaping
energy and the inner pane is keeping more heat in and becomes
warmer. This has two effects. There are less cold draughts from
convection near the windows and the risk of condensation on the
glass is reduced. In this way, low-e glazing not only prevents heat
loss, but also encourages warmth during the colder months of the
U-value of energy-efficient glazing
The rate at which glass transmits heat out of the building is
measured by the U-value. U-value is measured in W/m2K (Watts per
square metre per Kelvin temperature difference). The larger the
figure, the greater the heat loss.
Example of heat loss saving
If you have a house that has 20m2 of glass and its U-value is 5.8
(single glazing) and it is 10 degrees colder outside than inside
then you will be losing 1160 Watts (=5.8 X 20 X 10). This is a rate
of loss greater than one bar on an electric fire. By replacing the
glass with a low-e product the U-value might become 1.5 so you are
now only losing 300 Watts (almost a quarter of the heat loss).
Improved window seals and draft proofing will also improve the
overall insulation properties of the window saving even more
energy. The other aspect of energy efficiency is the ability of the
glass to transmit heat. The U-value of the property and the rate at
which heat is allowed into the building is a more thorough
evaluation of the effectiveness of the glass. The total
transmittance of the glass (or more correctly the total solar heat
transmittance or g-value) is the value given to the glass. The
higher the figure the better for gaining heat which is the
objective in most domestic situations. Low-e glass types can be
compared using the U-value and the g-value.
Another measure that is used for comparing low-e glass types is the
shading coefficient. Shading coefficients compare the solar heat
transmittance properties of the glass by short and long
wavelengths. The proportion of energy that each glass allows
through is compared back to a standardised thin piece of clear
glass with known properties. Shading coefficients are given for the
short wave energy, long wave energy and the two combined into the
total shading coefficient. A glass with a relatively high long wave
shading coefficient will have absorbed a lot of energy and be
re-radiating it into the building. It is likely to be a coloured,
highly absorbing glass. This information is of particular interest
to architects and also heating and ventilation engineers, as they
can calculate the heating and cooling loads for a building when
they know how much energy will either come through or escape from a