Types of glass
- Pick self-cleaning glass for low maintenance
- Check out U values
- Choose glass according to position of window
There are a number of options when it comes to choosing
the glass in your double-glazed unit – from plain
to patterned, coloured, stained and a number of ‘speciality’ glasses.
Your choice will depend on your house style, your budget,
your taste and the position of the window.
Low E Glass
Low-e glass stands for low emissivity glass. This glass
varies from normal clear glass in that one side of
the glass has a special metal coating, technically known
as a low emissitivity, or Low E. coating. Low-E glass
is a type of insulating glass, which increases the
efficiency of windows by reducing the transfer of heat
or cold through glass. That means in the winter your
house stays warmer, and in the summer it stays cooler.
There are two types of Low-E (low emissivity) glass available
- Pyrolytic (hard coat) is considered to be a medium performer,
and sputtered (vacuum deposition or soft coat) is considered
to be the highest performer.
Pilkington K Glass™ (A Brand of Low E Glass)
The most common is Pilkington K Glass™ which has
high light transmission and appears virtually the same
as clear float glass.
It is the microscopic coating that makes the big difference
to its performance. Glass in a window absorbs heat then
radiates it again on the colder, outside, surface. Pilkington
K’s low emissivity coating on the surface that faces
into the air gap of the double glazing unit provides a
poor radiator. The heat absorbed by the coated glass is
inhibited from radiating across the air gap and then from
the outer pane to the cold outside world. Instead the heat
is reflected back into the room by the coating.
It works in a similar way to a sheet of reflecting foil
placed behind a central heating radiator which bounces
the heat back into the room. Heat losses through different
materials can be compared by their U values. The higher
the U value, the greater the heat loss through the material.
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™ has a U value of only 1.9,
considerably better than conventional double glazing, and
as good as triple glazing.
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.
What took them so long? Pilkington Activ™ is the
holy grail of glass. Its active coating, chemically bonded
onto its outside surface, is designed to absorb the ultraviolet
light given off by the sun.
This absorption process causes a reaction on the surface
of the glass, which breaks down and loosens dirt. Then,
when it rains, the coating causes rain water to 'sheet'
off the surface of the glass, which not only washes away
the loosened particles of dirt, but also prevents the formulation
of droplets, which cause streaks and make windows look
SGG PLANITHERM (A Soft Coat Low E Glass)
SGG PLANITHERM is a clear float glass, which has been
coated with metallic oxides by magnetically enhanced cathodic
sputtering under vacuum conditions.
This sputtered coating is highly reflective to long-wave
heat radiation, otherwise known as a "low emissivity" or
low-e coating. This greatly reduces heat loss and ensures
that double-glazed units incorporating SGG PLANITHERM provide
excellent thermal insulation.
SGG PLANITHERM is neutral in appearance and has a high
light transmittance factor.
Neutral Appearance has these main benefits:
No unsightly tint
Unlike traditional low-E coatings that suffer from an unsightly
yellow tint, SGG PLANITHERM looks very clear. This means
your curtains or Georgian Bars will not look dirty or
less tint also means more light can enter the room, making
it more comfortable and luminous
No 'haze' effect
SGG PLANITHERM does not suffer from the unsightly tint
commonly associated with traditional low-E products
SGG PLANITHERM is a slightly more difficult product to
locate than say the Pilkington Products, so you may have
to ask your supplier to specially source it for you, if
having a neutral appearance is very important to you.