Insulating Glass
Low-E Glass Benefits

  • Homeowners save on energy
    costs, for both heating and

  • Comfort is enhanced by
    reducing drafts around
    windows and allowing higher
    room humidity without

  • Builder callbacks and
    potential window
    deterioration due to
    excessive condensation are

  • Fading of interior furnishings,
    such as carpets, drapes, and
    furniture, is reduced.

  • The exterior of the home
    maintains a pleasing
    appearance, and interior
    colors remain true.

  • Homeowners can be assured
    that the glass in their
    windows is backed by the
    strength and experience of a
    leader in the glass industry.

Insulating glass is a glazed unit composed of two or more glass panes
separated by spacers filled with dehydrated air or gas. The sheets are
connected by a spacer, using sealants to reduce water vapor penetration.
The whole unit is hermetically assembled by a secondary edge seal which
gives structural robustness to the insulating glass. The spacer contains a
desiccant which absorbs humidity from within the air space. The insulating
glass unit (IGU) is made manually or with an automatic plant.

Rib Mountain Glass Inc. offers a 10-year insulating glass warranty for most
installation applications and will be happy to provide it to you with your
glass purchase.

Did you know that you can custom design your insulating glass?  We offer
tinted glass as well as many different patterned glasses that can be used
for added UV protection or privacy.
Low-E Glass Features

  • Improves the window U-
    value (provides a higher R-
    value) as compared to
    uncoated glass.

  • Allows the inner pane to
    stay warmer in winter.

  • Reduces room side
    condensation of the

  • Reduces the transmission
    of ultraviolet light.

  • Maintains a natural
    appearance, viewed from
    the outside or inside.

  • Carries a 10-year warranty
    against coating failure.
Rib Mountain Glass Inc.
offers free estimates on
insulating glass
replacement for fogged
or failed units.

For your convenience,
insulating glass can be
replaced on site (for
those large picture
windows) or in our shop.
Have you seen a new home lately? Well, I mean, have you
looked at the windows from the outside at a distance? Did they
appear coated or colored like some new office building? If so,
there probably was Low-E glass in the windows.

Low-E glass is one of the technological marvels of today's
residential construction. Who would have thought 25 years ago
that glass could be coated with an ultra-thin layer of metal?
Who would have guessed that this metal coating would allow
you to see through the glass and provide actual insulating
value? Not me, that's for sure!  Read on for more information.
The E is for Emissivity

My Webster's Seventh New Collegiate Dictionary defines emissivity as "the relative power of a
surface to emit heat by radiation." Emit means to "throw or give off." OK, so Low-E glass
obviously is a special glass that has a low rate of emission. In other words, if there is a heat
source inside your house (or outside!) the glass bounces the heat from that object back away
from the glass. So, in the winter months, if you have Low-E glass in your home, much of the
warmth (heat) given off by the furnace and all the objects which the furnace has heated, is
bounced back into the room.

In the summer, the same thing happens but in reverse. The sun heats things up (the air,
sidewalks, driveways, next door neighbors bricks, etc.)outside of your house. This heat radiates
from those objects and tries to get into your house. Of course it tries to take the path of least
resistance, that being the glass. With Low-E glass much of this heat bounces off the glass and
stays outside.

The Two Types of Low-E

There are two types of Low-E glass: hard coat and soft coat. As you might imagine they have
different properties. In fact, they actually look different.

Hard coat Low-E glass is manufactured by pouring a thin layer of molten tin onto a sheet of glass
while the glass is still slightly molten. The tin actually becomes "welded" to the glass. This
process makes it difficult or "hard" to scratch or remove the tin. Often this glass has a blueish
tint to it.

Soft coat Low-E glass, on the other hand, involves the application of silver, zinc or tin to glass in
a vacuum. The glass enters a vacuum chamber filled with an inert gas which is electrically
charged. The electricity combined with the vacuum allows molecules of metal to sputter onto the
glass. The coating is fairly delicate or "soft."

Furthermore, if silver is used (and it often is) this coating can oxidize if exposed to normal air.
For this reason, soft coat Low-E glass must be used in an insulated glass assembly. Sealing the
soft coating in between two pieces of glass protects the soft coating from outside air and
sources of abrasion. Also, the space between the two pieces of glass is often filled with argon
gas. The argon gas inhibits oxidation of the metallic coating. It also acts as an additional insulator.

The two types of Low-E glass have different performance characteristics. The soft coat process
has the ability to reflect more heat back to the source. It typically has a higher R value. R values
are a measure of resistance to heat loss. The higher the R value of a material, the better its
insulating qualities. Look at Table 1 (on right) for a comparison of R values and the different types
of glass.

Argon is a colourless, odourless, non-flammable, non-reactive, inert gas. Argon gas fills are used
to reduce heat loss in sealed units by slowing down convection inside the air space. Argon gas is
extremely cost-efficient, and works well with Low-e coated glazing.

When we talk about insulating glass without a low-e coating, we refer to glass that uses air
between panes as a primary source of insulation. As air itself is a good insulator, filling the gap
between the glass panes with a low-conductivity gas such as argon improves window
performance by reducing conductive and convective heat transfers. This phenomenon results
from the fact that the density of the gas is greater than the density of the air. Argon is the most
commonly used fill gas, due to its excellent thermal performance and cost-efficiency in
comparison to other gas fills.

Another factor that influences the thermal performance of the IG window is the width of the air
space between the panes of glass. Tests have shown that the optimum efficiency for argon is in
12mm and 14mm IG units.

Several techniques are used to fill the IG cavity. However all techniques result in a mixture of fill
gas and air. It is generally accepted that the IG unit should achieve a 90% fill gas concentration. In
time this concentration will gradually evaporate, at a rate estimated from 0,5 to 1% per year. IG
units filled with argon do not degrade significantly until they reach 75% concentration, which
means up to 20 years of durability.