Types of window glass

Modern types of windows have new types of glass panes with low-E coatings, inert gas fills, low-conductivity spacers and eventually thin sheets of special films.

The simplest way to select a window (and their glass panes) is to take into account its rating label and the information that it contains. But understanding some basics about the types of glass and their properties will help you make an informed decision…

See also: Best residential window rating
Effectiveness of the new types of window glass
New windows are very effective at... 1) ... keeping the heated and cooled air inside the home (something that is assessed by the insulating value or U-value of the window glass…); 2) ... controlling the degree of heat coming from sunlight (measured by the SHGC or Solar Heat Gain Coefficient of the window glass) and... 3) ... controlling the sun's light (measured by the VT, or Visual Transmittance coefficient) and condensation (measured by the window's Condensation Resistance coefficient).

New window & glass panes

New windows are based in two (or three) glass panes associated to low-e coatings and spacers

Single clear glass is a thing of the past. It’s too inefficient.

Modern windows have 1) two or even three glass panes associated to 2) low-E coatings, 3) inert gas fills and 4) spacers...

Low-E Coating Window glass (Low-emissivity coating glass)

Low-E coating glass is a thin-invisible metallic layer, often applied to the exterior face of the interior glazing (in the typical case of two-pane window glass).

A double-pane window with a low-E coating can be as efficient as a triple-glazed unit without the coating, with a huge advantage: lower weight that makes the windows easier to operate and reduces wear and tear on the window's hinges, cranks and other parts…

Low-E coatings are also a mean of controlling UV rays and visibility, and vary with climate.

There are now many different types of low-E coatings with different features, namely low-E coatings for cold climates (to maximize solar heat gains and also to reduce heat loss at night) and low-2E coatings (or solar control low-E coatings) for hot climates (and for west or east-facing windows in cold climates).

Solar control low-E coatings are often tinted glasses, that is, glasses containing special tints that change their color in order to absorb a larger fraction of solar radiation, reducing the solar heat gain and visibility. Green and blue-tinted are very common types of window glass in hot climates. Black-tinted glass is often avoided because of its lower absorption of heat and large absorption of light...

Inert Gas Fills (Argon and krypton)

Whatever the type of glazing, filling the space between the glass panes of the window with an inert gas (usually argon or krypton) is particularly important for energy-efficiency.

Krypton is thermally more efficient than argon, but it’s more expensive. Argon is the standard solution.

Low-Conductivity Spacers

New two- and three-glass pane windows have spacers between them, at their perimeter, to seal the gas space between the frames.

Traditionally, these spacers where made out of hollow aluminum, but there is now new alternatives involving new materials that can improve the efficiency of multi-pane low-E coating windows. Pay attention to this detail.

Special Window Films

Some types of window glass combine low-E coatings with thin sheets of transparent films (usually made out of polyester). These films are typically designed for hot climates or west and east-facing windows, where solar gains and glare are a problem.

See: Sun reflective window films