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GLAZING

When selecting windows for your home, it’s also important to consider what type of glazing or glass you should use to improve your home’s energy efficiency. Based on various window design factors—such as window orientation, your climate, your building design, etc.—you may even want different types of glazing for different windows throughout your home.

There are many types of glazing available for windows, especially since many glazing technologies can be combined. These window glazing technologies include the following:

Glass with colors

Standard Glass

It is most typically used as transparent glazing material in the building envelop e, including windows in the external walls. Glass is also used for internal partitions and as an architectural feature. When used in buildings, glass is often of a safety type, which includes reinforced, toughened and laminated glasses.

Spectrally Selective Window Glazing or Glass

A special type of low-emissivity coating is spectrally selective. Spectrally selective coatings filter out 40%–70% of the heat normally transmitted through insulated window glass or glazing, while allowing the full amount of light to be transmitted.

Glass with layers and coating

Spectrally selective coatings are optically designed to reflect particular wavelengths but remain transparent to others. Such coatings are commonly used to reflect the infrared (heat) portion of the solar spectrum while admitting a higher portion of visible light. They help create a window with a low U-factor and solar heat gain coefficient but a high visible transmittance. (See energy performance ratings for windows, doors, and skylights for more information on these terms.)

Spectrally selective coatings can be applied on various types of tinted glass to produce “customized” glazing systems capable of either increasing or decreasing solar gains according to the aesthetic and climatic effects desired.

Reflective Window Glazing or Glass

Reflective Window Glazing or Glass

Reflective coatings on window glazing or glass reduce the transmission of solar radiation, blocking more light than heat. Therefore, they greatly reduce a window’s visible transmittance (VT) and glare, but they also reduce a window’s solar heat gain coefficient (SHGC). (See energy performance ratings for windows, doors, and skylights for more information on these terms.)

Reflective coatings usually consist of thin, metallic layers. They come in a variety of metallic colors, including silver, gold, and bronze.

Reflective window glazing is commonly used in hot climates where solar heat gain control is critical. However, the reduced cooling energy demands they achieve can be offset by the resulting need for additional electrical lighting, so reflective glass is mostly used just for special applications.

Low-emissivity

Low-emissivity (Low-E) coatings on glazing or glass control heat transfer through windows with insulated glazing. Windows manufactured with Low-E coatings typically cost about 10%–15% more than regular windows, but they reduce energy loss by as much as 30%–50%.

A Low-E coating is a microscopically thin, virtually invisible, metal or metallic oxide layer deposited directly on the surface of one or more of the panes of glass. The Low-E coating reduces the infrared radiation from a warm pane of glass to a cooler pane, thereby lowering the U-factor of the window. Different types of Low-E coatings have been designed to allow for high solar gain, moderate solar gain, or low solar gain. A Low-E coating can also reduce a window’s visible transmittance unless you use one that’s spectrally selective.

To keep the sun’s heat out of the house (for hot climates, east and west-facing windows, and unshaded south-facing windows), the Low-E coating should be applied to the outside pane of glass. If the windows are designed to provide heat energy in the winter and keep heat inside the house (typical of cold climates), the Low-E coating should be applied to the inside pane of glass.

Insulated Window Glazing or Glass

Insulated window glazing refers to windows with two or more panes of glass. They are also called double-glazed and triple-glazed.

Insulated Glass

To insulate the window, the glass panes are spaced apart and hermetically sealed to form a single-glazed unit with an air space between each pane of glass. The glass layers and the air spaces resist heat flow. As a result, insulated window glazing primarily lowers the U-factor, but it also lowers the solar heat gain coefficient.

Other technologies window manufacturers use to improve the energy performance of insulated glazing include these:

* Gas fills

* Low-emissivity coatings

Heat-Absorbing, Tinted Window Glazing or Glass

Heat Absorber Glass

Heat-absorbing window glazing contains special tints that change the color of the glass. Tinted glass absorbs a large fraction of the incoming solar radiation through a window. This reduces the solar heat gain coefficient, visible transmittance, and glare.

Some heat, however, continues to pass through tinted windows by conduction and re-radiation. Therefore, the tint doesn’t lower a window’s U-factor. However, inner layers of clear glass or spectrally selective coatings can be applied on insulated glazing to help reduce these types of heat transfer.

To improve the thermal performance of windows with insulated glazing, some manufacturers fill the space between the glass panes with gas.

Gas Filled Double Glazing

Window with Gas filled

To improve the thermal performance of windows with insulated glazing, some manufacturers fill the space between the glass panes with gas.

For these gas fills, window manufacturers use inert gases—ones that do not react readily with other substances. Because these gases have a higher resistance to heat flow than air, they (rather than air) are sealed between the window panes to decrease a window’s U-factor.

For more information on how  GLAZING will affect the energy efficiency of your house, or you would like to know more about the service Sustainability WA provide including an Energy Rating or Energy Efficiency certification for your project please contact us here or phone 08 9537 2000

Other terms sometimes used to describe an energy rating includes:  Energy Star, Energy Audit, Energy Ratings, Energy Efficiency Certificate, Energy Assessment, HERS, BER or EPC.

Sustainability WA can help you with them all!


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