When selecting windows for your home, it's 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.
Window Gas Fills
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.
The most common types of gas used by window manufacturers include argon and krypton. Argon is inexpensive, nontoxic, nonreactive, clear, and odorless. Krypton is more expensive but has a better thermal performance.
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).
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.
Insulated Window Glazing or Glass
Insulated window glazing refers to windows with two or more panes of glass. They are also called double-glazed, triple-glazed, and—sometimes more generally—storm windows.
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.
Some window manufacturers use spacers—which separate two panes of glass—that conduct heat less readily than others. These spacers can further lower a window's U-factor.
Low-Emissivity Window Glazing or Glass
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.
There are many types of glazing available for windows, especially since many glazing technologies can be combined. These window glazing technologies include the following:
Laminated glass is a type of safety glass that remains intact when shattered. In the event of breaking, it is held in place by an interlayer, usually made of polyvinyl butyral (PVB) that has been laminated between its two or more layers of glass. This interlayer keeps the layers of glass bonded even when broken.
One of the most appreciated safety benefits is that its high strength prevents the glass from breaking up into large sharp pieces. It's easily recognized by its characteristic "spider web" cracking pattern which results when an impact is powerful enough to crack the glass.
Laminated glass is normally used when there is a possibility of human impact or where the glass could fall if shattered.
In the Florida geographical area, code requires Hurricane-Impact Resistant , laminated glass windows if shudders are not used.