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Window glass has come a long way since the days when only a single pane of glass sat between you and the elements of nature. There are many more options for today’s windows when it comes to glass. Learning about these different options may take some time, but it will surely pay off in increased comfort and energy savings.
If you owned a gas guzzling 1970 Buick, you would surely want to trade it in with gas prices as they are today. Well, windows with one pane of glass literally suck the energy dollars from the home and offer little in protection from heat and cold. Excessive heat loss in the winter months equates to cold drafts and high utility bills. If you have single pane windows with or without a storm window, consider upgrading your windows with today’s insulated glass systems. Because of the poor efficiency with single pane windows, AMSCO only manufactures windows with two or more glass panes.
Insulated glass (IG), a key component for total window performance, offers year-round thermal performance and durability. Insulated glass, also called double glazing, is made up of two panes of glass separated by an air space. The air space provides the insulating value by reducing the transfer of heat flow between the inside and outside. Insulated glass offers several advantages for new construction and replacement window projects, including:
- Improved condensation resistance
- Better sound control
- Increased wind load resistance
- Glass configuration options to control winter heat loss and summer solar heat gain
Warm-Edge Spacer Technology
The material used to create the air space between the two panes of glass in insulated glass is called the spacer. To reduce heat transfer near the edge of a window, low conductance spacers, or warm-edge spacers, are used. Different technologies exist to keep the edge of the windows warmer, preventing heat loss and reducing condensation around the edges of the window.
AMSCO primarily uses the Intercept® Warm-Edge Spacer System by PPG. Intercept spacers feature a unique, one-piece, tin-plated or stainless steel, U-channel design that creates an effective thermal barrier to help reduce conducted heat loss through the window. The sealed, one-piece design makes Intercept spacers stronger and better at retaining the insulating air than many conventional designs. The U-shaped design allows the spacer to flex with the window during temperature changes instead of the sealant. This reduces sealant failure and loss of insulation ability.
Gas Filled IG Units
In some IG units manufacturers will fill the air space with argon or krypton gas. Argon and krypton gas are less conductive than air, which further reduces the heat transfer between the inside and outside. Argon gas is nontoxic, non-reactive, clear, and odorless. Krypton gas has better thermal performance than argon, but is more expensive to produce. The use of a less conductive gas in IG units has insulating benefits but comes at a higher initial cost.
Clear glass in a single pane unit allows for the most heat loss or heat gain based on climate. And, it allows the most visible amount of daylight into the room known as visible transmittance (VT). Clear glass in an insulated glass window reduces solar heat gain but has a visible transmittance similar to single pane units with clear glass.
Low-E Glass Coatings
Low-emittance (Low-E) coatings are virtually invisible, metal or metallic oxide layers deposited on a window glass surface in an effort to reduce the U-factor by suppressing radiated heat flow out the window through the glass. Heat is transferred in a dual paned window by thermal radiation from a warm pane of glass to a cool pane.
||In warm weather, Low-E glass reflects the sun's heat and reduces solar heat gain.
In cold weather, Low-E glass reflects the heat back into the home, reducing heat loss.|
The Low-E coating systems blocks a significant amount of this radiant heat transfer, thus lowering the total heat flow through the window. There are different types of Low-E coatings designed to allow for high solar heat gain, moderate solar heat gain and low solar heat gain.
These different options are utilized in different climates of the country. For instance, cold climates, where heating is primarily used, would utilize the high solar heat gain Low-E coatings. This allows more of the suns heat to come through the windows but the Low-E coating helps to prevent heat escaping from the room. By contrast, warm climates, where cooling is primarily used, would want a low solar heat gain Low-E coating to protect the home from the sun’s heat.
There are various types of tinted glass such as double glazed with high-performance tinted glass and single glazed with bronze or gray tints. One differentiating factor is how much light is passed through – also known as visible transmittance or VT.
Tinted glass has no effect on the U-factor but reduces solar heat gain which may be beneficial in the summer but a liability in the winter depending on where you live.
There are other types of glass available primarily to obscure views while still allowing in light. Different patterns are available to suit almost any style. These glass options are typically used in bathrooms and other rooms where privacy and light is desired.
- Obscure – A pebble-textured obscure glass that is usually a standard offering
- Aquatex – Glass that has an obscure scalloped pattern
- Rain – An obscure glass that gives the illusion of running water down the glass
- Glue Chip – A translucent glass of fine etched glue texture in random patterns
- Narrow Reed – A directional type of obscure glass with a vertical parallel reed pattern
- Hammered - A translucent pattern made to resemble the look of beaten metal
- Delta Frost - A semi-opaque glass with frosted, raised impressions and clear valleys in a random cracked pattern
Laminated glass consists of a tough protective interlayer made of polyvinyl butyral (PVB) bonded together between two panes of glass under heat and pressure. Once sealed together, the glass behaves as a single unit and looks like normal glass. Similar to the glass in car windshields, laminated glass may break upon impact, but the glass fragments tend to adhere to the protective interlayer rather than falling free and potentially causing injury.
Laminated glass is used for safety to deter break-ins and for protection against hurricanes and earthquakes by keeping the broken glass intact within the frame. Laminated glass is also great at reducing sound transmission and is found in airports, museums, schools and libraries to keep out unwanted noise such as from airplanes, heavy machinery and traffic.
To create tempered glass, ordinary glass is heated to around 680 degrees Celsius (1256 degrees Fahrenheit) and then cooled rapidly by blowing air on both sides. This manufacturing process can make the tempered glass up to four times stronger than ordinary glass. When tempered glass breaks, it shatters into small blunt fragments, reducing the risk of serious injury.
Safety codes require tempered glass in all doors (including patio doors) and in windows that are located near doors, bathtubs or showers.