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Breaking it Down: All About Insulated Glass Units (IGUs)

Keeping your home cooler in the summer and warmer in the winter usually comes down to your windows. They are the weakest link in the exterior envelope of your home and the most likely culprit in energy and air leaks. The same brutal elements that impact your roofing and siding also beat down on your windows day in and day out.

While roofing and siding are made from solid, hardy materials meant to withstand the elements, windows are more delicately constructed. They are devices of glass and moving parts housed within a frame. The core element of the window is the insulated glass unit (IGU). For hundreds of year’s, single pane windows were standard. Now it is rare to find an unsealed window. Here is what you need to know about IGUs.

What is an IGU?
These typically consist of two or more flat panes of glass (glass-lites) separated by a spacer and sealed together at the edges. Each pane of glass has two surfaces. So double-glazing has four surfaces and one space between, and triple-glazing has six surfaces with two spaces between. Glass options include clear, low-e, tinted, laminated, reflective, and decorative. They are sealed because the space between contains an air vacuum or a low conductivity gas like krypton or argon. These combinations of two or three panes of glass improve the thermal performance, keeping heat out during the summer and heat in during the winter. And when paired with reflective, low-e coatings the IGUs perform even better.

Additional Benefits of IGUs
Depending on the type of glass and coatings an IGU can be designed for:
• Sound control
• Improved security
• Privacy glass
• Decorative applications
• Bullet resistance
• UV light screening
• Light and solar control
• Hurricane, earthquake, and blast resistance

Gas vs Air in an IGU
Argon and krypton are noble gasses that have more density than air. They are not as reactive and do not conduct as much heat. A 90% argon gas fill will improve the u-value by 16% and a krypton gas fill improves the u-value up to 27%. Unfortunately, the partial pressure differentials between outside air and the inert gas will cause a slow leak. Argon and krypton typically escape at a rate of about 1% per year, even in a perfectly constructed IGU. The lifespan of an IGU will vary depending on the quality of materials and construction, the size of the gap between panes, the surrounding climate, and the temperature differences between the interior and exterior.

How do you Know if a Seal Has Failed?
A failed IGU is typically characterized as foggy, hazy, or milky. So look for moisture or a white scale that cannot be cleaned away. And while some seal failure will not have moisture, it is the most common occurrence. Sometimes the gas leaks out and the space does not backfill with air. In these cases the two lites can distort as they start to collapse towards each other in the center. The lites may even break.

Why Does Seal Failure Matter?
In a moderate climate, seal failure may not be such a big deal. But in an extreme climate, like that of Phoenix, AZ, a failed seal will definitely impact energy efficiency and comfort. Glazing or full replacement windows Mesa, AZ is the best solution. For an evaluation and quote, contact Freelite. Call today at (602) 233-1981 or stop by 331 W. McDowell Rd., Phoenix, AZ 85003 to talk with one of our experts.