Four Remedies for Failed Seals on Insulated Glass Windows

The symptoms of failed window seals are easy to spot. The multi-pane glass develops condensation or fogginess that can’t be wiped off from either side of the window. The cause is a failure in the edge seal that secures the individual panes of glass. This common problem raises two equally common questions: Is there anything you can do about this problem, other than replacing the entire window? and is it really necessary to do anything?

Anatomy of a Thermal Window

A thermal window features two or three panes of glass with open space between the panes. This window assembly is known in the industry as an IGU—an acronym that stands for insulated glazing unit or insulated glass unit. Thermal windows are sometimes called thermopanes or insulated windows.

The space between the glass panes of an IGU is emptied of air by means of vacuum suction, and it is often filled with an inert (noble) gas, such as argon or krypton, to slow the passage of heat through the window unit. Inert gasses are less heat-conductive than air or a vacuumed space.

However, if the seals that protect the edges of the IGU develop a break, then the inert gases can escape and ambient air and moisture can enter the space between the panes, resulting in the IGU losing its extra insulating value. The visible symptom of this failure is the tell-tale fogginess or condensation inside the IGU unit, on the inside surface of the glass. Not only do you lose the aesthetic value of a clear window, but the energy-saving value of the window will be cut dramatically.

IGU Seals

The edges of the glass panes in double- or triple-pane IGU windows are embedded in a sealing material. While it appears to be one seal, it is actually two seals working together. The inner sealant is typically made of polyisobutylene (PIB). The outer sealant is an elastic rubber-like seal that, according to AkzoNobel (a maker of the gases used to fill thermal windows), «functions as an adhesive, holding the glass unit together and keeping it tight during the service life.»

Although these window seals are meant to be long-lasting and may hold up for decades, they can and do fail. Seals can be damaged by house painters using heat guns to strip paint or by homeowners using pressure washers to clean the windows. Improper installation of an IGU window can also cause a seal to fail. But even when there is no such dramatic event, the seals are still destined to fail—eventually. The International Association of Certified Home Inspectors estimates that the gas escapes at a rate of approximately one percent per year under ideal conditions.   This loss of gas can be faster if an IGU is poorly manufactured.

Remedies for Failed Window Seals

Can window seals be repaired if they fail? There are four possible actions to take when you notice the fogginess, condensation, or wavy appearance that signifies the seals have failed on an IGU window.

Call in the Warranty

Premature window seal failure indicates a defective product, and window manufacturers may offer partial or complete replacement of the IGU if the failure occurs within a stated time frame. Other manufacturers may offer prorated compensation in the case of failure, scaled according to the age of the window.

Fix the Fog and Condensation Problem (But Not the Seal)

If there is no warranty protection on the window, there may still be options for making the window look better. Specialty companies have captured this niche by offering defogging services that can make the window more aesthetically pleasing without actually restoring the sealed window spaces. Windows are not removed and replaced; all materials stay in place. Instead, the company drills a tiny hole in the glass and expels the moisture from between the glass panes. Then, an anti-fog solution is applied to the inside of the IGU, a liquid sealant is added to the bottom, and a seal is installed in the drilled hole.

Reviews of defogging are mixed. Inert gasses are not replaced with this process, so the original insulating value of the window is not restored. And the initial seal problem is not corrected unless the seal failure was at the very bottom of the IGU (where the new sealant is applied), so fogginess may well return. Although there are DIY kits available that allow homeowners to try this repair themselves, these are hard to use successfully—the better option is to hire a specialty company. Also, many windows are made with tempered glass, which is very easy to break when drilling, if you don’t know what you’re doing.

Replace the IGU Within the Frame

When an IGU seal fails, you may be able to replace the glass unit itself without replacing the entire window and frame. Glass replacement companies make replacement IGUs that can be installed in existing window frames. Typically, this work is done by professionals, but it’s possible to do it yourself if the window frames are constructed so they can be taken apart. Some windows have screws that join the frame pieces together; others have removable stop moldings that hold the IGU in place within the frame. This is a fairly complicated DIY project, but it can be considerably cheaper than having an entire window replaced.

Leave the Window as Is

If you live in a mild to moderate climate, you may never reap the full benefits that thermal windows have to offer. In many areas, one or two failed window seals in a house with 20 windows will make little difference in the heating or cooling bills. You may well decide to simply live with the window that has a failed seal, provided you can live with the aesthetics of a window that fogs up occasionally.

Tips for Preventing Seal Failure

There are several ways you can help prevent problems with failed seals in thermal windows:

How to Manage a Failed Window Seal

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Older homes may have windows with single-pane glass, but increasingly modern windows sold for new construction or replacement feature some form of sealed glazing. Known as IGUs (insulated glass units), these insulated windows stand at the cornerstone of homes’ energy management system. Over time, the seals on these insulated windows may fail, which compromises the insulating ability, reduces the clarity of the window, and allows more sound to pass into the house.

Construction of Sealed IGU Windows

Sealed windows are constructed with two or three layers of glass assembled to form an IGU (insulated glass unit). Older-style, single-pane windows are not sealed, though sometimes storm windows attached to the home’s exterior gives the impression of double-glazing.

The multiple panes of glass are separated by a spacer material and sealed together at the edges. The space between glass panes is sometimes a partial air vacuum, but more often it is filled with some form of inert gas, such as argon or krypton.

In addition, the glass panes may be coated with a heat-reflective low-E material. This combined technology slows energy transfer so that the IGU windows (with seals intact) keep homes warmer in the winter and cooler in the summer. While nothing in a wall system can be as energy-efficient as a fully insulated wall (with studs and typically fiberglass, foam, or rockwool insulation), a quality insulated two- or three-pane sealed window is a close contender.

How Window Seals Fail

Even in the best of circumstances, the seals on insulated windows are not perfect. Over time, the inert gas inside the units can leak out and moisture from outside air can seep into the space between panes.

One major glass manufacturer Vitro, Architectural Glass (formerly PPG), outlines how window seals can fail:

The partial pressure differentials between the air outside and the gas inside cause both argon and krypton to naturally escape an IGU. Even when an IGU is perfectly constructed, the gas will escape at a rate of about one percent per year, and that rate is much faster when the IGU is poorly made.

Usually, IGU windows experience seal failure gradually in the years following installation in a home. But IGUs are even known to have seal failure even when new.

Transportation over high altitudes such as mountain passes, for example, may cause seal failure due to changes in atmospheric pressure. To avoid this, some manufacturers maintain regional factories so that windows are installed in conditions that are close to those under which they were manufactured.

Checking For Failed Window Seals

Knowing if your windows have seals that have failed is not always easy. Some people believe that you can detect seal failure simply by touching the glass to feel for temperature differences. While this may give you a general idea of the state of your windows, it’s not the sole determining factor. Additionally, there is no tester available on the consumer market that will tell you, conclusively, if your seals have failed; it’s more a matter of deduction.

Clean the Glass

Since detecting seal failure is a visual process, you need to provide yourself with a blank slate. Thoroughly clean both the inside and the outside of the window, so you are certain that you are not looking at external moisture and grime.

Glass Distortion

When the inert gas begins to leak out of the IGU, the panes sometimes begin to bend and collapse slightly in the center, and this can cause the glass to look distorted, or sometimes even break.

By standing at a distance outside and looking at the reflection, you can see if the glass is more distorted than those of windows not affected. Such distortion likely indicates that seal failure has occurred.

Sporadic Condensation

Fogging, hazing, or moisture between the two panes of glass usually means that the window seal has failed. While a window can certainly fail and not have any moisture between the two panes, it is more common to see moisture between the two panes. This fogginess or hazing may come and go, depending on weather conditions. It is most likely to occur when indoor and outdoor temperatures are very different and may vanish as temperatures change or humidity levels change.

Managing Failed Window Seals

File a Warranty Claim

Windows are one purchase where saving the warranty information is very important. Manufacturer warranties can range from 5 years to 15 years or more.

Most window manufacturers warranty their insulated windows against failure in a pro-rated manner so that consumers are reimbursed on a sliding scale depending on the age of the windows. A window that demonstrates seal failure immediately after installation will likely be reimbursed at the full purchase cost, while one near the end of its warranty period will pay less. Manufacturer warranties rarely, though, cover the cost of labor. The labor costs for replacement are usually borne by the homeowner.

Remember that a lifetime warranty does not mean the window is guaranteed for your lifetime or the lifetime of your home. Such warranties cover the expected lifetime of the window itself as defined by the manufacturer.

Make sure to carefully read warranty conditions when you are buying new or replacement windows, and keep all warranty literature.

Living With Fogged Windows

Another option for managing windows with failed seals is to live with the situation. If you live in a moderate climate, your need for sealed IGUs will be less important than if you live in a place of brutal, extreme temperatures.

Weigh the cost of new windows with the increased energy cost, and it may be less expensive to keep the window, failed seal and all. If the window is located in a key area of your home where you spend a lot of time, then you may want to replace the window, after all.

Another compromise is to wait on replacing the fogged window until it’s time to replace a few other windows.

Have the Window Defogged

Another option is to call a defogging company. After drilling a tiny hole in the glass, the company expels the condensation and then installs a valve and seal.

Window defogging is not an inexpensive alternative and results are varied. The process does not generally replace the inert gas inside the IGU, so it does not fully restore the insulating value of the window. It can, however, remove the fogginess and condensation that spoils the look of the window—at least for a time.

Replace the IGU Only

Whether as part of a warranty claim or purchased on your own, the failed IGU unit within the frame can be replaced. Some companies specialize in custom-manufacturing IGU units to specific measurements, though you will need to hire someone to install the IGU once you take delivery. Some companies specialize in the whole process—measuring, manufacturing and installing—but the cost for this is nearly as high as for having the entire framed window replaced.

Replace the Entire Window

Depending on the age of the window, replacing the entire window (frame and all) may be the best option. Sometimes this will be the approach taken if the windows are still under warranty and were installed by the manufacturer’s installation team. This is one instance when labor costs may be covered. More often, this means you’ll be hiring a replacement window firm to install new windows.

Replacing the entire window is the best option when the window is old and the frames and operating hardware may be wearing out anyway. Full replacement can also allow you to take advantage of new technology and energy-saving innovations that might be available. If several windows are demonstrating failed seals, it may be time for a whole-house window replacement project.

Replacement Insulated Glass Unit

Also known as: Sealed window units, Double pane windows, Double glazed units, Sealed Glass Units, Replacement dual pane window units

This product consists of two panes of tempered glass separated by a spacer. The space between the two panes of glass is filled with air. These are most often used in residential window applications. Custom made to your specifications. *See FAQs below for more detail

Description

Sizes:	Minimum 4″ x 4″ Maximum 96″ x 60″
Thicknesses (in):	1/2″5/8″3/4″7/8″1
Shapes:	Almost any shape
Spacer Bar Colors:	Aluminum Champagne Dark Bronze
Grid Colors: (Optional)	Aluminum Champagne Dark Bronze White Tan

Suitable for use in: Residential, Commercial, Retail Grid Profile Options: 5/8″ flat grid or 1” sculptured grid Warranty: 10 year limited warranty Glass Tints: Many glass tint combinations available Production Time Typically 2-5 business days

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More About Insulated Glass Units

Are you looking for a way to consume less energy in your home or office? Sealed Window Units are ideal for cutting costs, while also being better for the environment over single pane windows.

An insulated glass unit consists of two panes of tempered glass separated by a spacer. The space between the two panes of glass is filled with air, which provide insulation. These are most often used in residential window applications.

These are custom manufactured dual pane window units, meant to replace existing windows in your home. You can select glass pane thickness and overall sealed window unit thickness. These can be purchased with or without the white grid between the panes.

Double pane window repair can be easily done by yourself to save money. Most homeowners can perform this kind of window repair on their own without issues. Click here for more info

Benefits of A Dual Pane Insulated Glass Unit

There are several benefits associated with dual pane windows. The most well-known is energy savings, as they are the most common type of energy-efficient residential insulated windows on the market today. Originally intended to protect homes from extreme weather conditions, other benefits have been convincing people to install them with increasing frequency.

Dual pane windows keep the heat out during the hot months and cold out during the cold months, cutting down energy use. To see the best results, select to have glass with a Low-E coating. This coating will significantly boost the efficiency of your replacement window. Additionally, dual pane windows help with noise reduction and can update the appearance of a house while also increasing resale value.

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